Co-reporter:Dandan Guo;Chaoyan Lou;Meilan Chen;Binghe Zhu;Peimin Zhang;Nani Wang
Analytical Methods (2009-Present) 2017 vol. 9(Issue 19) pp:2840-2844
Publication Date(Web):2017/05/18
DOI:10.1039/C7AY00906B
Dimethyl carbonate (DMC) is widely used in solvents, fuels, monomers, and synthesis. The inorganic anions in DMC always have a big impact on product performance. Herein, improvement in the performance of the conventional column-switching technique and on-line elimination pretreatment system was achieved to automatically determine trace anions in DMC. In this study, a pretreatment column was applied to eliminate the DMC matrix on-line, and target anions were eluted from the pretreatment column and retained in the concentrator column. The collected anions were eventually separated in the analytical column using the column-switching technique. Eluent containing 100% acetonitrile was used to wash out DMC and regenerate the pretreatment column at the same time. A type of water-soluble solvent was added to the DMC samples before injection to help improve their solubility in the eluent, which was subsequently removed by extending the collection time in the concentration procedure. This method shows satisfactory linearity (R2 ≥ 0.9977) in the range of 0.1–8.0 mg L−1. The detection limit based on the signal-to-noise ratio of 3 (S/N = 3) is 2.79–5.66 μg L−1. The recovery rate for the anions is 85.09–99.07%. Good reproducibility was obtained with relative standard deviations less than 4.03% by injecting standard solutions 6 times.
Co-reporter:Feng-Lian Wang;Yong-Gang Zhao;Nadeem Muhammad;Shu-Chao Wu
RSC Advances (2011-Present) 2017 vol. 7(Issue 52) pp:32769-32776
Publication Date(Web):2017/06/23
DOI:10.1039/C7RA00867H
A rapid and simple approach involving two-dimensional ultrahigh-performance liquid chromatography (UHPLC) combined with ion chromatography (IC) through valve-switching was developed to determine parabens and inorganic anions in cosmetics simultaneously. Compared with a conventional IC column-switching technique, the proposed method required UHPLC coupled with IC via valve-switching without refreshing the pretreatment column. In this chromatographic system, a mobile phase with 60% methanol and 40% deionized water was used to simultaneously separate parabens, namely, methylparaben (MP), ethylparaben (EP), propylparaben (PP), and butylparaben (BP), and to eliminate the matrix, and KOH eluent (20 mmol L−1) was utilized to separate inorganic anions, such as nitrite, sulfite, sulfate, and nitrate. Organic compound analysis, and inorganic anion pretreatment and analysis were simultaneously performed with a single injection. Under optimized conditions, matrix–calibration curves were examined by preparing and analyzing different concentrations of mixture standard solutions containing parabens and inorganic anions. Linearity was between 0.9994 and 0.9999. The limits of detection ranged from 8.0 to 80 μg L−1. Satisfactory recoveries of cosmetic samples were obtained between 93.9% and 106.2% by adding three representative standard solutions. The proposed method can be applied to routine analysis, as indicated by the validated linearity, accuracy, and precision and potential application on the analysis of MP, EP, PP, BP, nitrite, sulfite, sulfate and nitrate in eight commercial samples.
Co-reporter:Dandan Guo, Chaoyan Lou, Nani Wang, Meilan Chen, Peimin Zhang, Shuchao Wu, Yan Zhu
Talanta 2017 Volume 168(Volume 168) pp:
Publication Date(Web):1 June 2017
DOI:10.1016/j.talanta.2017.03.053
•A new HPLC column was synthesized by grafting with PAMAM dendrimers.•Polymer matrix improved the chemical and thermal stability of the stationary phase.•Rich surface groups of PAMAM dendrimers result in a good resolution of the column.•Benzene rings attraction and amino repulsion mechanism ensure the rapid separations.A novel high performance liquid stationary phase was prepared by grafting poly amidoamine (PAMAM) dendrimers to poly (styrene-divinyl benzene-glycidylmethacrylate) matrix in this work. Different generations of PAMAM dendrimers grafted to polymer matrices containing different glycidylmethacrylate amounts by reacting with epoxy groups in glycidylmethacrylate molecules. The synthesized PAMAM dendrimers and stationary phase were characterized by fourier transform infrared spectroscopy, scanning electron microscope, N2 adsorption/desorption, elemental analysis and thermo gravimetric analyzer. The proposed stationary phase was suitable for rapid separation of phenylene diamine isomers and aminobenzene. The separation mechanism of benzene rings attraction and amino repulsion was verified by retention behaviors of methylamine, phenylamine, phenylene diamine, naphthylamine and toluene. The reliability of the stationary phase was demonstrated by separation and determination of phenylene diamine isomers including m-phenylene diamine, o-phenylene diamine and p-phenylene diamine in hair dye precursors within 10 min. Satisfactory resolution and short analysis time make the columns promising for determination of aniline compounds in various fields.Download high-res image (102KB)Download full-size image
Co-reporter:Chaoyan Lou, Dandan Guo, Nani Wang, Shuchao Wu, Peimin Zhang, Yan Zhu
Journal of Chromatography A 2017 Volume 1500(Volume 1500) pp:
Publication Date(Web):2 June 2017
DOI:10.1016/j.chroma.2017.04.029
•A membrane-based distillation (MBD) module was fabricated for sample preparation.•MBD module consists of a sample vessel and a lab-made membrane unit.•MBD was hyphenated with IC to implement on-line detection of fluoride.•Successful application of this method in serum and urine.An online membrane-based distillation (MBD) coupled with ion chromatography (IC) method was proposed for automatic detection of trace fluoride (F−) in serum and urine samples. The system consisted of a sample vessel, a lab-made membrane module and an ion chromatograph. Hydrophobic polytetrafluoroethylene (PTFE) hollow fiber membrane was used in MBD which was directly performed in serum and urine samples to eliminate the matrix interferences and enrich fluoride, while enabling automation. The determination of fluoride in biological samples was carried out by IC with suppressed conductometric detection. The proposed method feasibly determined trace fluoride in serum and urine matrices with the optimized parameters, such as acid concentration, distillation temperature, and distillation time, etc. Fluoride exhibited satisfactory linearity in the range of 0.01–5.0 mg/L with a correlation coefficient of 0.9992. The limit of detection (LOD, S/N = 3) and limit of quantification (LOQ, S/N = 10) were 0.78 μg/L and 2.61 μg/L, respectively. The relative standard deviations of peak area and peak height were all less than 5.15%. The developed method was validated for the determination of fluoride in serum and urine with good spiked recoveries ranging between 97.1–101.9%. This method also can be proposed as a suitable alternative for the analysis of fluoride in other complex biological samples.
Co-reporter:Nadeem Muhammad, Qamar Subhani, Fenglian Wang, Dandan Guo, Qiming Zhao, Shuchao Wu, Yan Zhu
Journal of Chromatography A 2017 Volume 1515(Volume 1515) pp:
Publication Date(Web):15 September 2017
DOI:10.1016/j.chroma.2017.07.007
•A flexible column-switching IC system was fabricated for matrix elimination.•QuEChERS method used for extraction of pharmaceutical drugs from complex samples.•All drugs were isocratically separated and detected with fluorescent detector.•Validated results were acceptable for all five analytes in three complex samples.This work illustrates the introduction of a simple, rugged and flexible column-switching ion chromatography (IC) technique for an automated on-line QuEChERS extracted samples extracts washing followed by sensitive fluorescence (FLD) determination of five acidic pharmaceutical drugs namely; clofibric acid (CLO), ibuprofen (IBU), aspirin (ASP), naproxen (NAP) and flurobrofen (FLU) in three complex samples (spinach, apple and hospital sewage sludge). An old anion exchange column IonPac® AS11-HC was utilized as a pre-treatment column for on-line washing of inorganic and organic interferences followed by isocratic separation of five acidic drugs with another anion exchange IonPac® AS12A analytical column by exploiting the column-switching technique. This novel method exhibited good linearity with correlation coefficients (r2) for all drugs were in the range 0.976–0.996. The limit of detection and quantification of all five acidic drugs were in the range 0.024 μg/kg to 8.70 μg/kg and 0.082 μg/kg to 0.029 mg/kg, respectively, and better recoveries in the range 81.17–112.5% with percentage relative standard deviations (RSDs) less than 17.8% were obtained. This on-line sample pre-treatment method showed minimum matrix effect in the range of 0.87–1.25 except for aspirin. This simple rugged and flexible column-switching system required only 28 min for maximum elimination of matrices and interferences in three complex samples extracts, isocratic separation of five acidic drugs and for the continuous regeneration of pre-treatment column prior to every subsequent analysis. Finally, this simple automated IC system was appeared so rugged and flexible, which can eliminate and wash out most of interference, impurities and matrices in complex samples, simply by adjusting the NaOH and acetonitrile concentration in washing mobile phase with maximum recoveries of acidic analytes of interest.
Co-reporter:Kai Zhang, Minyi Cao, Chaoyan Lou, Shuchao Wu, Peimin Zhang, Mingyu Zhi, Yan Zhu
Analytica Chimica Acta 2017 Volume 970(Volume 970) pp:
Publication Date(Web):1 June 2017
DOI:10.1016/j.aca.2017.03.015
•Graphene-coated polymeric particles were fabricated by a facile method.•Hyperbranched condensation polymers (HBCPs) were grafted from graphene-coated particles to make anion exchangers.•Graphene amount and HBCPs layer count had significant effects on the anion exchange capacities.•Separation of diverse anionic analytes on the anion exchangers was demonstrated.•The prepared anion exchangers exhibited high stability.Carbonaceous stationary phases have gained much attention for their peculiar selectivity and robustness. Herein we report the fabrication and application of a graphene-coated polymeric stationary phase for anion exchange chromatography. The graphene-coated particles were fabricated by a facile evaporation-reduction method. These hydrophilic particles were proven appropriate substrates for grafting of hyperbranched condensation polymers (HBCPs) to make pellicular anion exchangers. The new phase was characterized by zeta potentials, Fourier transform infrared spectroscopy, thermogravimetry and scanning electron microscope. Frontal displacement chromatography showed that the capacities of the anion exchangers were tuned by both graphene amount and HBCPs layer count. The chromatographic performance of graphene-coated anion exchangers was demonstrated with separation of inorganic anions, organic acids, carbohydrates and amino acids. Good reproducibility was obtained by consecutive injections, indicating high chemical stability of the coating.Download high-res image (196KB)Download full-size image
Co-reporter:Dan Wei;Xu Wang;Nani Wang
RSC Advances (2011-Present) 2017 vol. 7(Issue 10) pp:5920-5927
Publication Date(Web):2017/01/16
DOI:10.1039/C6RA25711A
A simple and rapid column-switching ion chromatography with non-suppressed conductivity detection method was developed for simultaneous determination of L-carnitine, choline and mineral ions (free sodium, potassium, magnesium and calcium ions) in milk and powdered infant formula samples. On-line sample clean-up was achieved on the pretreatment column Dionex IonPac NG1 (50 mm × 4 mm, i.d.), with pretreatment elution (3 mmol L−1 MSA) and washing solution (100% acetonitrile) at a flow rate of 1.0 mL min−1. After column switching, the separation and determination of analytes were performed using guard column Dionex IonPac SGS (50 mm × 4 mm, i.d.) and analytical column Dionex IonPac SCS (250 mm × 4 mm, i.d.) with an isocratic mobile phase consisting of 3 mmol L−1 MSA and 10% (v/v) acetonitrile, at flow-rate of 1 mL min−1, followed by non-suppressed conductivity detection. The organic matrices clean-up performance of the proposed method was studied using an UV detector working at 200–400 nm. Under the optimal conditions, detection limits (S/N = 3) ranging from 0.05–0.30 mg L−1, good linearities in the range of 1–100 mg L−1 with a correlation coefficient over 0.9973, and satisfactory recoveries in the range between 94% and 105% with relative standard deviation less than 2.1% for real samples were attainted. The proposed method was successfully applied to rapid, simultaneous, and labour-saving detection of L-carnitine, choline, and mineral ions in milk and powdered infant formula samples.
Co-reporter:Dan Wei;Shuchao Wu
RSC Advances (2011-Present) 2017 vol. 7(Issue 70) pp:44578-44586
Publication Date(Web):2017/09/11
DOI:10.1039/C7RA08203G
A magnetic solid-phase extraction (MSPE) based on graphene oxide/nanoscale zero-valent iron (GO/nZVI) coupled with high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was proposed for the determination of trace tetracycline antibiotics (TCs) in water and milk. GO covered nZVI was self-assembled by electrostatic forces by varying the pH. Several important parameters affecting the MSPE procedure have been investigated. The pH value is a key factor in the whole MSPE process. An appropriate pH can not only improve adsorption and desorption efficiency, but also enable the extraction of TCs from GO/nZVI by using deionized water. Optimal conditions were then used for the extraction of TCs from real samples, prior to HPLC-MS/MS determination in the positive ESI mode of multiple reaction monitoring (MRM) using a ZORBAX Eclipse Plus C18 column. The proposed method achieved low limits of quantitation in the range of 8.05–83.19 ng L−1 and 17.42–182.75 ng L−1 for water and milk samples, respectively, and satisfactory recoveries in the range of 84.2–105.5% with intra-day RSD in the range of 0.6–2.5% and inter-day RSD in the range of 1.2–9.2% for the spiked water sample and from 87.0% to 101.8% with intra-day RSD in the range of 1.1–5.4% and inter-day RSD in the range of 2.0–9.7% for the spiked milk sample.
Co-reporter:Nadeem Muhammad;Weixia Li;Qamar Subhani;Fenglian Wang;Yong-Gang Zhao
New Journal of Chemistry (1998-Present) 2017 vol. 41(Issue 17) pp:9321-9329
Publication Date(Web):2017/08/21
DOI:10.1039/C7NJ01757J
The aim of this novel study was to introduce a cheap, simple, sensitive, and green methodology involving the dual application of synthesized porous SnO2 nanoparticles (NPs) for selective conversion of non-fluorescent ketoprofen (KP) into a highly fluorescent species and as a sorbent in a μ-sample preparation method for extraction of KP from the three complex human serum, urine, and canal water samples. The clean separation and sensitive fluorescence determination of KP from these complex samples were carried out by coupling an ion chromatograph with a fluorescence detector (IC-FLD). The sorbent was prepared by a simple chemical precipitation method in water and characterized via various techniques. The porous SnO2 NPs, in addition to their role in the selective conversion of KP into a highly fluorescent species, also act as an effective sorbent for the selective degradation and elimination of polar organics, inorganic matrices, and heavy metals in complex samples. The optimized analytical method exhibited satisfactory linearity for ketoprofen in the concentration range of 0.2–1.5 mg kg−1 with a correlation coefficient (r2) of 0.997. The limit of detection (LOD) and quantification (LOQ) in human serum, urine, and canal water samples were 0.1 μg kg−1, 0.5 μg kg−1, and 0.39 μg kg−1 and 1.3 μg kg−1, 0.3 μg kg−1, and 1.7 μg kg−1, respectively. The method also showed good intra-day and inter-day precisions at the two concentration levels of 0.5 mg kg−1 and 1.3 mg kg−1 in complex samples with the relative standard deviations (RSDs) less than 16.3% (n = 5), and satisfactory recoveries were retrieved in the range of 85.1–101.4% with minimum or no matrix effect.
Co-reporter:Yong-Gang Zhao;Yun Zhang;Feng-Lian Wang;Ning Chen;Chao-Yan Lou;Kai Zhang;Mi-Cong Jin
Analytical Methods (2009-Present) 2017 vol. 9(Issue 29) pp:4234-4239
Publication Date(Web):2017/07/27
DOI:10.1039/C7AY00894E
In China, air pollution is getting worse, and the adverse effect of formaldehyde on human health has been attracting more and more attention. The present work proposes a novel, fast and sensitive analytical method for the determination of formaldehyde in the air of public places. This method was based on the determination of the 3-methyl-2-benzothiazolinone hydrazone (MBTH)–formaldehyde condensation product of the derivatization between formaldehyde and MBTH. The actual formaldehyde concentration in air was determined by leading the test atmosphere through a bubble absorption tube containing the MBTH absorption solution and subsequent liquid chromatography-tandem quadrupole mass spectrometry (LC-MS/MS) analysis. Recoveries of spiked formaldehyde samples were in the range of 92.2–106% with relative standard deviations (RSDs) less than 5.0%. The limit of detection (LOD) of formaldehyde in air samples was 0.05 μg m−3, which was much lower than that of the state standard method of China for the determination of formaldehyde in the air of public places (5.6 μg m−3). The satisfactory validation results and the application to the analysis of formaldehyde in the air of a hotel and subway station demonstrated the applicability to air quality monitoring analysis.
Co-reporter:Qiming ZhaoShuchao Wu, Peimin Zhang, Yan Zhu
ACS Sustainable Chemistry & Engineering 2017 Volume 5(Issue 1) pp:
Publication Date(Web):November 28, 2016
DOI:10.1021/acssuschemeng.6b00802
Carbonaceous nanospheres (CNSs) synthesized from hydrothermal carbonization of glucose were facilely modified with quaternary ammonium polyelectrolytes (QAPs) through a green and high-efficiency strategy, and they were successfully applied in anion-exchange chromatography (AEC). Methylamine and 1,4-butanediol diglycidyl ether were utilized as monomers to start the polymerization for constructing QAPs. The entire synthesis was achieved in water without damage to the monodispersity of CNSs. The water-dispersibility of CNSs was significantly increased after QAP-modification. The QAP-grafted CNSs (QAP-CNSs) were characterized by FTIR, XPS, SEM, TGA, and zeta potential measurement. The functionalization methodology was further extended to produce octadecylamine-modified CNSs, which demonstrated its versatility in preparation of functional carbons. For application in AEC, the QAP-CNSs were adhered on sulfonated poly(styrene-divinylbenzene) (PS-DVB) microspheres by electrostatic interaction. Using the PS-DVB/QAP-CNS composite as anion-exchange phase and potassium hydroxide solution as eluent, seven common anions were efficiently separated with superior stability.Keywords: carbon materials; hydrothermal carbonization; ion chromatography; polyelectrolyte; surface modification;
Co-reporter:Qiming Zhao, Shuchao Wu, Peimin Zhang, Yan Zhu
Talanta 2017 Volume 163() pp:24-30
Publication Date(Web):15 January 2017
DOI:10.1016/j.talanta.2016.10.069
•Promising application of hydrothermal carbonaceous spheres as ion chromatography stationary phase was first presented.•The ion-exchange capacity of our stationary phase could be easily tuned.•Common inorganic anions and monocarboxylic acids were well separated with good symmetrical peak shapes and stability.•Good separation performances for polarizable anions and carbohydrates were achieved.Monodisperse carbonaceous spheres produced by the hydrothermal carbonization of sucrose were first applied as green stationary phase for ion chromatography after quaternization. Depending on the polycondensation of methylamine and 1,4-butanediol diglycidyl ether, polymer containing quaternary ammonium groups were facilely grafted onto the surfaces of hydrothermal carbonaceous spheres (HCSs). The quaternized HCSs with different number of polyelectrolyte layers were characterized by scanning electron microscopy, brunauer-emmett-teller, fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis and elemental analysis. The measurements of breakthrough curves demonstrated that more layers of grafted polyelectrolyte resulted in higher anion exchange capacity of stationary phase. With good stability, common inorganic anions, monocarboxylic acids, polarizable anions and carbohydrates were effectively separated on the stationary phases, respectively. The high hydrophilicity of HCS surface afforded excellent peak symmetry for all analytes. Furthermore, high-capacity HCSs stationary phase was successfully applied to detect fluoride in tea samples.
Co-reporter:Dandan Guo, Chaoyan Lou, Peimin Zhang, Jiajie Zhang, Nani Wang, Shuchao Wu, Yan Zhu
Journal of Chromatography A 2016 Volume 1456() pp:113-122
Publication Date(Web):22 July 2016
DOI:10.1016/j.chroma.2016.05.050
•A novel anion exchange stationary phase based on PAMAM was synthesized.•Abundant surface functional groups of PAMAM result in a good ion exchange capacity.•Capacities of the PAMAM stationary phases are controllable.•Inorganic anions and carbohydrates are separated by the PAMAM stationary phases.In this work, a novel ion exchange stationary phase based on different generations of poly (amidoamine) dendrimers (PAMAM) was developed for the determination of inorganic anions and carbohydrates. Synthesis of the PAMAM was carried out with the polymerization reaction of ethylenediamine and methyl acrylate. The synthesized PAMAM was then grafted to the polystyrene-divinylbenzene-glycidyl methacrylate (PS-GMA) to form PAMAM-based beads. These beads were finally modified with 1,4-butanediol diglycidyl ether (BDDE) to generate the anion exchanger, which were characterized by scanning electron microscopy (SEM), brunauer-emmett-teller (BET), fourier transform infrared spectroscopy (FTIR), and elemental analysis. Elemental analysis, breakthrough curves and capacity factors showed that more epoxy groups and higher PAMAM generations in stationary phase could result in higher anion exchange capacity. The efficiency, durability and stability of the proposed anion exchanger were investigated by using six inorganic anions (fluoride, chloride, nitrite, bromide, nitrate and sulfate) and four carbohydrates (trehalose, glucose, maltotriose and galacturonic acid) as analytes, respectively. The reliability of the proposed ion chromatographic stationary phase was demonstrated by determining the content of galacturonic acid in polysaccharides from Poria cocos and Atractylodes macrocephala. The relative standard deviations of retention time, peak height, and peak area for galacturonic acid were 0.39%, 1.22%, and 2.02%, respectively. The spiked recoveries were in the range of 88.29%–100.51% for plant polysaccharides. Due to the good structural homogeneity, intense internal porosity, biological compatibility and high density of active groups in PAMAM, this grafted stationary phase showed good ion-exchange characteristics, especially in biological charged molecules.
Co-reporter:Wenwu Yan, Nani Wang, Peimin Zhang, Jiajie Zhang, Shuchao Wu, Yan Zhu
Journal of Chromatography A 2016 Volume 1449() pp:71-77
Publication Date(Web):3 June 2016
DOI:10.1016/j.chroma.2016.04.070
A standard-free and sensitive method was developed for analysis of sucrose acetates in a crude 6-O-acetyl sucrose (S-6-a) product by on-line hydrolysis-high-performance liquid chromatography with pulsed amperometric detection (PAD). Sucrose, three regio-isomers of acetyl sucrose and five regio-isomers of diacetyl sucrose were separated on a C18 column using 3% (v/v) acetonitrile in water as eluent within 25 min. After purification with LC followed by semi-preparative HPLC, their chemical structures were identified by 1D, 2D NMR and LC–MS. Moreover, quantification of those regio-isomers was achieved by on-line alkaline hydrolysis to liberate sucrose using a post-column delivery system, and then detected by PAD for indirect estimation of the sucrose acetate content. Under optimal conditions, the linear ranges were from 0.03 to 150 μmol L−1 for sucrose corresponding to sucrose acetates with coefficient of determination as 0.9997 and detection limit as 0.01 μmol L−1 (S/N = 3). Good repeatability was obtained (RSD < 3%, n = 6). Furthermore, this method has been successfully applied to the analysis of sucrose and sucrose acetates in a crude S-6-a product during synthesis, purification and structure elucidation studies. The recoveries were from 94.89% to 102.31% for sucrose and sucrose acetates.
Co-reporter:Wenwu Yan, Nani Wang, Peimin Zhang, Jiajie Zhang, Shuchao Wu, Yan Zhu
Food Chemistry 2016 Volume 204() pp:358-364
Publication Date(Web):1 August 2016
DOI:10.1016/j.foodchem.2016.02.099
•HPLC–ELSD was used for quantification of sucralose and ten related compounds.•Related compounds in sucralose were purified and identified by LC–MS and NMR.•Complete separation was obtained in a 14 min single run on a C18 column.•Successful application in quality control of various sucralose products was shown.•This method was more convenient and accurate than current protocols.Sucralose is widely used in food and beverages as sweetener. Current synthesis approaches typically provide sucralose products with varying levels of related chlorinated carbohydrates which can affect the taste and flavor-modifying properties of sucralose. Quantification of related compounds in sucralose is often hampered by the lack of commercially available standards. In this work, nine related compounds were purified (purity > 97%) and identified by liquid chromatography–mass spectrometry (LC–MS) and nuclear magnetic resonance (NMR), then a rapid and simple HPLC coupled with evaporative light scattering detection (ELSD) method has been developed for the simultaneous determination of sucralose and related compounds. Under optimized conditions, the method showed good linearity in the range of 2–600 μg mL−1 with determination coefficients R2 ⩾ 0.9990. Moreover, low limits of detection in the range of 0.5–2.0 μg mL−1 and good repeatability (RSD < 3%, n = 6) were obtained. Recoveries were from 96.8% to 101.2%. Finally, the method has been successfully applied to sucralose quality control and purification process monitoring.
Co-reporter:Chengzhu Ni, Binhe Zhu, Nani Wang, Muhua Wang, Suqing Chen, Jiajie Zhang, Yan Zhu
Food Chemistry 2016 Volume 194() pp:555-560
Publication Date(Web):1 March 2016
DOI:10.1016/j.foodchem.2015.08.049
•A column-switching ion chromatography method was used to analyze 8 sugars.•Organics in honeydew and nectar was removed by on-line elimination process.•Honeydew had much more oligosaccharides than nectar.•The method may be used to analyze other sugars or ions in various organic matrices.Honeydew is excreted by aphids as a sweet waste and nectar is floral honey. Honeydew and nectar are complicated samples which consist of various sugars and amino acids. In this work, a simple ion chromatography with column-switching method was developed for the simultaneous analysis of 8 monosaccharides and oligosaccharides in honeydew and nectar. A reversed-phase column was used as a pretreatment column to eliminate organics on-line and sugars were eluted from a collection loop to analytical column by using column-switching technique. This method showed good linearity (r ⩾ 0.9994) and afforded low limits of detection ranging from 1.55 to 10.17 μg L−1 for all the analytes. Recoveries ranged from 95% to 105% and repeatability results were acceptable with relative standard deviation of less than 3.21% (n = 6). This method was successfully applied to quantification of these sugars in honeydew and nectar. These results showed honeydew had much more oligosaccharides than nectar.
Co-reporter:Qiming Zhao, Shuchao Wu, Kai Zhang, Chaoyan Lou, Peiming Zhang, Yan Zhu
Journal of Chromatography A 2016 Volume 1468() pp:73-78
Publication Date(Web):14 October 2016
DOI:10.1016/j.chroma.2016.09.009
•Novel hydrothermal carbon nanospheres-based agglomerated stationary phase was prepared for ion chromatography.•Common inorganic anions were well separated on the stationary phase with good symmetrical peak shape, column efficiency and stability.•The high hydrophilicity of prepared stationary phase provided good symmetrical chromatographic peaks for polarizable anions, aliphatic monocarboxylic acids, and aromatic acids.This work reports the application of hydrothermal carbon nanospheres (HCNSs) as stationary phases in ion chromatography. HCNSs were facilely quaternized through polycondensation of methylamine and 1,4-butanediol diglycidyl ether. The quaternization was confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Owing to the electrostatic interaction, quaternized HCNSs were equably attached onto the surface of sulfonated polystyrene-divinylbenzene (PS-DVB) beads to construct the anion exchangers. The aggregation was verified by scanning electron microscopy and elemental analysis. Common anions, aliphatic monocarboxylic acids, polarizable anions, and aromatic acids were well separated on the stationary phases with good stability and symmetry. The prepared column was further applied to detect phosphate content in Cola drink samples. The limit of detection (S/N = 3) was 0.09 mg/L, and the relative standard deviation (n = 10) of retention time was 0.31%. The average recovery was 99.58%.
Co-reporter:Junwei Liu;Yong Wang;Shuchao Wu;Peimin Zhang
Journal of Separation Science 2016 Volume 39( Issue 15) pp:2970-2977
Publication Date(Web):
DOI:10.1002/jssc.201600463
In this work, poly(glycidylmethacrylate-divinylbenzene) microspheres were prepared and applied for the preparation of weak acid cation exchange stationary phases. Succinic anhydride, phthalic anhydride, and maleic anhydride were selected as carboxylation reagents to prepare three weak acid cation exchangers by direct chemical derivatization reaction without solvent or catalyst. The diameters and dispersity of the microspheres were characterized by scanning electron microscopy; the amount of accessible epoxy groups and mechanical stability were also measured. The weak acid cation exchangers were characterized by Fourier transform infrared spectroscopy; the content of carboxyl groups was measured by traditional acid base titration method. The chromatographic properties were characterized and compared by separating alkali, alkaline earth metal ions and ammonium and polar amines. The separation properties enhanced in the order of succinic anhydride, phthalic anhydride, and maleic anhydride modified poly(glycidylmethacrylate-divinylbenzene) cation exchangers.
Co-reporter:Bin-He Zhu, Cheng-Zhu Ni, Na-Ni Wang, Xun-Yan Zhao, Wei-Qiang Guo, Pei-Min Zhang, Jia-Jie Zhang, Su-Qing Chen, Wei-De Lv, Yan Zhu
Chinese Chemical Letters 2016 Volume 27(Issue 6) pp:864-866
Publication Date(Web):June 2016
DOI:10.1016/j.cclet.2016.01.037
A sensitive and accurate method based on ion chromatography was established for determination of five lithium salts in lithium-ion batteries electrolytes. Chromatographic analyses were carried out on an anion exchange column at flow rate of 1 mL/min. Under the optimal conditions, five target anions (BF4−, PF6−, TFSI−, BOB− and FSI−) exhibited satisfactory linearity with a correlation coefficient of 0.9996. The relative standard derivations of the target anions were less than less than 0.94% (n = 7). The limits of detections were in the range of 0.068–0.29 mg/L with average spiked recoveries ranging from 96.8% to 105.1%.This article describes an ion chromatography method for analysis of five lithium salts in lithium-ion battery electrolyte which has never reported by others. With a lot of work done on selection of the eluent, we finally separate the five ions which have strong retention time well.
Co-reporter:Junwei Liu, Yong Wang, Weixia Li, Peimin Zhang, Nani Wang, Shuchao Wu, Yan Zhu
Talanta 2016 Volume 160() pp:298-305
Publication Date(Web):1 November 2016
DOI:10.1016/j.talanta.2016.07.021
•Organic poly (GMA-DVB) microspheres were first applied in RPLC as supports.•The new prepared stationary phase exhibited multi-interaction mechanisms.•Eleven N-nitrosamines were better separated on the novel column than on ODS.Poly (glycidylmethacrylate-divinylbenzene) (Poly (GMA-DVB)) microspheres were prepared by the two-staged swelling and polymerization method, and modified with octadecylamine (ODA) to obtain ODA-poly (GMA-DVB) stationary phase for HPLC. The new material was characterized by scanning electron microscope, nitrogen adsorption-desorption measurement, Fourier transform infrared spectrum, elemental analysis and thermogravimetric analysis. The results showed that poly (GMA-DVB) microspheres had good monodispersity, porosity and ball shapes. The diameters and specific surface area of the microspheres were about 6 µm and 396 m2 g−1, respectively. ODA-poly (GMA-DVB) stationary phase had good thermal stability. Furthermore, the chromatographic performance of the stationary phase was illustrated by separating n-alkylbenzenes, mono-substituted benzenes and N-nitrosamines. Auxiliary quantum chemistry calculation was also carried out to evaluate the interaction mechanism. According to the evaluation, ODA-poly (GMA-DVB) stationary phase exhibited good hydrophobicity and hydrophobic selectivity, strong stereo-selectivity, polar interaction and π-π interaction. The multi-interaction mechanisms could very likely guarantee its excellent chromatographic performance for the analysis of complex samples. Finally, the column was successfully applied in the determination of N-nitrosamines in pickles sample.
Co-reporter:Junwei Liu, Yong Wang, Heli Cheng, Nani Wang, Shuchao Wu, Peimin Zhang, Yan Zhu
Talanta 2016 Volume 159() pp:272-279
Publication Date(Web):1 October 2016
DOI:10.1016/j.talanta.2016.06.034
•Poly (GMA-DVB) microspheres were prepared and applied in anion exchangers.•The exchange capacity was dependent on the content of GMA in microspheres.•Fluoride in tea sample was determined without the interference of acetate and formate.Poly (glycidylmethacrylate-divinylbenzene) microspheres were prepared by the two-staged swelling and polymerization method and applied to prepare anion exchange stationary phases. Methylamine, dimethylamine, trimethylamine, diethylamine and triethylamine were selected to prepare the quaternary ammonium groups of anion exchangers, respectively. The diameters and surface characteristics of microspheres were measured by scanning electron microscope and nitrogen adsorption-desorption measurements. The anion exchangers were characterized by Fourier transform infrared spectrum, elemental analysis and breakthrough curve methods. The chromatographic performances of anion exchangers were illustrated by separating conventional anions, organic weak acids and carbohydrates. The results indicated that the anion exchange capacities were controllable by changing either the content of glycidylmethacrylate in microspheres or the number of bonded quaternary ammonium layer. Meanwhile, the substituents of quaternary ammonium groups greatly influenced the separation properties of anion exchangers. Finally, the three-layer methylamine-quaternized anion exchanger was successfully applied for the determination of fluoride in tea sample. The content of fluoride was detected to be 0.13 mg g−1 without the interference of acetate and formate.
Co-reporter:Mu-Hua Wang, Zhong-Ping Huang, Jun-Wei Liu, Jie He, Jia-Jie Zhang, Yan Zhu
Chinese Chemical Letters 2015 Volume 26(Issue 8) pp:1026-1030
Publication Date(Web):August 2015
DOI:10.1016/j.cclet.2015.05.002
A new stationary phase for iodide ion analysis has been developed. The cationic polymer-epichlorohydrin-dimethylamine (PEPI-DMA) was served as modifier in synthesizing polyelectrolyte sorbents and the macroporous polystyrene-divinylbenzene (PS-DVB) resin was used as support. The positively charged polymer (PEPI-DMA) was electrostatically bonded to a negatively charged particle (PS-DVB sulfonated). The new stationary phase was characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), elemental analysis, chemical adsorption and desorption measurements. The chromatographic evaluation of the new stationary phase was performed using various anions with a conductivity detector. The new stationary phase was also applied to the determination of iodide directly with a DC amperometric detector using a platinum working electrode and an Ag/AgCl reference electrode. The chromatographic conditions were optimized and the eluent solution contained 5 mmol/L HNO3 and 15 mmol/L NaNO3 at a flow rate of 1.0 mL/min and column temperature of 30 °C. The applied voltage of the DC amperometric detector was 0.9 V. Under the optimum conditions, the linear range of the method was 0.2–50 mg/L for iodide ion with a correlation coefficient of 0.9990. The detection limit was 0.05 mg/L (calculated at S/N = 3) and the relative standard deviations (RSD, n = 6) were all less than 1% for retention time, peak area and peak height. This method was also utilized for the determination of iodide ions in samples of povidone iodine solution and kelp samples with satisfactory results.SEM of (A) raw styrene-divinylbenzene particle, (B) sulfonated PS-DVB particles and (C) PEPI-DMA agglomerated PS-DVB particles.
Co-reporter:Shuifeng Zhang, Liying Huang, Hongyan Li, Xiaozhen Chen, Fengli Wang, Donglei Zhang and Yan Zhu
Analytical Methods 2015 vol. 7(Issue 6) pp:2830-2838
Publication Date(Web):12 Feb 2015
DOI:10.1039/C5AY00118H
This study introduces a flexible ion chromatographic column-switching technique for the direct analysis of myo-inositol in infant formula samples by pulsed amperometric detection. The system, based on two pumps, two columns and three six-pore valves, allowed for free automatic switching between the switching time window (STW) calibration mode and analysis mode. Chromatographic parameters, including chromatographic columns, mobile phases, elution gradient, column-switching parameters, detector waveform parameters, etc., were optimized systematically for the analysis of myo-inositol in infant formula. In this method, both the pretreatment column and analytical column were arranged to be activated and regenerated during their idle time by optimizing the switching program of the three valves, thus increasing the efficiency of the method. The detection potential, E1, of the quadruple-potential waveform was also optimized and it was set to 0.027 V, which offered both excellent sensitivity and a stable baseline. By applying this optimized method to real samples, the determination of myo-inositol in infant formula was achieved in only 20 minutes, with a linear dynamic range from 0.05 μg mL−1 to 120 μg mL−1, and a limit of detection (LOD) (S/N = 3) of 2.5 μg g−1. The results demonstrate the feasibility of this method for routine analysis of myo-inositol in infant formula with the advantages of automation, simple pretreatment, low cost, good stability, and no use of organic reagents.
Co-reporter:Zhongping Huang;Chengzhu Ni;Fengli Wang;Zuoyi Zhu;Qamar Subhani;Muhua Wang
Journal of Separation Science 2014 Volume 37( Issue 3) pp:198-203
Publication Date(Web):
DOI:10.1002/jssc.201300583
The application of ion chromatography with the column-switching technique for the simultaneous analysis of peroxydisulfate and conventional inorganic anions in a single run is described. With this method, conventional inorganic anions were separated by consecutive elution through both the guard column and separation column, but peroxydisulfate that only passed through the guard column had a good peak shape and short retention time. A series of standard solutions consisting of target anions of various concentrations from 0.01 to 75 mg/L were analyzed, with a correlation coefficient (r) ≥ 0.9990. The limits of detection were in the range of 0.49–9.84 μg/L based on the S/N of 3 and a 25 μL injection volume. RSDs for retention time, peak area, and peak height were all <1.77%. A spiking study was performed with satisfactory recoveries between 97.6 and 103.4% for all anions. The quantitative determination of peroxydisulfate and conventional inorganic anions in surface waters was accomplished within 18 min by this column-switching technique.
Co-reporter:Jie He, Jia-Sheng Yu, Yan-Jie Hou, Zuo-Yi Zhu, Zhong-Ping Huang, Mu-Hua Wang, Nai-Fei Zhong, Yan Zhu
Chinese Chemical Letters 2014 Volume 25(Issue 10) pp:1392-1394
Publication Date(Web):October 2014
DOI:10.1016/j.cclet.2014.05.036
In this paper, a simple method based on ion chromatography (IC) with conductivity detection was developed for the determination of iminodiacetic acid (IDA) in the herbicide of glyphosate. Under optimized chromatographic conditions, good linear relationship, sensitivity and reproducibility were obtained. The detection limit (LOD) for IDA obtained by injecting 25 μL of sample was 31.8 μg/L (S/N = 3). Relative standard deviation (RSD) of repeated analysis for the peak areas was less than 1.53% (n = 6). A spiking study was performed with satisfactory recoveries between 92.8% and 103.6%. It was confirmed that this method could be applied in glyphosate products.A simple method based on ion chromatography (IC) with conductivity detection was developed for the determination of iminodiacetic acid (IDA) in the herbicide of glyphosate.
Co-reporter:Qamar Subhani, Zhong-Ping Huang, Zuo-Yi Zhu, Lu-Ye Liu, Yan Zhu
Chinese Chemical Letters 2014 Volume 25(Issue 3) pp:415-418
Publication Date(Web):March 2014
DOI:10.1016/j.cclet.2013.11.014
This study describes a novel application of ion chromatography coupled with post-column photochemically induced fluorimetry derivatisation in alkaline medium and fluorescence detection (IC-hv-FD) for the determination of neonicotinoid pesticide, thiacloprid. In an aqueous medium, this compound showed fluorescence with an excitation maximum at 236 nm and an emission maximum at 353 nm. The 10 mmol/L NaOH with 10% (v/v) acetonitrile solution pumped at flow rate of 1.0 mL/min was used for the chromatographic elution to isocratically separate thiacloprid on an Ion Pac® AS 11 (250 mm × 4 mm i.d; 13 μm particle size, Dionex) anion-exchange column. The linear concentration range of application was 0.04–10.0 mg/L, with a relative standard deviation (RSD, n = 7) of 1.7% (for a level of 2.0 mg/L) and detection limit (LOD, S/N = 3) of 9.9 μg/L. The procedure was applied with satisfactory results to the analysis of thiacloprid in ground and lake water samples. Pesticide average spiked recoveries ranged between 95.5% and 114.0%.A novel method was developed for the determination of thiacloprid by ion chromatography – online photochemical derivatisation – fluorescence detection. It was successfully employed for the analysis of thiacloprid in ground and lake water samples.
Co-reporter:Yang Lu, Yan Zhu
Talanta 2014 Volume 119() pp:430-434
Publication Date(Web):15 February 2014
DOI:10.1016/j.talanta.2013.11.022
•Dimethyl fumarate was successfully extracted from textiles and leathers using water as extractant.•A low cost and environment-friendly method that consumes less organic solvent.•The method provides low detection limit at the ng/g level because VALLME performances as a powerful preconcentration technique.•A novel method for determination of dimethyl fumarate in textiles and leathers.A simple and environmentally friendly sample preparation procedure coupled with gas chromatography–mass spectrometry was developed to assay dimethyl fumarate in textiles and leathers. The sample preparation procedure involved an accelerated solvent extraction (ASE) using water as the extract solvent, followed by the extraction and concentration of dimethyl fumarate from the aqueous solution using vortex-assisted liquid–liquid microextraction (VALLME). The parameters affecting the ASE and VALLME were optimized to achieve the maximum extraction efficiency, and the performance of the developed method was evaluated. Good linearity was observed over the range assayed (0.01–1 mg/kg) with a regression coefficient of 0.998. The limit of detection and enrichment factor for the VALLME step were 0.001 mg/kg and 53, respectively. The intra- and inter-day precision were below 8.9%, and the recovery was approximately 84–103%. The as-developed method was successfully applied to textiles and leather samples.
Co-reporter:Zhongping Huang, Lingling Xi, Qamar Subhani, Wenwu Yan, Weiqiang Guo, Yan Zhu
Carbon 2013 Volume 62() pp:127-134
Publication Date(Web):October 2013
DOI:10.1016/j.carbon.2013.06.004
An approach for fabrication of core–shell composite beads was described, with polystyrene–divinylbenzene (PS–DVB) as the core and multi-walled carbon nanotubes (MWCNTs) as the shell through electrostatic attraction-induced self-assembly. MWCNTs were easily quaternized with a defined number of bonded layers and desirable positive charge by a multi-step synthesis, using methylamine and 1,4-butanediol diglycidyl ether as monomers to build a branching polymer that has quaternary ammonium groups. PS–DVB beads were sulfonated by sulfuric acid to provide opposite charge, which had electrostatic interaction with quaternized MWCNTs. Functionalization of MWCNTs was characterized by techniques that include Fourier transform infrared spectroscopy, thermogravimetry and scanning electron microscopy. The dispersion of MWCNTs in deionized water was enhanced after the grafting of cationic polyelectrolytes on them, which was in agreement with the positive charge at any pH value. With the PS–DVB/MWCNT composite beads as anion exchange phase and potassium hydroxide solutions as eluent, the common inorganic anions were well separated with high stability.
Co-reporter:Zhongping Huang, Hongwei Wu, Fengli Wang, Wenwu Yan, Weiqiang Guo, Yan Zhu
Journal of Chromatography A 2013 Volume 1294() pp:152-156
Publication Date(Web):14 June 2013
DOI:10.1016/j.chroma.2013.04.045
•Cationic polyelectrolytes were introduced onto multi-walled carbon nanotubes surface.•Agglomeration between quaternized multi-walled carbon nanotubes and PS-DVB beads.•The application of multi-walled carbon nanotubes in ion chromatography.This work explores the potential of multi-walled carbon nanotubes as an agglomerated material for ion chromatography stationary phases for the separation of inorganic anions. Polyelectrolytes with quaternary ammonium groups were introduced onto the carbon nanotube surface, based on condensation polymerization of 1,4-butanediol diglycidyl ether (BDDE) and methylamine (MA). Quaternized multi-walled carbon nanotubes (Q-MWCNTs) were electrostatically adsorbed onto the surface of sulfonated polystyrene-divinylbenzene (PS-DVB) beads to generate the anion exchanger, which were confirmed by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). A 100 mm × 4.0 mm i.d. column was packed with Q-MWCNTs agglomerated PS-DVB particles, with a capacity of 56 μequiv./column. Separation of inorganic anions, such as F−, Cl−, NO2−, Br−, NO3−, SO42− and PO43− were performed. The stationary phase was rigid, chemically stable and showed good ion-exchange characteristics.
Co-reporter:Zhongping Huang, Qamar Subhani, Zuoyi Zhu, Weiqiang Guo, Yan Zhu
Food Chemistry 2013 Volume 139(1–4) pp:144-148
Publication Date(Web):15 August 2013
DOI:10.1016/j.foodchem.2013.01.070
A single pump cycling-column-switching technique has been developed for the iodate analysis in edible salt. Homemade high exchange capacity columns were adopted for the separation of iodate and chloride. Iodate could be retained and concentrated in a homemade concentrator column after eluents passing through the suppressor. With UV detection, iodate exhibited satisfactory linearity in the range of 0.1–10.0 mg/L with a correlation coefficient of 0.9996. The detection limit (LOD) was 45.53 μg/L, based on the signal-to-noise ratio of 3 (S/N = 3) and a 100 μL injection volume. Relative standard deviations (RSDs) for retention time, peak area and peak height were all less than 2.1%. Recoveries of added iodate were in the range of 98.4–101.6% for the spiked samples. The quantitative determination of iodate in edible salt was accomplished by this column-switching technique, without any pretreatment and interference. The results on six samples were statistically compared with results determined by conventional titrimetric method.Highlights► Proposal and application of a single pump cycling-column-switching technique in IC. ► Homemade columns were adopted for the separation of iodate and chloride. ► Determination of iodate in iodized edible salt without any pretreatment.
Co-reporter:Yang Lu, Yan Zhu
Journal of Chromatography A 2013 Volume 1319() pp:27-34
Publication Date(Web):6 December 2013
DOI:10.1016/j.chroma.2013.10.050
•VALLME was for the first time applied for extraction and concentration after pressurized hot water extraction.•PHWE and VALLME are simple and fast extraction procedures.•Environmental friendly method to determine chlorobenzenes in textiles.A method for quantitative determination of chlorobenzenes in textiles is developed, using pressurized hot water extraction (PHWE), vortex-assisted liquid–liquid microextraction (VALLME) and gas chromatography–mass spectrometry (GC–MS). VALLME serves as a trapping step after PHWE. The extraction conditions are investigated, as well as the quantitative features such as linearity, limits of detection (LODs), limits of quantification (LOQs), repeatabilities and reproducibilities between days. LOQs of 0.018–0.032 mg/kg were achieved. The present method provides good repeatabilities (RSD < 6.9%) and demonstrates that PHWE–VALLME–GC–MS is a simple, rapid and environmentally friendly method for determination of chlorobenzenes in textiles.
Co-reporter:Yuling Yang, Jie He, Zhongping Huang, Naifei Zhong, Zuoyi Zhu, Renyu Jiang, Jinghua You, Xiuyang Lu, Yan Zhu, Shiwei He
Journal of Chromatography A 2013 Volume 1305() pp:171-175
Publication Date(Web):30 August 2013
DOI:10.1016/j.chroma.2013.07.027
•An on-line sample pretreatment IC system is used to determine Cr(VI).•The method relies on valve-switching technique.•A polymer-based reversed-phase column is used as a pretreatment column.•The matrix in Colla corii asini can be eliminated via on-line pretreatment.An ion chromatography (IC) system with on-line sample pretreatment using valve-switching technique was developed for the determination of hexavalent chromium (Cr(VI)) in Colla corii asini. Colla corii asini is a complicated sample with organics as main matrix. In this work, a polymer-based reversed-phase column was used as a pretreatment column. Via valve-switching technique, sample solution with target ions were eluted from a collection loop to analytical columns, with matrix eliminated on-line. Under the optimized separation conditions, the method showed good linearity (r = 0.9998) in the range of 0.004–1.0 mg/L and satisfactory repeatability (RSD < 3%, n = 6). The limit of detection (LOD) was 1.4 μg/L (S/N = 3). The average spiked recoveries of Cr(VI) were 93.4–102.0%. The result showed that the on-line sample pretreatment IC system was convenient and practical for the determination of trace Cr(VI) in Colla corii asini samples
Co-reporter:Lu Yang;Wang Yiwei;Lou Caiying;Zhu Yan
Journal of Separation Science 2013 Volume 36( Issue 5) pp:947-952
Publication Date(Web):
DOI:10.1002/jssc.201200645
A dispersive liquid–liquid microextraction procedure coupled with GC-MS is described for preconcentration and determination of banned aromatic amines from textile samples. Experimental conditions affecting the microextraction procedure were optimized. A mixture of 30 μL chlorobenzene (extraction solvent) and 800 μL ACN (disperser solvent), 5 min extraction time, and 5 mL aqueous sample volume were chosen for the best extraction efficiency by the proposed procedure. Satisfactory linearity (with correlation coefficients >0.9962) and repeatability (<9.78%) were obtained for all 20 aromatic amines; detection limits attained were much lower than the standardized liquid–liquid method. The proposed method has advantages of being quicker and easier to operate, and lower consumption of organic solvent.
Co-reporter:Nani Wang;Shiwei He;Wenwu Yan
Journal of Applied Polymer Science 2013 Volume 128( Issue 1) pp:741-749
Publication Date(Web):
DOI:10.1002/app.37722
Abstract
A new monolithic stationary phase containing multiwalled carbon nanotube (MWCNT) was prepared by in situ polymerization of methacrylate monomers in a silanized capillary. The novel stationary phases were studied by scanning electron microscopy, Raman spectroscopy, thermogravimetric analysis, Fourier Transform Infrared spectroscopy, and mechanical stability test. Application of the columns in ion chromatography (IC) separation of five inorganic anions provided satisfactory under the isocratic elution condition. It was observed that MWCNT in the monoliths played an important role in the IC separation. Both the column efficiencies and exchange capacities were improved by adding MWCNT in the monoliths. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Co-reporter:Qamar Subhani, Zhongping Huang, Zuoyi Zhu, Yan Zhu
Talanta 2013 Volume 116() pp:127-132
Publication Date(Web):15 November 2013
DOI:10.1016/j.talanta.2013.05.023
•Pesticides from two different classes were separated on ion chromatographic column.•Photochemical derivatisation of pesticides was done and detected by fluorescence detector.•We successfully determined the target analytes in river, lake and ground water.A new analytical method has been developed and validated for the simultaneous determination of pesticides from different classes using ion chromatography-online photochemical derivatisation-fluorescence detector (IC-hv-FD). Fluorimetric detection was performed at λex/λem=332 nm/367 nm for imidacloprid and then detector was set at λex/λem=247 nm/470 nm for carbendazim. The two pesticides imidacloprid and carbendazim were successfully separated isocratically on an IonPac® AS11 (250 mm×4 mm i.d; 13 µm particle size, Dionex) anion-exchange column using 40 mM KOH with 10% (v/v) acetonitrile and pumped at a flow rate of 1.0 mL min−1. Under the optimized conditions, the limit of detection (LOD, S/N=3) of imidacloprid and carbendazim were 7.8 µg L−1 and 67 µg L−1, respectively. The experimental results showed that there was good linearity with a correlation coefficient (r)≥0.9966 over the range of 0.05–10 mg L−1 for imidacloprid and 0.2–15 mg L−1 for carbendazim. Good reproducibility with a relative standard deviation (RSD, n=7) less than 4.5%. Finally, the proposed method was applied with satisfactory results to the analysis of these pesticides in ground water, lake water and river water without any pre-treatment of samples. The average spiked recoveries were in the range of 90–104%.
Co-reporter:Zuoyi Zhu, Lingling Xi, Qamar Subhani, Zhongping Huang, Yan Zhu
Talanta 2013 Volume 113() pp:113-117
Publication Date(Web):15 September 2013
DOI:10.1016/j.talanta.2013.03.019
•Determination of gluconic acids by anion-exchange chromatography-pulsed amperometric detection.•Employment of the column-switching technique in AEC-PAD.•Simultaneous determination of glucose and gluconic acids within a short time.A simple ion chromatographic (IC) method for simultaneous determination of glucose, d-gluconic acid (DGA), 2-keto-d-gluconic acid (2-KDG) and 5-keto d-gluconic acid (5-KDG) was proposed, with pulsed amperometric detection (PAD) and column-switching technique. Using this technique, the four compounds were detected simultaneously in a short time with strongly retained compounds (2-KDG and 5-KDG) eluted out prior to weakly retained compounds (glucose and DGA). Under the optimized conditions, the method showed good linearity in the range of 0.01–20 mg L−1 with determination coefficients (R2)≥99.84%. Low detection limits (LODs) in the range of 0.87–2.59 μg L−1 and good repeatability (RSD<3%, n=6) were obtained. The proposed method has been successfully applied to the analysis of the four compounds in the fermentation broth, in which Gluconobacter oxydans was used to produce gluconic acids from glucose.
Co-reporter:Shuchao Wu, Wei Xu, Bingcheng Yang, Mingli Ye, Peimin Zhang, Chao Shen-Tu, Yan Zhu
Analytica Chimica Acta 2012 Volume 735() pp:62-68
Publication Date(Web):20 July 2012
DOI:10.1016/j.aca.2012.05.014
An electrolytic cell (EC), composed of two ruthenium-plated titanium electrodes separated by cation-exchange membranes, was fabricated and evaluated for online postcolumn derivatization in ion chromatography (IC). Folic acid (FA) and methotrexate (MTX) were preliminarily used as prototype analytes to test the performance of EC. After separation by an anion exchange column, FA and MTX, which emit very weak fluorescence when excited, were electrochemically oxidized online in the anode chamber of the EC. The compounds with strong fluorescence, which are oxidation products, were detected by the fluorescence detector. The phosphate buffer solution (100 mM KH2PO4) served as an optimal eluent for anion exchange chromatographic separation and a suitable supporting electrolyte for electro-oxidation, leading to ideal compatibility between IC separation and the postcolumn electrochemical derivatization. For the presently proposed method, the linear ranges were from 0.01 mg L−1 to 5 mg L−1 for both FA and MTX. The detection limits of FA and MTX were 1.8 and 2.1 μg L−1, and the relative standard deviations (RSD, n = 7) were 2.9% and 3.6%, respectively. The method was applied for the simultaneous determination of FA and MTX in the plasma of patients being treated for rheumatoid arthritis. The determination of MTX in the urine of the patients of diffuse large B cell lymphoma was also demonstrated.Graphical abstractHighlight► An electrolytic cell including ruthenium modified titanium electrode was fabricated. ► Ion chromatography/electrochemical derivatization/fluorescence detection was developed. ► Strong oxidation capacity of this EC was obtained by using the Ru/Ti electrode with large surface area.
Co-reporter:Zhongping Huang, Zuoyi Zhu, Qamar Subhani, Wenwu Yan, Weiqiang Guo, Yan Zhu
Journal of Chromatography A 2012 Volume 1251() pp:154-159
Publication Date(Web):17 August 2012
DOI:10.1016/j.chroma.2012.06.059
A simple ion chromatographic method for simultaneous detection of iodide and iodate in a single running was proposed, with columns packed with homemade functionalized polystyrene-divinylbenzene (PS-DVB) resins and column-switching technique. Homemade resins were functionalized with controllable amounts of quaternary ammonium groups. The low-capacity anion-exchange column and high-capacity anion-exchange column were prepared, due to the resins having different exchange capacities. With this method, iodide and iodate in povidone iodine solution were detected simultaneously in a short time with iodide being eluted off first. A series of standard solutions consisting of target anions of various concentrations from 0.01 mg/L to 100 mg/L were analyzed. Each anion exhibited satisfactory linearity, with correlation coefficient r ≥ 0.9990. The detection limits (LODs) for iodide and iodate obtained by injecting 100 μL of sample were 5.66 and 14.83 μg/L (S/N = 3), respectively. A spiking study was performed with satisfactory recoveries between 101.2% and 100.6% for iodide and iodate.Highlights► Controllable synthesis allowed obtaining different anion-exchange capacities. ► Application of column-switching technique in IC. ► Simultaneous determination of iodide and iodate.
Co-reporter:Ruiqi Wang, Nani Wang, Mingli Ye, Yan Zhu
Journal of Chromatography A 2012 Volume 1265() pp:186-190
Publication Date(Web):23 November 2012
DOI:10.1016/j.chroma.2012.09.086
An ion chromatographic cycling-column-switching system was developed for the determination of low-level anions (fluoride, nitrite, nitrate, bromide, sulfate, and phosphate) in seawater using a single pump, a suppressor, two valves, and three columns. Using this technique, the low-level anions were eluted from the concentrator column to the analytical columns circularly, and the matrix flowed to the waste. Under the optimized separation conditions, the method showed good linearity in the range of 0.05–25.0 mg/L and satisfactory repeatability (RSD < 4%, n = 6). The limits of detection were in the range of 2–23 μg/L (S/N = 3). The result showed that the cycling-column-switching system was convenient and practical for the determination of trace anions in high-salinity samples.Highlights► A novel ion chromatography with cycling-column-switching system was presented here. ► Only one pump was used in this system. ► Matrix interference was eliminated by cycle column-switching technology. ► Simultaneous determination of low-level ions in seawater was successfully achieved.
Co-reporter:Shuchao Wu, Bingcheng Yang, Lingling Xi, Yan Zhu
Journal of Chromatography A 2012 Volume 1229() pp:288-292
Publication Date(Web):16 March 2012
DOI:10.1016/j.chroma.2012.01.025
The current study describes the determination of phenols using ion chromatography–online electrochemical derivatization–fluorescence detection (IC/ED/FD). Six model phenols including 4-methylphenol (pMP), 2, 4-dimethylphenol (DMP), 4-tert-butylphenol (TBP), 4-hydroxylphenolacetic acid (pHPA), 4-acetamidophenol (pAAP), and phenol (P) were well separated on an anion-exchange column under ion exchange mode using NaOH with small amount of acetonitrile added as eluent. Online electrochemical derivatization performed via a laboratory-made electrolytic cell (EC), consisting of porous titanium electrode and cation-exchange membrane (CEM), allows the oxidation products that are strongly fluorescent to be detected by the fluorescence detector. NaOH eluent used in the present method matches well with the maximal fluorescence intensity obtained at alkaline condition for oxidized phenols, thus the addition of specific buffer solution after oxidation encountered in previous report could be eliminated. This process leads to a simplified procedure. The proposed method was sensitive to the limits of detection in the range of 0.4 μg/L and 3.8 μg/L and the limits of quantification between 1.2 μg/L and 13 μg/L due to the strong electro-oxidation capacity of porous titanium electrode, as well as the implementation of time-programmed potential over EC. The linear ranges were 2.0–1.0 × 104 μg/L for pAAP and DMP, and 10–1.0 × 104 μg/L for P, pMP, pHPA, and TBP, respectively. The relative standard deviations range from 0.9% to 4.8%. The utilization of the method was demonstrated by the analysis of real samples. The average spiked recoveries of target analytes in pool water were 81.0–118%.Highlights► Analysis of phenols by ion chromatography/online post-column electrochemical derivatization/fluorescence detection. ► The method was sensitive due to strong oxidation capacity of porous electrode. ► Time-programmed potential over EC enables every phenol to reach its maximum sensitivity.
Co-reporter:Hong Wei Wu, Mei Lan Chen, Dan Shou, Yan Zhu
Chinese Chemical Letters 2012 Volume 23(Issue 7) pp:839-842
Publication Date(Web):July 2012
DOI:10.1016/j.cclet.2012.04.027
A simple, fast, sensitive, highly selective and eco-friendly analytical method for the determination of catecholamines in human urine by ion chromatography (IC) with chemiluminescence (CL) detection was described in this paper. Using 12 mmol/L H2SO4 without any organic additive as eluent, three catecholamines including epinephrine (EP), norepinephrine (NE) and dopamine (DA) were well separated on a cation-exchange column. The CL detection was based on the reaction of analytes with acidic potassium permanganate in the presence of formaldehyde as an enhancer. The absence of methanol and acetonitrile in eluent made the proposed method more sensitive and eco-friendly. Under the optimal conditions, the linear range of the proposed method was in the range of 0.02–0.5 μg/mL. The limit of detection (LOD) was in the range of 0.6 and 5.1 μg/L. The relative standard deviations (RSD) for 0.1 μg/mL mixed standard solution were in the range of 0.8–1.9% (n = 11). The method has been applied to the determination of catecholamines in human urine successfully. Excellent spiked recoveries were achieved for catecholamines ranged from 91.2% to 112.7%.
Co-reporter:Hong-Wei WU, Mei-Lan CHEN, Dan SHOU, Yan ZHU
Chinese Journal of Analytical Chemistry 2012 Volume 40(Issue 11) pp:1747-1751
Publication Date(Web):November 2012
DOI:10.1016/S1872-2040(11)60588-4
A novel method was established for the simultaneous determination of resorcinol and phloroglucinol in environmental water samples by ion chromatography with chemiluminescence detection. Using 50 mM NaOH as eluent, resorcinol and phloroglucinol can be separated well with IonPac AS19 column and determined on the basis of chemiluminescence reaction of luminol and K4Fe(CN)6 in a alkaline medium. The optimal CL conditions were 6.0 × 10−4 M luminol, 0.1 M K4Fe(CN)6 and 5.5 × 10−5 M K3Fe(CN)6. The absence of methanol and acetonitrile in mobile phase made the proposed method more sensitive. Under the optimal conditions, the detection limit (LOD) of resorcinol and phloroglucinol were 4.0 and 4.3 μg L−1, respectively. The method showed good linearity within the range of 0.05-1.0 mg L−1. The relative standard deviations (RSD) for 0.1 mg L−1 resorcinol and phloroglucinol standard solutions were 0.9% and 1.1% (n = 11). The method was successfully applied to the determination of resorcinol and phloroglucinol in environmental water samples.
Co-reporter:Shuchao Wu, Wei Xu, Qamar Subhani, Bingcheng Yang, Deying Chen, Yan Zhu, Lanjuan Li
Talanta 2012 Volume 101() pp:541-545
Publication Date(Web):15 November 2012
DOI:10.1016/j.talanta.2012.09.039
This paper describes the determination of carbamazepine (CBZ) in human plasma using ion chromatography combined with online electrochemical derivatization and fluorescence detection. Separation of CBZ with anion exchange column was demonstrated to be feasible using either basic (10 mM NaOH) or acidic (0.1 M H3PO4) reagent with a small amount of acetonitrile (ACN) added as eluent. Electrochemical derivatization of CBZ into a strongly fluorescent product, which could be carried out only under the acidic condition, was investigated via the previously reported electrolytic cell (EC), as well as two modes of acidification. The linear range of CBZ for human plasma was between 10–2000 μg L−1 under the optimized experimental conditions. The limit of detection (LOD, S/N=3) was 1.3 μg L−1 and the relative standard deviation (RSD, n=7) was 2.6%. Better sensitivity and selectivity of the present method were demonstrated in comparison with ion chromatography with ultraviolet detection (IC-UV). The spiked recoveries of CBZ in 2 human plasma samples were 78.5 and 114%, respectively.Highlights► Determination of carbamazepine by ion chromatography – online electrochemical derivatization – fluorescence detection. ► Elution of carbamazepine can be performed using either basic or acidic eluent. ► Better sensitivity and selectivity were obtained compared with IC-UV.
Co-reporter:Hongwei Wu, Meilan Chen, Yunchang Fan, Fawzi Elsebaei, Yan Zhu
Talanta 2012 Volume 88() pp:222-229
Publication Date(Web):15 January 2012
DOI:10.1016/j.talanta.2011.10.036
A novel ionic liquid-based pressurized liquid extraction (IL-PLE) procedure coupled with high performance liquid chromatography (HPLC) tandem chemiluminescence (CL) detection capable of quantifying trace amounts of rutin and quercetin in four Chinese medicine plants including Flos sophorae Immaturus, Crateagus pinnatifida Bunge, Hypericum japonicum Thunb and Folium Mori was described in this paper. To avoid environmental pollution and toxicity to the operators, ionic liquids (ILs), 1-alkyl-3-methylimidazolium chloride ([Cnmim][Cl]) aqueous solutions were used in the PLE procedure as extractants replacing traditional organic solvents. In addition, chemiluminescence detection was utilized for its minimal interference from endogenous components of complex matrix. Parameters affecting extraction and analysis were carefully optimized. Compared with the conventional ultrasonic-assisted extraction (UAE) and heat-reflux extraction (HRE), the optimized method achieved the highest extraction efficiency in the shortest extraction time with the least solvent consumption. The applicability of the proposed method to real sample was confirmed. Under the optimized conditions, good reproducibility of extraction performance was obtained and good linearity was observed with correlation coefficients (r) between 0.9997 and 0.9999. The detection limits of rutin and quercetin (LOD, S/N = 3) were 1.1 × 10−2 mg/L and 3.8 × 10−3 mg/L, respectively. The average recoveries of rutin and quercetin for real samples were 93.7–105% with relative standard deviation (RSD) lower than 5.7%. To the best of our knowledge, this paper is the first contribution to utilize a combination of IL-PLE with chemiluminescence detection. And the experimental results indicated that the proposed method shows a promising prospect in extraction and determination of rutin and quercetin in medicinal plants.Highlights► The possible extraction mechanism of IL-PLE was discussed for the first time. ► The [C4mim][Cl] was more efficient than the other two ILs in the PLE. ► The high temperature and pressures of PLE were the main reasons for the high extraction efficiency. ► The selectivity of CL detector was better than UV detector when they were allowed to combine with IL-PLE. ► IL-PLE was a rapid, effective, readily automated, simple operation and environmentally friendly approach.
Co-reporter:Nani Wang;Shiwei He
European Food Research and Technology 2012 Volume 235( Issue 4) pp:685-692
Publication Date(Web):2012 October
DOI:10.1007/s00217-012-1800-1
A sensitive chromatographic method was developed for the determination of trace level bromate in food and drinking water. The method was based on a poly (glycidyl methacrylate-co-ethylene dimethacrylate) monolithic column, which was prepared by in situ polymerization and further modified with quaternary amine groups. Morphology of the stationary phases was studied by scanning electron microscopy. Permeability and mechanical stability of the column were both excellent. Bromate was detected after post-column reaction with potassium iodide at 352 nm. The parameters affecting the detection limit of bromate were studied in detail. Under the optimum conditions, the detection limit for bromate was 1.5 μg/L. This method showed good linearity over the concentration range 5.0–30 μg/L, short analysis time (8.5 min), and satisfactory relative standard deviation of the replicate analysis (n = 6, 0.043 %).
Co-reporter:Yingying Zhong, Wenfang Zhou, Haibao Zhu, Xueling Zeng, Mingli Ye, Peimin Zhang, Yan Zhu
Analytica Chimica Acta 2011 Volume 686(1–2) pp:1-8
Publication Date(Web):7 February 2011
DOI:10.1016/j.aca.2010.10.041
An ion chromatographic method with on-line sample pretreatment was developed for the trace analysis of seven common anions in concentrated matrices. The pretreatment column used in this study consisted of polystyrene-divinylbenzene (PS-DVB) and multi-walled carbon nanotubes (MWCNTs). It was too hydrophobic to retain different inorganic anions, but it showed a strong affinity for organic compounds. Thus, this chromatographic system could be used to detect trace anions in organic solvents, organic acids and relevant salts. The addition of MWCNTs decreased the surface areas of stationary phases and the retention times of organic matrices were shortened. Compared with conventional column-switching technique, only a single instrument (ICS2100) was needed in this system, including a pump, a conductivity detector, an eluent generator, a six-port valve and a ten-port valve. An electrochemical self-generating suppressor (ESGS) was adopted to convert the eluent of KOH into water for the matrix elimination. Two different eluent were employed in the chromatographic system, one for separation and the other for matrix elimination. The sample pretreatment and analysis were realized simultaneously. After optimization of this system, a calibration study was conducted by preparing and analyzing eight concentrations (between 5 and 5000 μg L−1) of mixture standards of seven anions in deionized water. The linearity was between 0.9990 and 0.9998, and the detection limits ranged from 0.41 to 3.17 μg L−1. A spiking study was performed on three representative organic chemicals with satisfactory recoveries between 88.1% and 118.5% when the concentrations of the matrices did not exceed 10 g L−1.
Co-reporter:Ying Ying Zhong, Wen Fang Zhou, Xue Ling Zeng, Ming Li Ye, Yan Zhu
Chinese Chemical Letters 2011 Volume 22(Issue 4) pp:461-464
Publication Date(Web):April 2011
DOI:10.1016/j.cclet.2010.11.011
An ion chromatography (IC) system coupled with on-line column-switching technique was used to determine anions of μg/g levels in organic chemicals of analytical reagent grade. A novel polystyrene–divinylbenzene–carbon nanotube (PS–DVB–CNT) stationary phase was utilized for matrix elimination. A calibration study was conducted by preparing and analyzing eight concentrations (between 10 and 5000 μg/L) of eight standards in deionized water. The linearity was between 0.9978 and 1. And the detection limits ranged from 1.54 μg/L to 10.02 μg/L. A spiking study was performed on two representative organic chemicals. The recoveries were between 84.3% and 119.6%.
Co-reporter:Fawzi Elsebaei, Yan Zhu
Talanta 2011 Volume 85(Issue 1) pp:123-129
Publication Date(Web):15 July 2011
DOI:10.1016/j.talanta.2011.03.037
The development of a reversed phase liquid chromatographic method for the simultaneous determination of seven angiotensin converting enzyme (ACE) inhibitors; five drugs namely benazepril HCl (BZL), enalapril maleate (ENL), fosinopril sodium (FSP), lisinopril (LSP) and ramipril (RMP) and two metabolites captopril disulfide (CPD) and enalaprilat (ENT) together with hydrochlorothiazide (HCT) is described. The method can serve as a substitute for many published papers for the analysis of the targeted compounds with or without hydrochloothiazide in pharmaceutical formulations as well as in spiked human plasma and urine samples. The method utilizes a simple gradient procedure for the separation in a 11 min run time using acetonitrile aqueous ammonia buffer (pH 9) solution and an Extend RP-C18 (25 μm particle size, 4.6 mm × 250 mm, Agilent) HPLC column. The effluent was monitored on a UV detector at 215 nm. The effect of pH, solvent strength and analysis time on the peak shape and quantification were carefully studied in order to optimize the method. Adopting the proposed procedure, the analytes produce well-shaped peaks with good linear relationship over the investigated concentration ranges. The limits of detection (LOD) and limits of quantification (LOQ) from standard drug solutions lie in the range of 17–64 and 56–212 ng mL−1, respectively. Correlation coefficient values (r) higher than 0.997 were obtained for all the studied drugs in spiked human plasma and urine samples. The intra-day and inter-day precision of the method was evaluated with relative standard deviation values being satisfactory for their purposed analysis. The method was validated with respect to specificity, recovery, accuracy, precision and linearity.
Co-reporter:Ying Ying Zhong, Wen Fang Zhou, Zhen Zhen Hu, Mei Lan Chen, Yan Zhu
Chinese Chemical Letters 2010 Volume 21(Issue 4) pp:453-456
Publication Date(Web):April 2010
DOI:10.1016/j.cclet.2009.12.032
This paper proposes the use of novel surfactant additives for the separation of organic acids by ion-pair chromatography and studies the influences of surfactants on the chromatographic separation behaviors. Researches have been carried out on both silica gel matrix and polymer supporters in order to compare the two ordinary kinds of stationary phases, and the phenomenon is similar. Separation is based on differences in the stabilities of analyte–additive complexes in solution. Retention times of analytes can be varied over a large range by varying the additive concentration. The results indicate that the additives of proper concentrations can reduce the retention times of different organic acids while the resolution remains the same. The larger the molecular weight is, the greater the shift of the retention time is. This greatly expands the scope of macromolecular polar compounds that can be separated by ion-pair chromatography with the advantages of retention times being greatly reduced.
Co-reporter:Yun-Chang FAN, She-Li ZHANG, Mei-Lan CHEN, Chao SHENTU, Yan ZHU
Chinese Journal of Analytical Chemistry 2010 Volume 38(Issue 12) pp:1785-1788
Publication Date(Web):December 2010
DOI:10.1016/S1872-2040(09)60083-9
Co-reporter:Yingying Zhong, Wenfang Zhou, Peimin Zhang, Yan Zhu
Talanta 2010 Volume 82(Issue 4) pp:1439-1447
Publication Date(Web):15 September 2010
DOI:10.1016/j.talanta.2010.07.019
A polymer-based chromatographic stationary phase with embedded or grafted multi-walled carbon nanotubes (MWCNTs) has been developed. Three different synthetic methods were utilized to combine the nano-fibers with the substrate of polystyrene–divinylbenzene (PS–DVB). After optimizing the synthetic conditions, this novel polystyrene–divinylbenzene–carbon nanotube (PS–DVB–CNT) stationary phase was characterized by scanning electron microscopy, Raman spectroscopy, thermogravimetric analysis, chemical adsorption and desorption measurement, and mechanical stability test. Compared to PS–DVB particles, PS–DVB–CNT particles have certain improvement in physical and chromatographic performances because the addition of MWCNTs has altered the structures of the particles. The novel stationary phase owns satisfactory resolution, wide pH endurance, and long lifetime, which can be used as an extent to normal HPLC.
Co-reporter:Yunchang Fan, Meilan Chen, Chao Shentu, Fawzi El-Sepai, Kaixiong Wang, Yan Zhu, Mingli Ye
Analytica Chimica Acta 2009 Volume 650(Issue 1) pp:65-69
Publication Date(Web):14 September 2009
DOI:10.1016/j.aca.2009.03.025
A simple analytical method, based on the coupling of ionic liquid-based extraction with high performance liquid chromatography (HPLC), is developed for the determination of Sudan dyes (I, II, III and IV) and Para Red in chilli powder, chilli oil and food additive samples. Two ionic liquids (ILs), 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim][PF6]) and 1-octyl-3-methylimidazolium hexafluorophosphate ([C8mim][PF6]), were compared as extraction solvents; experiments indicated that the latter possesses higher recoveries for each analyte. Parameters related to extraction of Sudan dyes and Para Red were also optimized. Under the optimal conditions, good reproducibility of extraction performance was obtained, with the relative standard deviation (RSD) values ranging from 2.0% to 3.5%. The detection limits of Sudan dyes and Para Red (LOD, S/N = 3) were in the range of 7.0–8.2 μg kg−1 for chilli powder and 11.2–13.2 μg L−1 for chilli oil and food additive. The recoveries were in the range of 76.8–109.5% for chilli powder samples and 70.7–107.8% for chilli oil and food additive samples.
Co-reporter:Xiao-min Xu, Yi-ping Ren, Yun Zhu, Zeng-xuan Cai, Jian-long Han, Bai-fen Huang, Yan Zhu
Analytica Chimica Acta 2009 Volume 650(Issue 1) pp:39-43
Publication Date(Web):14 September 2009
DOI:10.1016/j.aca.2009.04.026
A coupled capillary column system was developed for the qualitative and quantitative determination of melamine with isotope internal standard in dairy products by gas chromatography/mass spectrometry (GC/MS) without derivatization. A 30 m of DB-5ms ((5%-phenyl)-methylpolysiloxane, 0.25 mm i.d., 0.25 μm df) coupled with a 1.5 m of Innowax (polyethylene glycol, 0.32 mm i.d., 0.25 μm df) by a quartz capillary column connector was introduced as separation column. Three advantages were discussed for the coupled system. The sample was fortified with a ring-labeled 13C315N3-melamine as an isotope internal standard and extracted by 1% of trichloroacetic acid aqueous solution. 2.2% of lead acetate solution was then added to deposit protein in the sample matrix. After purification by cation exchange cartridge, the sample solution was directly injected and detected by GC/MS. A six-point calibration curve ranging from 0.05 to 2 mg kg−1 of melamine in sample was used to establish instrument response. The recovery was 93.9–102% with relative standard deviation from 3.1 to 8.7% when isotope internal standard used. The calculated method detection limit was 0.01 mg kg−1.
Co-reporter:Mei Lan Chen, Ming Li Ye, Xue Ling Zeng, Yun Chang Fan, Zhu Yan
Chinese Chemical Letters 2009 Volume 20(Issue 10) pp:1241-1244
Publication Date(Web):October 2009
DOI:10.1016/j.cclet.2009.05.003
A novel method for determination of formaldehyde sulfoxylate, sulfite, thiocyanate, and thiosulfate in foodstuffs by ion chromatography separation with postcolumn derivation and UV detection has been developed. All species are separated at Dionex IonPac AG22A and AS22A with mobile phase of a mixture of 4.5 mmol/L sodium carbonate and 0.8 mmol/L sodium bicarbonate at a flow-rate of 1.0 mL/min. The postcolumn derivation solution was 0.24% iodine in 0.2% phosphate acid and the detection wavelength was set at 288 nm. The detection limits (LOD, signal-to-noise ratio of 3) of formaldehyde sulfoxylate, sulfite, thiocyanate, and thiosulfate were 0.004, 0.006, 0.006, and 0.007 mg/L, respectively. Within-day relative standard deviations (RSD, n = 10) of formaldehyde sulfoxylate, sulfite, thiocyanate, and thiosulfate were 3.24%, 3.76%, 2.68%, and 2.07%, respectively. The recoveries of the four anions were in the range of 67.2–116.5%.
Co-reporter:Mei Lan Chen, Yun Chang Fan, Chang An Li, Dong Fei, Yan Zhu
Chinese Chemical Letters 2009 Volume 20(Issue 2) pp:207-209
Publication Date(Web):February 2009
DOI:10.1016/j.cclet.2008.10.036
In the present work, a novel analytical method was proposed for the determination of toluene diisocyanate (TDI) in synthetic-rubber track by ion chromatography (IC) coupled with an ultraviolet detector setting at 212 nm. TDI can be hydrolyzed to toluene diamine (TDA) which can be separated by cation-exchange IC easily. The optimum IC separation was performed on an IonPac CS12A column (150 mm × 4.0 mm) using 20 mmol L−1 sodium sulfate, 10 mmol L−1 sulfuric acid and 10% acetonitrile as eluent. It was found that a higher signal response of TDA could be obtained under alkaline condition. A suppressor was used to change the acidic eluent into alkaline one. 0.8 mol L−1 potassium hydroxide was chosen as the optimum regeneration eluent. With the added suppressor and regenerant, signal response was magnified by about 16 times and lower limit of detection (LOD, 0.13 μg L−1) was obtained. Within-day relative standard deviation (R.S.D.) was less than 3.6%. The recoveries of TDI spiked in synthetic-rubber track samples were 96.4–110.6%.
Co-reporter:Zhen Zhen Hu, Ying Ying Zhong, Yun Chang Fan, Yan Zhu
Chinese Chemical Letters 2009 20(12) pp: 1498-1501
Publication Date(Web):
DOI:10.1016/j.cclet.2009.07.016
Co-reporter:Chao Shen-Tu, Yunchang Fan, Yizhong Hou, Kaixiong Wang, Yan Zhu
Journal of Chromatography A 2008 Volume 1213(Issue 1) pp:56-61
Publication Date(Web):5 December 2008
DOI:10.1016/j.chroma.2008.10.016
In this work, a novel hyphenated technique ion chromatography–bianode electrochemical hydride generator–atomic fluorescence spectrometry (IC–BAECHG–AFS) system was developed for on-line simultaneous analysis of arsenite (As(III)), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), and arsenate (As(V)). Parameters that might affect hydride generation efficiency were investigated and the interference of various ions was also examined. Under the optimal conditions, the hydride generation efficiency of bianode electrochemical hydride generator (BAECHG) was close to the hydride generation efficiency of chemical hydride generator (CHG). The linear ranges were 5–200 μg L−1 for As(III), DMA and MMA and 10–200 μg L−1 for As(V). The limits of detection (LOD, S/N = 3) were 3.04, 4.27, 3.97 and 9.30 μg L−1 for As(III), DMA, MMA and As(V), respectively. The relative standard deviations (RSD, n = 7) of As(III), DMA, MMA and As(V) were 4, 3, 5 and 4%, respectively. The proposed method was also applied to the determination of the four arsenic species in dental pulp inactivative agent (type I). The recoveries of the four arsenic compounds were in the range of 91.6–103.2%.
Co-reporter:Mi-cong Jin, Xiao-hong Chen, Ming-li Ye, Yan Zhu
Journal of Chromatography A 2008 Volume 1213(Issue 1) pp:77-82
Publication Date(Web):5 December 2008
DOI:10.1016/j.chroma.2008.08.100
A novel analytical method has been developed for simultaneous determination of four indandione anticoagulant rodenticides (diphacinone, chlorophacinone, pindone and valone) in animal liver tissues by eluent generator reagent free ion chromatography coupled with electrospray ionization mass spectrometry (RFIC-ESI-MS). After the rodenticides were extracted from homogenized animal liver tissues with methanol–acetonitrile (10/90, v/v), the extracts were subjected to a solid-phase extraction (SPE) process using Oasis® HLB cartridges. The IC separation was carried out on an IonPac® AS11 analytical column (250 mm × 4.0 mm) using 10% methanol in a gradient of KOH solution at a constant flow rate of 1.0 mL/min. The objective compounds were ionized by negative ion pneumatically assisted electrospray and detected in the selected ion monitoring (SIM) mode. Warfarin was applied as an internal standard (IS) for the compensation of the losses in the course of sample processing and the sensitivity drift of the detector, linear calibration functions were calculated for all analytes. The relative average recoveries of the objective compounds spiked in animal liver tissues were between 83.4 and 104.9%. The limits of quantification (LOQs) were 0.2–1.0 ng/g for them. Within-day and day-to-day relative standard deviations (RSDs) were less than 10.4 and 13.3%, respectively. It was confirmed that this method could be used in a toxicological analysis. The coupling of IC to MS provided a new analytical tool to the analysts faced with the requirement of separating and analyzing indandione rodenticides in animal livers.
Co-reporter:Yun Chang Fan, Zheng Liang Hu, Mei Lan Chen, Chao Shen Tu, Yan Zhu
Chinese Chemical Letters 2008 Volume 19(Issue 8) pp:985-987
Publication Date(Web):August 2008
DOI:10.1016/j.cclet.2008.05.024
In this work, a new microextraction method termed ionic liquid based dispersive liquid–liquid microextraction (IL-DLLME) was demonstrated for the extraction of 2-methylaniline, 4-chloroaniline, 1-naphthylamine and 4-aminobiphenyl in aqueous matrices. After extraction the ionic liquid (IL) phase was injected directly into the high performance liquid chromatography (HPLC) system for determination. Some parameters that might affect the extraction efficiency were optimized. Under the optimum conditions, good linear relationship, sensitivity and reproducibility were obtained. The limits of detection (LOD, S/N = 3) for the four analytes were in the range of 0.45–2.6 μg L−1. The relative standard deviations (R.S.D., n = 6) were in the range of 6.2–9.8%. This method was applied for the analysis of the real water samples. The recoveries ranged from 93.4 to 106.4%. The main advantages of the method are high speed, high recovery, good repeatability and volatile organic solvent-free.
Co-reporter:Mei-Lan Chen, Wei Yan, Yongxin Chen, Zhishen Jia, Yan Zhu
Journal of Chromatography A 2007 Volume 1155(Issue 1) pp:47-49
Publication Date(Web):29 June 2007
DOI:10.1016/j.chroma.2007.02.045
In this paper, a method based on ion chromatography (IC) with conductivity detector was developed for the determination of impurities including phenyl phosphinic acid (BPA), phenyl phosphonic acid (PPOA) and crylic acid in flame retardant monomer 2-carboxyl ethyl(phenyl) phosphinic acid (CEPPA). Under favorable chromatographic conditions, good linear relationship, sensitivity and reproducibility were obtained. Detection limits of BPA, PPOA and crylic acid were 1.5, 0.5, 0.4 μg l−1, respectively. Relative standard deviations (RSD) of repeated analyses were less than 2.22% (n = 10). The real samples (white crystal) have been tested and rate of recovery were 89–108%. It was confirmed that this method could be used in the analysis of flame retardant monomers.
Co-reporter:Mi-Cong Jin, Xiao-Hong Chen, Yan Zhu
Journal of Chromatography A 2007 Volume 1155(Issue 1) pp:57-61
Publication Date(Web):29 June 2007
DOI:10.1016/j.chroma.2006.12.074
A novel analytical method is proposed for rapid simultaneous determination of five 4-hydroxycoumarin rodenticides in animal liver tissues by eluent generator reagent free ion chromatography (RFIC) with fluorescence detection. Rodenticides were initially extracted from homogenized animal liver tissues with ethyl acetate and the extracts subjected to a solid-phase extraction process using Oasis HLB cartridges. The IC separation was carried out on an IonPac® AS11 analytical column (250 mm × 4.0 mm) using gradient KOH containing 10% acetonitrile as organic modifier at a constant flow rate of 1.0 mL/min. The analytes were detected by fluorescence at an excitation wavelength of 270 nm and an emission wavelength of 380 nm. The average recoveries of the objective compounds spiked in animal liver tissues were between 81% and 98%. The limits of quantification (LOQs) were 0.004–0.010 mg/kg for them. Within-day and day-to-day relative standard deviations (RSD) were less than 8.5% and 9.7%, respectively. It was confirmed that this method could be used in a toxicological analysis.
Co-reporter:Yan-zhen Zhang;Yan-chun Zhou;Li Liu
Journal of Zhejiang University-SCIENCE B 2007 Volume 8( Issue 7) pp:507-511
Publication Date(Web):2007 June
DOI:10.1631/jzus.2007.B0507
Simple, reliable and sensitive analytical methods to determine anticariogenic agents, preservatives, and artificial sweeteners contained in commercial gargles are necessary for evaluating their effectiveness, safety, and quality. An ion chromatography (IC) method has been described to analyze simultaneously eight anions including fluoride, chloride, sulfate, phosphate, monofluorophosphate, glycerophosphate (anticariogenic agents), sorbate (a preservative), and saccharin (an artificial sweetener) in gargles. In this IC system, we applied a mobile phased gradient elution with KOH, separation by IonPac AS18 columns, and suppressed conductivity detection. Optimized analytical conditions were further evaluated for accuracy. The relative standard deviations (RSDs) of the inter-day’s retention time and peak area of all species were less than 0.938% and 8.731%, respectively, while RSDs of 5-day retention time and peak area were less than 1.265% and 8.934%, respectively. The correlation coefficients for targeted analytes ranged from 0.999 7 to 1.000 0. The spiked recoveries for the anions were 90%∼102.5%. We concluded that the method can be applied for comprehensive evaluation of commercial gargles.
Co-reporter:Yan-zhen Zhang;Zheng-yi Zhang;Yan-chun Zhou
Journal of Zhejiang University-SCIENCE B 2007 Volume 8( Issue 5) pp:302-306
Publication Date(Web):2007 April
DOI:10.1631/jzus.2007.B0302
For preparing fluorinated quinolone antibiotic medicine locally used in stomatology, simultaneous determination of norfloxacin, ciprofloxacin, and enoxacin was carried out by multiphase ion chromatography with fluorescence detection. Quinolone antibiotics were separated by Dionex OmniPac PAX-500 column with an eluent of 15 mmol/L H2SO4 and 35% methanol (v/v) at a flow-rate of 1.0 ml/min and detected with fluorescence with excitation and emission wave lengths of 347 nm and 420 nm respectively. The detection limits (S/N=3) of norfloxacin, ciprofloxacin and enoxacin were 50, 105 and 80 ng/ml respectively. The relative standard deviations of retention time, peak area and peak height were less than 1.1% and good linear relationship resulted. The developed method was applied to pharmaceutical formulations and biological fluids.
Co-reporter:Wenfang Zeng, Yongxin Chen, Hairong Cui, Feiyan Wu, Yan Zhu, James S. Fritz
Journal of Chromatography A 2006 Volume 1118(Issue 1) pp:68-72
Publication Date(Web):16 June 2006
DOI:10.1016/j.chroma.2006.01.065
A single-column method for the simultaneous determination of common cations and transition metals in real samples is proposed in this paper. Eleven cations (copper, lithium, sodium, ammonium, potassium, cobalt, nickel, magnesium, calcium, strontium and zinc) were separated and analyzed by means of ion chromatography using an isocratic elution with 2.5 mM methane sulfonic acid and 0.8 mM oxalic acid as mobile phase, IonPac SCS1 (250 mm × 4 mm I.D.) as the separation column and non-suppressed conductor detection. Optimized analytical conditions were further validated in terms of accuracy, precision and total uncertainty and the results showed the reliability of the IC method. The relative standard deviations (RSDs) of the retention time and peak area were less than 0.04 and 1.30%, respectively. The coefficients of determination for cations ranged from 0.9988 to 1.000. The method developed was successfully applied to determination of cations in samples of beer and bottled mineral water. The spiked recoveries for the cations were 94–106%. The method was applied to beer and beverage without interferences.
Co-reporter:Yongxin Chen, Mingli Ye, Hairong Cui, Feiyan Wu, Yan Zhu, James S. Fritz
Journal of Chromatography A 2006 Volume 1118(Issue 1) pp:155-159
Publication Date(Web):16 June 2006
DOI:10.1016/j.chroma.2006.01.137
Simple, reliable and sensitive analytical methods to determine the anions, such as fluoride, monofluorophaosphate, glycerophosphate related to anticaries are necessary for basic investigations of anticaries and quality control of dentifrices. A method for the simultaneous determination of organic acids, organic anions and inorganic anions in the sample of commercial toothpaste is proposed. Nine anions (fluoride, chloride, nitrite, nitrate, sulfate, phosphate, monofluorophaosphate, glycerophosphate and oxalic acid) were analyzed by means of ion chromatography using a gradient elution with KOH as mobile phase, IonPac AS18 as the separation column and suppressed conductivity detection. Optimized analytical conditions were further validated in terms of accuracy, precision and total uncertainty and the results showed the reliability of the IC method. The relative standard deviations (RSD) of the retention time and peak area of all species were less than 0.170 and 1.800%, respectively. The correlation coefficients for target analytes ranged from 0.9985 to 0.9996. The detection limit (signal to noise ratio of 3:1) of this method was at low ppb level (<15 ppb). The spiked recoveries for the anions were 96–103%. The method was applied to toothpaste without interferences.
Co-reporter:Micong Jin, Yan Zhu
Journal of Chromatography A 2006 Volume 1118(Issue 1) pp:111-117
Publication Date(Web):16 June 2006
DOI:10.1016/j.chroma.2006.03.063
A novel analytical method has been developed for the determination of 14 trace chlorophenols in clam tissues by ion chromatography (IC) coupled with atmospheric pressure chemical ionization mass spectrometry (APCI-MS) in the negative mode. The method comprised a fast ultrasound-assisted extraction using a mixture of methanol/water (4:1 v/v) containing 5% triethylamine (TEA) as extraction solvent, solid-phase extraction with an Oasis HLB cartridge and gradient separation using KOH/acetonitrile at a flow rate of 1.0 mL/min on an IonPac AG11 guard column (50 mm × 4.0 mm I.D.) and an IonPac AS11 analytical column (250 mm × 4.0 mm I.D.). The molecular ions m/z [M − H]− 127, 129; 161, 163; 195, 197 and 263, 265, 267 were selected for quantification in the selected ion monitoring (SIM) mode for monochlorophenols (MCPs), dichlorophenols (DCPs), trichlorophenols (TCPs) and pentachlorophenol (PCP), respectively. The average recoveries of the objective compounds spiked in clam tissues were between 80.2% and 98.2%. Within-day and day-to-day relative standard deviations were less than 12.6% and 13.2%, respectively. The optimum IC-APCI-MS conditions were successfully applied to the analyses of 14 trace chlorophenols in clam tissues.
Co-reporter:Lingling Xi, Genfu Wu, Yan Zhu
Journal of Chromatography A 2006 Volume 1115(1–2) pp:202-207
Publication Date(Web):19 May 2006
DOI:10.1016/j.chroma.2006.02.093
A new method for determination of etimicin's (ETM) purity and content is developed by liquid chromatography (LC) and pulsed amperometric detection (PAD). A reversed-phase ion-pair LC method with pulsed amperometric detection on a gold electrode after post-added NaOH is described. The mobile phase consisted of an aqueous solution containing 0.033 mol L−1 oxalic acid, 0.012 mol L−1 heptafluorobutyric acid, and 210 mL L−1 acetonitrile with pH 3.40 adjusting by dilute NaOH solution. The total analysis time was not more than 30 min. The effects of the different chromatographic parameters on the separation were also investigated. A number of commercial samples of etimicin sulfate were analyzed using this method.
Co-reporter:Yan Zhu, Chen Yongxin, Ye Mingli, James S. Fritz
Journal of Chromatography A 2005 Volume 1085(Issue 1) pp:18-22
Publication Date(Web):26 August 2005
DOI:10.1016/j.chroma.2005.03.053
New technology is reported here for the synthesis of an effective weak acid–cation exchanger for ion chromatography. Monodisperse macroporous poly(ethylvinylbenzene-co-divinylbezene) (PEVB–DVB) beads of 5 μm diameter were prepared by a two-step swelling and polymerization method. Then carboxyl groups were introduced by polymerization of maleic anhydride with unreacted vinyl groups on the resin beads, followed by hydrolysis of the maleic anhydride groups. A column packed with the carboxylate beads was used to separate alkali and alkaline earth metal ions in a single isocratic run. Separations were found to be better than those with similar resin particles that are simply coated with maleic acid. The columns containing the new particles were 100% compatible with solvents commonly used for HPLC. Additionally, the prepared column was stable and could be used for a long time in a wide range of pH. The column gave good resolution, low detection limits and good repeatability for the separation of common cations. Satisfactory results were also obtained for separations of organic amines and of common cations in rainwater.
Co-reporter:Yan Zhu, Yingying Guo, Mingli Ye, Frits S. James
Journal of Chromatography A 2005 Volume 1085(Issue 1) pp:143-146
Publication Date(Web):26 August 2005
DOI:10.1016/j.chroma.2004.12.042
In this paper, the separation and determination of four artificial sweeteners (aspartame, sodium cyclamate, acesulfame-K and sodium saccharin) by ion chromatography coupled with suppressed conductivity detector is reported. The four artificial sweeteners were separated using KOH eluent generator. Due to the use of eluent generator, very low conductance background conductivity can be obtained and sensitivity of sweeteners has been greatly improved. Under the experimental condition, several inorganic anions, such as F−, Cl−, NO3−, NO2−, Br−, SO42−, PO43− and some organic acid such as formate, acetate, benzoate, and citrate did not interfere with the determination. With this method, good linear relationship, sensitivity and reproducibility were obtained. Detection limits of aspartame, sodium cyclamate, acesulfame-K, sodium saccharin were 0.87, 0.032, 0.019, 0.045 mg/L, respectively. Rate of recovery were between 98.23 and 105.42%, 99.48 and 103.57%, 97.96 and 103.23%, 98.46 and 102.40%, respectively. The method has successfully applied to the determination of the four sweeteners in drinks and preserved fruits.
![2-[2,5-BIS(CHLOROMETHYL)-3,4-DIHYDROXYOXOLAN-2-YL]OXY-6-(CHLOROMETHYL)OXANE-3,4,5-TRIOL](http://img.cochemist.com/ccimg/40700/40631-75-2.png)
![2-[2,5-BIS(CHLOROMETHYL)-3,4-DIHYDROXYOXOLAN-2-YL]OXY-6-(CHLOROMETHYL)OXANE-3,4,5-TRIOL](http://img.cochemist.com/ccimg/40700/40631-75-2_b.png)
