Li-ming Du *

Extraction of quinolones from milk samples using bentonite/magnetite nanoparticles before determination by high-performance liquid chromatography with fluorimetric detection

Co-reporter:Tao Jin;Hao Wu;Nannan Gao;Xiaodan Chen;Huajie Lai;Jinfeng Zheng;Liming Du

Journal of Separation Science 2016 Volume 39( Issue 3) pp:545-551

Publication Date(Web):

DOI:10.1002/jssc.201500856

In this work, bentonite magnetic nanoparticles synthesized by a typical coprecipitation method were used as the adsorbent for the magnetic solid-phase extraction of six quinolones (ciprofloxacin, difloxacin, enrofloxacin, norfloxacin, sarafloxacin, and lomefloxacin) from milk samples followed by high-performance liquid chromatography with fluorimetric detection. Under the optimized conditions, the linear quantitation range for the six quinolones was 0.3–200 ng/mL, and the correlation coefficients of the calibration curves ranged from 0.9994 to 0.9999. The detection limit of the method was 0.1 ng/mL. Recoveries of quinolones from pure and low-fat spiked milk samples varied from 80.4 to 92.7% and from 81.3 to 93.5%, respectively. These results demonstrated that the proposed method for the determination of six quinolones in milk samples was rapid, reliable, and efficient.

Mixed hemi/ad-micelle SDS-coated magnetic Fe2−xAlxO3 (x = 0.4) nanoparticles for the capture of gatifloxacin and prulifloxacin coupled with fluorimetric determination

Co-reporter:Juanli Du, Hao Wu, Yu An, Yating Shi, Xiaozhen Guo and Liming Du

Analytical Methods 2016 vol. 8(Issue 13) pp:2778-2785

Publication Date(Web):03 Mar 2016

DOI:10.1039/C5AY03285G

A new method was developed for the isolation and preconcentration of gatifloxacin (GTFX) and prulifloxacin (PUFX) based on magnetic mixed hemimicelle solid-phase extraction (MMHSPE) using sodium dodecyl sulphate (SDS) coated Fe2−xAlxO3 (x = 0.4) MNPs as the sorbent. The Fe2−xAlxO3 MNPs not only prevent dissolution of the Fe3O4 MNPs in acidic solutions but also extend their application without sacrificing their unique magnetic characteristics. Due to the high surface area of these new sorbents and the excellent adsorption capacity after surface modification by SDS, satisfactory preconcentration factors and extraction recoveries were produced with only 8 mg of Fe2−xAlxO3 MNPs. It is important to note that the largest adsorption capacity of the as-synthesized Fe2−xAlxO3 nanoparticles occurs at x = 0.4. Several parameters that affected the extraction efficiency were investigated, including the type and volume of desorption solvent, extraction and desorption time, pH of the solution, addition of NaCl and the sorbent amount. Under the optimized extraction conditions, a linear response was observed in a concentration range of 0.4 to 120 ng mL−1 for GTFX and 2 to 240 ng mL−1 for PUFX, and the limits of detection were 0.030 and 0.070 ng mL−1, respectively. The proposed procedure was applied successfully for the detection of the investigated drugs in their pharmaceutical dosage forms, plasma and urine.

Automated Magnetic Solid-Phase Extraction for Synthetic Food Colorant Determination

Co-reporter:Hao Wu;Nannan Gao;Lizhen Zhang;Yunrong Li;Yating Shi

Food Analytical Methods 2016 Volume 9( Issue 3) pp:614-623

Publication Date(Web):2016 March

DOI:10.1007/s12161-015-0219-2

A new automated magnetic solid-phase extraction (MSPE) method was developed and combined with high-performance liquid chromatography (HPLC) and spectrophotometry for off-line and on-line quantitative enrichment and determination of synthetic food colorants in food samples. Fe3O4-poly (ionic liquid) core-shell microspheres were prepared as a sorbent to quickly extract analytes from aqueous samples. The entire MSPE process, including extraction, separation, elution, and cleaning, was automated using common equipment. The main parameters affecting the performance of MSPE and the automated process, such as absorbent, sample pH, eluent, flow rate, elution time, etc., were investigated in detail. Under the optimum experimental conditions, the limits of detection ranged between 4.1 and 14 ng/mL by off-line HPLC and were 220 ng/mL for the determination of amaranth by on-line spectrophotometry, with excellent reproducibility (intra- and inter-day relative standard deviations were less than 3.2 %). The developed method was successfully applied to the determination of colorants in food samples.

Microwave-assisted decomposition coupled with acidic food condiment as an efficient technology for ginger (Zingiber officinale Roscoe) processing

Co-reporter:Jing-bo Guo, Wen-jie Zhang, Hao Wu, Li-ming Du

Separation and Purification Technology 2015 Volume 146() pp:219-226

Publication Date(Web):26 May 2015

DOI:10.1016/j.seppur.2015.03.049

•The microwave-assisted process provides highly efficient conversion.•Tartaric acid is the best catalyst for the conversion of gingerols into shogaols.•This method gains higher shogaols contents than previously reported techniques.Shogaols are the dehydration products of gingerols that are found in small quantities in ginger root and have more potent bioactive properties than gingerols. In this study, microwave-assisted technology coupled with acidic food condiments was used to improve the contents of 6-, 8-, and 10-shogaols. After processing ginger in aqueous tartaric acid solution (0.8 mol/L, 8 mL) at 140 °C and 1000 W for 10 min, the contents of 6-, 8-, and 10-shogaols (4.66, 1.19, and 1.76 mg/g dry mass, respectively) were approximately 12-, 17-, and 19-fold higher in processed ginger than in unprocessed ginger. The antioxidant capabilities of this processed ginger were approximately two times higher than those of unprocessed ginger assayed by antioxidant assays. The processed gingers can be used as high-quality raw materials for the production of various ginger products, as well as for the preparative separation and purification of 6-, 8-, and 10-shogaols.

Ionic Liquid-Magnetic Nanoparticle Microextraction of Safranin T in Food Samples

Co-reporter:Lizhen Zhang;Hao Wu;Zhenzhen Liu;Nannan Gao;Liming Du

Food Analytical Methods 2015 Volume 8( Issue 3) pp:541-548

Publication Date(Web):2015 March

DOI:10.1007/s12161-014-9927-2

A new two-step microextraction approach combining ionic liquid-dispersive liquid–liquid microextraction with magnetic-dispersive microsolid-phase extraction was developed for the fluorescence determination of safranin T in food samples. In the first step, ionic liquid (1-hexyl-3-methylimidazolium hexafluorophosphate (C6MIM][PF6)) was used to extract safranin T from a sample solution with the assistance of controlled temperature conditions. Fe3O4@SiO2 magnetic nanoparticles were then used to retrieve the ionic liquid, which were collected by application of an external magnetic field. The ionic liquid and safranin T were recovered from the surface of magnetic nanoparticles using ultrasound and an organic solvent. The effective factors in the proposed method, including type and volume of extraction solvent, pH, dispersive temperature and extraction time, type of desorption solvent, amount of Fe3O4@SiO2 magnetic nanoparticles, and ultrasound time were optimized. Under the optimal conditions (extraction solvent, 100 μL of [C6MIM][PF6]; pH 9.0; dispersive temperature, 80 °C; extraction time, 5 min; desorption solvent, acetone; amount of Fe3O4@SiO2 magnetic nanoparticles, 5 mg; ultrasound time, 120 s), the method presented has good linearity (r2 = 0.9994) in the range of 5–300 ng mL−1. The detection limit was 0.48 ng mL−1, while the relative standard deviation for the analysis of 100 ng mL−1 of the safranin T was 1.47 % (n = 10). The method was successfully applied to the determination of safranin T in tomatoes, tomato sauce, and yuba samples, and good recovery rates (96.71–98.26 %) with relative standard deviation of below 2 % were achieved.

A competitive strategy based on cucurbit[7]uril supramolecular interaction for simple and sensitive detection of dibucaine

Co-reporter:Yan Li, Chang-Feng Li, Li-Ming Du, Jian-Xia Feng, Hai-Long Liu, Yun-Long Fu

Talanta 2015 Volume 132() pp:653-657

Publication Date(Web):15 January 2015

DOI:10.1016/j.talanta.2014.09.005

•The fluorescence method was used for determination of dibucaine for the first time.•The competitive strategy was designed for determination of dibucaine.•The occupancy of the cucurbit[7]uril cavity was studied by spectroscopy and calculations.•The proposed method showed good sensitivity for detection of dibucaine in biological fluids.In this work, the competitive interaction between dibucaine and three fluorescent probes (i.e., berberine, palmatine, and coptisine) for occupancy of the cucurbit[7]uril (CB[7]) cavity was studied by fluorescence spectra, UV–visible absorption spectra, 1H NMR spectra, and theoretical calculations in acidic aqueous solution. Based on the fluorescence enhancement of berberine, palmatine, and coptisine upon binding with CB[7], respectively, a series of fluorescence detection methods for dibucaine were proposed. At the optimized conditions, the fluorescence intensity of berberine-CB[7], palmatine-CB[7], and coptisine-CB[7] complexes showed negative correlation to the concentration of dibucaine, which led to a series of simple and sensitive fluorescence methods for the determination of dibucaine for the first time. Linear ranges obtained in the detection of the dibucaine were 0.018–3.34 μmol L−1, 0.032–4.47 μmol L−1, and 0.079–4.42 μmol L−1 with detection limits of 6.0 nmol L−1, 12.0 nmol L−1, and 25.0 nmol L−1, respectively. Moreover, the proposed method was successfully applied for the determination of the drug in biological fluids. The competitive mode based on CB[7] superstructure provided a promising assay strategy for fluorescence detection in various potential applications.The competitive interaction between dibucaine (DC) and three fluorescent probes (i.e., berberine (BER), palmatine (PAL), and coptisine (COP)) for occupancy of the cucurbit[7]uril (CB[7]) cavity was observed and used for simple and sensitive detection of dibucaine.

Mixed micelle cloud point-magnetic dispersive μ-solid phase extraction of doxazosin and alfuzosin

Co-reporter:Nannan Gao, Hao Wu, Yafen Chang, Xiaozhen Guo, Lizhen Zhang, Liming Du, Yunlong Fu

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 2015 Volume 134() pp:10-16

Publication Date(Web):5 January 2015

DOI:10.1016/j.saa.2014.06.095

•Mixed micelle cloud point extraction combined with magnetic dispersive μ-solid phase extraction.•The method significant simplification to conventional MM-CPE procedures.•The limits of detection were 0.21 and 0.16 ng mL−1 for DOX and ALF, respectively.•Successfully applied for the determination of the drugs in tablets, urine, and plasma.Mixed micelle cloud point extraction (MM-CPE) combined with magnetic dispersive μ-solid phase extraction (MD-μ-SPE) has been developed as a new approach for the extraction of doxazosin (DOX) and alfuzosin (ALF) prior to fluorescence analysis. The mixed micelle anionic surfactant sodium dodecyl sulfate and non-ionic polyoxyethylene(7.5)nonylphenylether was used as the extraction solvent in MM-CPE, and diatomite bonding Fe3O4 magnetic nanoparticles were used as the adsorbent in MD-μ-SPE. The method was based on MM-CPE of DOX and ALF in the surfactant-rich phase. Magnetic materials were used to retrieve the surfactant-rich phase, which easily separated from the aqueous phase under magnetic field. At optimum conditions, a linear relationship between DOX and ALF was obtained in the range of 5–300 ng mL−1, and the limits of detection were 0.21 and 0.16 ng mL−1, respectively. The proposed method was successfully applied for the determination of the drugs in pharmaceutical preparations, urine samples, and plasma samples.Graphical abstract

Anionic Surfactant Micelle-Mediated Extraction Coupled with Dispersive Magnetic Microextraction for the Determination of Phthalate Esters

Co-reporter:Hao Wu, Hong Tian, Ming-Fei Chen, Jun-Chen You, Li-Ming Du, and Yun-Long Fu

Journal of Agricultural and Food Chemistry 2014 Volume 62(Issue 31) pp:7682-7689

Publication Date(Web):July 16, 2014

DOI:10.1021/jf502364x

A novel and easy two-step microextraction technique combining anionic surfactant coacervation phase (CAP) extraction and dispersive microsolid-phase extraction (D-μ-SPE) was developed for the high-performance liquid chromatography–ultraviolet detection to determination of phthalate esters (PEs) in water samples. The method started with the phase separation of sodium dodecylbenzenesulfonic acid (SDBSA) obtained by adding NaCl, whereas the target analytes were extracted in the CAP. The CAP was then retrieved using diatomaceous earth-supported magnetite nanoparticles. The effects of solution acidity, SDBSA, and electrolyte concentration, extraction time, magnetic material quantity, and elution solvent volume were discussed. Under optimal extraction conditions, the extraction recoveries ranged from 48.6 to 84.8%, and relative standard deviations ranged from 3.9 to 5.7% (n = 10). The detection limits ranged from 0.5 to 5.0 ng mL–1 for the five PEs. The proposed method was used to determine the five PEs in the water samples and recoveries between 85.7 and 105.5%.

Anionic surfactant coacervation extraction-magnetic solid phase microextraction for determination of malachite green

Co-reporter:Hong Tian, Hao Wu, Chengxuan Hao, Liming Du and Yunlong Fu

Analytical Methods 2014 vol. 6(Issue 19) pp:7703-7709

Publication Date(Web):22 Jul 2014

DOI:10.1039/C4AY01144A

A novel, fast, and efficient two-step microextraction technique for preconcentration and extraction of trace amounts of malachite green in fishpond water, river water and flesh of fish was developed using spectrophotometry. MG with a pH of 6.5 was extracted and mediated by the coacervation phase of the anionic surfactant sodium dodecyl benzene sulfonate. The coacervation phase was then trapped by diatomite bonded Fe3O4 magnetic nanoparticles (DBMNPs) that can rapidly achieve two-phase separation in a magnetic field. The extracted surfactant-rich phase was diluted with ethanol and its absorbance was measured at 624 nm. A number of important parameters affecting extraction efficiency, such as the volume of extraction solvent, amount of salt, pH, amount of DBMNPs, equilibration temperature and time, were investigated. The calibration graph was linear for MG ranging from 2 ng mL−1 to 180 ng mL−1 in the initial solution, with r2 = 0.9994 (n = 10). The detection limit based on three times the standard deviation of the blank (3Sb) was 0.67 ng mL−1 and the relative standard deviation for 20 ng mL−1 of MG was 1.12% (n = 5). The method was applied to determine the trace amounts of MG from fishpond water, river water and flesh of fish.

Supramolecular Interaction of Two Tryptophans with p-sulfonated calix[4,6,8]arene

Co-reporter:Tao-Tao Pang;Hai-Long Liu;Li-Ming Du;Yin-Xia Chang

Journal of Fluorescence 2014 Volume 24( Issue 1) pp:143-152

Publication Date(Web):2014 January

DOI:10.1007/s10895-013-1280-0

The complex characteristics of p-sulfonated calix[n]arene (SCnA) and two tryptophans N-[(tert-butoxy) carbonyl]-tryptophan (trp-A) and N-carbobenzoxy-tryptophane (trp-B) were examined through various techniques. Spectrofluorimetry was performed at different temperatures to determine the stability constants and evaluate the thermodynamic parameters of the two complexes. The effect of pH on complex formation was estimated. According to the fluorescence data, the assumption about the steric hindrance of the tert-butyl group of trp-A and the phenyl group of trp-B was put forward. 1H NMR was also performed to determine the binding interaction mechanism. Results showed that the indole benzene rings of the two tryptophans partly penetrated into the cavity of p-sulfonated calix[n]arene. The shift in Ha, Hb and Hc, Hd positions became more significant as the number of phenolic units of the calixarene ring increased. Molecular modeling of the complexes elucidated the assumption about the steric hindrance of the tert-butyl group of trp-A and the phenyl group of trp-B. These observations of molecular modeling computation are consistent with previous fluorescence data and 1H NMR results.

A rapid shaking-based ionic liquid dispersive liquid phase microextraction for the simultaneous determination of six synthetic food colourants in soft drinks, sugar- and gelatin-based confectionery by high-performance liquid chromatography

Co-reporter:Hao Wu, Jing-bo Guo, Li-ming Du, Hong Tian, Cheng-xuan Hao, Zhi-feng Wang, Jie-yan Wang

Food Chemistry 2013 Volume 141(Issue 1) pp:182-186

Publication Date(Web):1 November 2013

DOI:10.1016/j.foodchem.2013.03.015

•Rapid shaking-based ionic liquid dispersive liquid phase microextraction was established.•[C8MIM][BF4] was dispersed in an aqueous solution as fine droplets by rapid shaking.•[C8MIM][BF4] have the best extraction efficiency for the colourants compared to commonly used ILs.•The limits of detection with in 0.015–0.32 ng/mL.•This is the first report of IL extraction synthetic food colourants.A novel and simple rapid shaking-based method of ionic liquid dispersive liquid phase microextraction for the determination of six synthetic food colourants (Tartrazine, Amaranth, Sunset Yellow, Allura Red, Ponceau 4R, and Erythrosine) in soft drinks, sugar- and gelatin-based confectionery was established. High-performance liquid chromatography coupled with an ultraviolet detector was used for the determinations. The extraction procedure did not require a dispersive solvent, heat, ultrasonication, or additional chemical reagents. 1-Octyl-3-methylimidazolium tetrafluoroborate ([C8MIM][BF4]) was dispersed in an aqueous sample solution as fine droplets by manual shaking, enabling the easier migration of analytes into the ionic liquid phase. Factors such as the [C8MIM][BF4] volume, sample pH, extraction time, and centrifugation time were investigated. Under the optimum experimental conditions, the proposed method showed excellent detection sensitivity with limits of detection (signal-to-noise ratio = 3) within 0.015–0.32 ng/mL. The method was also successfully used in analysing real food samples. Good spiked recoveries from 95.8%–104.5% were obtained.

Study on the supramolecular interaction of astemizole with cucurbit[7]uril and its analytical application

Co-reporter:Guang-Quan Wang, Li-Ming Du, Yu-Hua Guo, Yan-Fang Qin, Jun-Wen Wang and Hao Wu

Analytical Methods 2013 vol. 5(Issue 1) pp:173-179

Publication Date(Web):06 Nov 2012

DOI:10.1039/C2AY25929J

Astemizole (AST) is non-fluorescent in aqueous solution. This property makes its determination through direct fluorescence methods difficult. Reaction and supramolecular interaction mechanisms, between AST and palmatine (PAL) as they compete for occupancy of the cucurbit[7]uril (CB[7]) cavity, were studied using spectrofluorimetry, 1H NMR, and molecular modeling calculations. The association constants of the complexes formed between the host and the guest were determined. Based on the significant quenching of the supramolecular complex fluorescence intensity, a fluorescent probe method of high sensitivity and selectivity was developed to determine AST in its pharmaceutical dosage forms and in urine samples with good precision and accuracy. The linear range of the method was from 0.02 μg mL−1 to 2.2 μg mL−1. The detection limit was 0.007 μg mL−1. This shows that the proposed method has promising potential for therapeutic monitoring and pharmacokinetics and for clinical application.

Determination of Brilliant Blue FCF in food and cosmetic samples by ionic liquid independent disperse liquid–liquid micro-extraction

Co-reporter:Jingbo Guo, Hao Wu, Liming Du and Yunlong Fu

Analytical Methods 2013 vol. 5(Issue 16) pp:4021-4026

Publication Date(Web):05 Jun 2013

DOI:10.1039/C3AY40362A

A novel, relatively fast and simple method of ionic liquid independent disperse liquid–liquid micro-extraction (IL-IDLLME) coupled with UV-Visible spectroscopy was developed and applied to determination of the synthetic dye Brilliant Blue FCF (E133) in six different kinds of food and cosmetic samples, namely soft drinks, candy, jelly, kiwi fruit (Actinidia chinensis) pieces, roasted pea, ice cream, eau de toilette and shampoo. The samples were dissolved in water and preconcentrated simply by using 1-decyl-3-methylimidazolium tetrafluoroborate ([C10MIM][BF4]) without a dispersive solvent, heat, ultrasonication or additional chemical reagents. The effects of different parameters such as the volume of [C10MIM][BF4], pH, KCl concentration, micro-extraction temperature, incubation time and centrifugation time on the micro-extraction of E133 (0.12 μg mL−1) were investigated and optimum conditions were established. A linear calibration curve was obtained in the range of 1.5–150 μg L−1 for E133 under optimum conditions. The limit of detection (LOD) based on 3Sb was 0.34 μg L−1 (n = 11). The relative standard deviation (R.S.D.) for 5 and 140 μg L−1 of E133 was 0.43% and 0.82% (n = 10), respectively. The method is therefore recommended for use by the quality control departments of food and cosmetic producers using E133.

Spectrofluorometry determination of chelerythrine by TAIL-DLPME: ionic liquid serves as both extractant and solvent

Co-reporter:Li-bing Zhang, Hao Wu, Li-ming Du, Guang-quan Wang and Yin-xia Chang

Analytical Methods 2012 vol. 4(Issue 4) pp:1117-1121

Publication Date(Web):14 Mar 2012

DOI:10.1039/C2AY00008C

In the present study, a new ionic liquid extraction method was developed for the sensitive and accurate determination of chelerythrine in an aqueous solution. The results show that chelerythrine fluorescence increases significantly in ionic liquids, with 1-hexyl-3-methy-limidazolium hexafluorophosphate ([C6MIM][PF6]) having the greatest increase. Based on the significant enhancement of extraction efficiency of chelerythrine in ionic liquids, a sensitive spectrofluorometry method for the quantitative estimation of chelerythrine was established. At optimum conditions, a linear relationship was obtained in the range of 0.2–130 ng mL−1. The detection limit was 0.059 ng mL−1. The enrichment factor was 81.7, and the extraction recovery for chelerythrine was 98.1%. The proposed method was successfully applied for the determination of the chelerythrine in urine and serum samples.

Determination of amantadine and rimantadine using a sensitive fluorescent probe

Co-reporter:Guang-Quan Wang, Yan-Fang Qin, Li-Ming Du, Jun-Fei Li, Xu Jing, Yin-Xia Chang, Hao Wu

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 2012 Volume 98() pp:275-281

Publication Date(Web):December 2012

DOI:10.1016/j.saa.2012.08.016

Amantadine hydrochloride (AMA) and rimantadine hydrochloride (RIM) are non-fluorescent in aqueous solutions. This property makes their determination through direct fluorescent method difficult. The competing reactions and the supramolecular interaction mechanisms between the two drugs and coptisine (COP) as they fight for occupancy of the cucurbit[7]uril (CB[7]) cavity, were studied using spectrofluorimetry, 1H NMR, and molecular modeling calculations. Based on the significant quenching of the supramolecular complex fluorescence intensity, a fluorescent probe method of high sensitivity and selectivity was developed to determine AMA or RIM in their pharmaceutical dosage forms and in urine samples with good precision and accuracy. The linear range of the method was from 0.0040 to 1.0 μg mL−1 with a detection limit ranging from 0.0012 to 0.0013 μg mL−1. This shows that the proposed method has promising potential for therapeutic monitoring and pharmacokinetics and for clinical application.Graphical abstractHighlights► The analysis method is novel. ► A novel fluorescent probe method was used to determine the analyte. ► The method had higher sensitivity than all of reported analysis methods for amantadine and rimantadine. ► The interaction models of the complexes was established through theoretical calculations. ► The mechanisms of the competing reactions were studied using 1H NMR.

Determination of ranitidine, nizatidine, and cimetidine by a sensitive fluorescent probe

Co-reporter:Yin-Xia Chang, Yue-Qin Qiu, Li-Ming Du, Chang-Feng Li and Min Guo

Analyst 2011 vol. 136(Issue 20) pp:4168-4173

Publication Date(Web):22 Aug 2011

DOI:10.1039/C1AN15078B

A validated, simple, and sensitive fluorescence quenching method for the determination of ranitidine, nizatidine, and cimetidine in tablets and biological fluids is presented. This is the first single fluorescence method reported for the analysis of all three H2 antagonists. The competitive reaction between the investigated drug and the palmatine probe for the occupancy of the cucurbit[7]uril (CB[7]) cavity was studied using spectrofluorometry. CB[7] was found to react with the probe to form a stable complex. The fluorescence intensity of the complex was also enhanced greatly. However, the addition of the drug dramatically quenched the fluorescence intensity of the complex. Accordingly, a new fluorescence quenching method for the determination of the studied drugs was established. The different experimental parameters affecting the fluorescence quenching intensity were studied carefully. At optimum reaction conditions, the rectilinear calibration graphs between the fluorescence quenching values (ΔF) and the medicament concentration were obtained in the concentration range of 0.04–1.9 μg mL−1 for the investigated drugs. The limits of detection ranged from 0.013 to 0.030 μg mL−1 at 495 nm using an excitation wavelength of 343 nm. The proposed method can be used for the determination of the three H2 antagonists in raw materials, dosage forms and biological fluids.

Determination of L-Cystine by a New Sensitive Cucurbit[7]uril/palmatine Probe

Co-reporter:Jiyuan Yang;Liming Du;Hao Wu;Yinxia Chang ;Changfeng Li

Chinese Journal of Chemistry 2011 Volume 29( Issue 6) pp:1268-1272

Publication Date(Web):

DOI:10.1002/cjoc.201190235

Abstract

In the presence of cucurbit[7]uril (CB[7]), the CB[7] could react with palmatine, which served as a sensitive fluorescence probe, to form host-guest stable complexes and the fluorescence intensity of the complexes was greatly enhanced. The fluorescence intensity decreased linearly with an increasing number of L-cystine in the inclusion system. The experimental results show that there exists a competition between L-cystine and palmatine for the CB[7] hydrophobic cavity and L-cystine occupies the space of CB[7] cavity, leading palmatine molecules to be forced to reside in the aqueous environment. Based on the fluorescence quenching of the CB[7]/palmatine complexes resulting from complex formation between CB[7] and L-cystine, a spectrofluorimetric method for the determination of L-cystine in aqueous solution in the presence of CB[7] was developed. The linear relationship between the corresponding values of the fluorescence quenching ΔF and L-cystine concentration was obtained in the range of 6.0 to 1.5×10³ ng·mL⁻¹, with a correlation coefficient (r) of 0.9996. The detection limit was 2.0 ng·mL⁻¹. The application of the present method to the determination of L-cystine in tablets gave satisfactory results. This paper also discussed the mechanism of the fluorescence indicator probe.

Determination of sotalol by fluorescence quenching method

Co-reporter:Hui-Min Zhang, Ji-Yuan Yang, Li-Ming Du, Chang-Feng Li and Hao Wu

Analytical Methods 2011 vol. 3(Issue 5) pp:1156-1162

Publication Date(Web):15 Apr 2011

DOI:10.1039/C0AY00728E

Sotalol has a weak fluorescence in aqueous solutions, so using a direct fluorescent method is difficult. The competitive reaction between sotalol and palmatine for occupancy of the cucurbit[7]uril (CB[7]) cavity was studied by spectrofluorimetry. CB[7] reacts with palmatine to form complexes with strong fluorescence. However, the presence of sotalol quenches the fluorescence intensity of the complexes. We attribute this to the competition between sotalol and palmatine for occupation of the CB[7] hydrophobic cavity. Results show that sotalol occupies the space within the CB[7] cavity, forcing palmatine molecules to reside in the aqueous environment. The quenching of the CB[7]/palmatine system is fast, and the degree of quenching is proportional to the concentration of sotalol. Therefore, a new and useful spectrofluorimetric method with high sensitivity and selectivity was developed for the determination of sotalol in aqueous solutions. The proposed method is fairly accurate, simple, rapid, reproducible, and sensitive. It is also specific for the identification of sotalol. Its detection limit is 0.033 μg mL−1. This paper also discusses the competition reaction mechanism between sotalol and palmatine in the CB[7] cavity.

Determination of ethambutol by a sensitive fluorescent probe

Co-reporter:Wen-Ying Wu, Ji-Yuan Yang, Li-Ming Du, Hao Wu, Chang-Feng Li

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 2011 Volume 79(Issue 3) pp:418-422

Publication Date(Web):August 2011

DOI:10.1016/j.saa.2011.02.045

The competitive reaction between ethambutol and two fluorescent probes (i.e., berberine and palmatine) for occupancy of the cucurbit[7]uril (CB[7]) cavity was studied by spectrofluorometry. The CB[7] reacts with these probes to form stable complexes, and the fluorescence intensity of the complexes is greatly enhanced. In addition, the excitation and emission wavelengths of their complexes moved to wavelengths of 343 nm and 495 nm, respectively. However, the addition of ethambutol dramatically quenches the fluorescence intensity of the two complexes. Accordingly, a couple of new fluorescence quenching methods for the determination of ethambutol were established. The methods can be applied for quantifying ethambutol. A linear relationship between the fluorescence quenching values (ΔF) and ethambutol concentration exists in the range of 5.0–1000.0 ng mL−1, with a correlation coefficient (r) of 0.9997. The detection limit is 1.7 ng mL−1. The fluorescent probe of berberine has higher sensitivity than palmatine. This paper also discusses the mechanism of fluorescence indicator probes.Graphical abstractA sensitive method for the detection of ethambutol based on fluorescence quenching (ΔF) of cucurbit[7]uril (CB[7])/berberine (BRH) was developed. For a specific range of concentrations, the ΔF values show a good linear relationship with ethambutol. It has a detection limit of 1.7 ng mL−1. The probe can be applied to bulk and biological fluids.Highlights► We examine berberine and palmatine as fluorescent probes by spectrofluorometry. ► Establishing new fluorescence quenching methods for the determination of ethambutol. ► A linear relationship exists in the range of 5–1000 ng mL−1, the detection limit is 1.7 ng mL−1. ► Using for determination of ethambutol in bulk and biological fluids.

Determination of ofloxacin and gatifloxacin by mixed micelle-mediated cloud point extraction-fluorimetry combined methodology

Co-reporter:Hao Wu, Guo-yan Zhao, Li-ming Du

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 2010 Volume 75(Issue 5) pp:1624-1628

Publication Date(Web):May 2010

DOI:10.1016/j.saa.2010.02.031

A cloud point extraction process using mixed micelle of the anionic surfactant sodium dodecyl sulfate (SDS) and the non-ionic surfactant polyoxyethylene(7.5)nonylphenylether (PONPE 7.5) to extract two fluoroquinolone antimicrobial agents, ofloxacin and gatifloxacin, from aqueous media was investigated. The method is based on the mixed micelle-mediated extraction of fluoroquinolones in the presence of NaCl as an inducing agent in phase separation, followed by spectrofluorimetric determination. The effect of different variables such as pH, PONPE7.5 concentration, SDS concentration, NaCl concentration, cloud point temperature, and time was investigated, and optimum conditions were established. At optimum conditions, the rectilinear calibration graphs were obtained in the concentration range of 0.1–150 and 0.1–250 ng mL−1 for ofloxacin and gatifloxacin, and the limits of detection were 0.04 and 0.06 ng mL−1, respectively. The proposed procedure was applied successfully for the detection of the investigated drugs in their pharmaceutical dosage forms, in spiked plasma, spiked urine, and urine samples, with good precision and accuracy.

Supramolecular interaction of cucurbit[n]urils and coptisine by spectrofluorimetry and its analytical application

Co-reporter:Chang-Feng Li, Li-Ming Du, Wen-Ying Wu, Ai-Zhuo Sheng

Talanta 2010 Volume 80(Issue 5) pp:1939-1944

Publication Date(Web):15 March 2010

DOI:10.1016/j.talanta.2009.10.049

The supramolecular interaction of a homologous series of cucurbit[n]uril (CB[n], n = 5, 6, 7, 8) hosts and coptisine (COP) was studied by spectrofluorimetry. All of the CB[n]s were found to react with COP to form 1:1 host–guest stable complexes and the fluorescence intensity of the complexes was greatly enhanced. The apparent association constants of the complexes were 1.44 × 104, 1.28 × 104, 1.86 × 104 and 1.26 × 104 L mol−1 for CB[5], CB[6], CB[7] and CB[8], respectively. In addition, CB[5] and CB[7] exhibited a higher fluorescence signal than CB[6] and CB[8]. The fluorescence intensity of the complex with CB[7] was enhanced 70-fold compared to that of the studied drug itself. Based on the significant enhancement of fluorescence intensity of supramolecular complex, a simple, rapid, highly sensitive, and selective spectrofluorimetric method was developed for the determination of COP in aqueous solution in the presence of CB[7]. At the optimum reaction conditions, a linear relationship was obtained in the range from 0.05 to 1700 ng mL−1 with a detection limit of 0.012 ng mL−1. The proposed method was successfully applied for the determination of the drug in urine and serum samples.

Study on the inclusion interaction of cucurbit[n]urils with sanguinarine by spectrofluorimetry and its analytical application

Co-reporter:Chang-Feng Li, Li-Ming Du, Hui-Ming Zhang

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 2010 Volume 75(Issue 2) pp:912-917

Publication Date(Web):February 2010

DOI:10.1016/j.saa.2009.12.036

The characteristics of host–guest complexation between cucurbit[n]uril (CB[n], n = 5, 6, 7, 8) and sanguinarine (SA) were investigated by spectrofluorimetry. The result showed that CB[n] (n = 5, 6, 7, 8) reacted with SA to form an inclusion complex. At the optimum reaction conditions, the rectilinear calibration graphs were obtained in the range from 0.1 to 2800 ng mL−1 for the investigated drug, with correlation coefficients 0.9998, 0.9997, 0.9999 and 0.9997 and detection limits 0.052, 0.26, 0.03 and 0.058 ng mL−1 using CB[5], CB[6], CB[7], and CB[8], respectively. The apparent association constants of the complexes were 1.23 × 104, 6.73 × 103, 4.53 × 104 and 1.21 × 104 L mol−1, for the reagents in the same order. The result demonstrated that CB[7] exhibited a higher fluorescence signal than CB[5], CB[6], and CB[8]. The proposed method was successfully applied for the determination of the drug in human urine and serum samples.

Study on the inclusion interactions of berberine hydrochloride and cucurbit[7] by spectrofluorimetry

Co-reporter:Yan Ping Li, Hao Wu, Li Ming Du

Chinese Chemical Letters 2009 Volume 20(Issue 3) pp:322-325

Publication Date(Web):March 2009

DOI:10.1016/j.cclet.2008.10.045

The inclusion interaction between berberine hydrochloride (BRH) and cucurbit[7] (CB[7]) has been studied by spectrofluorimetry. The result showed that CB[7] interaction with BRH to form a stable inclusion complex with an association constant of 9.57 × 104 L/mol and the fluorescence intensity of the complex was enhanced in 17 times higher than that of the studied drug itself. Based on the significant enhancement of fluorescence intensity of BRH in inclusion complex, a spetrofluorimetric method with high sensitivity and selectivity was developed for the determination of BRH in aqueous solution. The linear range of the method was 3.2–2 × 103 ng/mL with a detection limit of 1.1 ng/mL. The proposed procedure could be applied successfully to determination of BRH remained in pharmaceutical dosage forms, spiked human plasma and urine with satisfactory results.

Determination of Pesticide Residue Cartap Using a Sensitive Fluorescent Probe

Co-reporter:Xu JING, Li-ming DU, Hao WU, Wen-ying WU, Yin-xia CHANG

Journal of Integrative Agriculture (November 2012) Volume 11(Issue 11) pp:1861-1870

Publication Date(Web):1 November 2012

DOI:10.1016/S2095-3119(12)60191-9

The insecticide cartap (CP) is non-fluorescent in aqueous solutions. This property makes its determination through direct fluorescent method difficult. In acidic medium and at room temperature, palmatine (PAL) can react with cucurbit[7]uril (CB[7]) to form stable complexes, and the fluorescence intensity of the complex is greatly enhanced. Significant quenching of the fluorescence intensity of the CB[7]-PAL complex was observed with the addition of cartap. Based on the significant quenching of the supramolecular complex fluorescence intensity, a new spectrofluorimetric method with high sensitivity and selectivity was developed to determine cartap in aqueous solution. The fluorescence quenching values (ΔF) showed good linear relationship with cartap concentrations from 0.009 to 2.4 μg mL−1 with a detection limit 0.0029 μg mL−1. The proposed method had been successfully applied to the determination of cartap residues in grain and vegetable with recoveries of 87.4-103%. In addition, the association constants of the complexes formed between the host and the guest were determined. The competing reaction and the supramolecular interaction mechanisms between the cartap and PAL as they fight for occupancy of the CB[7] cavity were studied using spectrofluorimetry, 1H NMR and molecular modeling calculations.

Spectrofluorometry determination of chelerythrine by TAIL-DLPME: ionic liquid serves as both extractant and solvent

Co-reporter:

Analytical Methods (2009-Present) 2012 - vol. 4(Issue 4) pp:

Publication Date(Web):

DOI:10.1039/C2AY00008C

In the present study, a new ionic liquid extraction method was developed for the sensitive and accurate determination of chelerythrine in an aqueous solution. The results show that chelerythrine fluorescence increases significantly in ionic liquids, with 1-hexyl-3-methy-limidazolium hexafluorophosphate ([C6MIM][PF6]) having the greatest increase. Based on the significant enhancement of extraction efficiency of chelerythrine in ionic liquids, a sensitive spectrofluorometry method for the quantitative estimation of chelerythrine was established. At optimum conditions, a linear relationship was obtained in the range of 0.2–130 ng mL−1. The detection limit was 0.059 ng mL−1. The enrichment factor was 81.7, and the extraction recovery for chelerythrine was 98.1%. The proposed method was successfully applied for the determination of the chelerythrine in urine and serum samples.

Study on the supramolecular interaction of astemizole with cucurbit[7]uril and its analytical application

Co-reporter:Guang-Quan Wang, Li-Ming Du, Yu-Hua Guo, Yan-Fang Qin, Jun-Wen Wang and Hao Wu

Analytical Methods (2009-Present) 2013 - vol. 5(Issue 1) pp:NaN179-179

Publication Date(Web):2012/11/06

DOI:10.1039/C2AY25929J

Astemizole (AST) is non-fluorescent in aqueous solution. This property makes its determination through direct fluorescence methods difficult. Reaction and supramolecular interaction mechanisms, between AST and palmatine (PAL) as they compete for occupancy of the cucurbit[7]uril (CB[7]) cavity, were studied using spectrofluorimetry, 1H NMR, and molecular modeling calculations. The association constants of the complexes formed between the host and the guest were determined. Based on the significant quenching of the supramolecular complex fluorescence intensity, a fluorescent probe method of high sensitivity and selectivity was developed to determine AST in its pharmaceutical dosage forms and in urine samples with good precision and accuracy. The linear range of the method was from 0.02 μg mL−1 to 2.2 μg mL−1. The detection limit was 0.007 μg mL−1. This shows that the proposed method has promising potential for therapeutic monitoring and pharmacokinetics and for clinical application.

Determination of Brilliant Blue FCF in food and cosmetic samples by ionic liquid independent disperse liquid–liquid micro-extraction

Co-reporter:

Analytical Methods (2009-Present) 2013 - vol. 5(Issue 16) pp:NaN4026-4026

Publication Date(Web):2013/06/05

DOI:10.1039/C3AY40362A

A novel, relatively fast and simple method of ionic liquid independent disperse liquid–liquid micro-extraction (IL-IDLLME) coupled with UV-Visible spectroscopy was developed and applied to determination of the synthetic dye Brilliant Blue FCF (E133) in six different kinds of food and cosmetic samples, namely soft drinks, candy, jelly, kiwi fruit (Actinidia chinensis) pieces, roasted pea, ice cream, eau de toilette and shampoo. The samples were dissolved in water and preconcentrated simply by using 1-decyl-3-methylimidazolium tetrafluoroborate ([C10MIM][BF4]) without a dispersive solvent, heat, ultrasonication or additional chemical reagents. The effects of different parameters such as the volume of [C10MIM][BF4], pH, KCl concentration, micro-extraction temperature, incubation time and centrifugation time on the micro-extraction of E133 (0.12 μg mL−1) were investigated and optimum conditions were established. A linear calibration curve was obtained in the range of 1.5–150 μg L−1 for E133 under optimum conditions. The limit of detection (LOD) based on 3Sb was 0.34 μg L−1 (n = 11). The relative standard deviation (R.S.D.) for 5 and 140 μg L−1 of E133 was 0.43% and 0.82% (n = 10), respectively. The method is therefore recommended for use by the quality control departments of food and cosmetic producers using E133.

Anionic surfactant coacervation extraction-magnetic solid phase microextraction for determination of malachite green

Co-reporter:

Analytical Methods (2009-Present) 2014 - vol. 6(Issue 19) pp:

Publication Date(Web):

DOI:10.1039/C4AY01144A

A novel, fast, and efficient two-step microextraction technique for preconcentration and extraction of trace amounts of malachite green in fishpond water, river water and flesh of fish was developed using spectrophotometry. MG with a pH of 6.5 was extracted and mediated by the coacervation phase of the anionic surfactant sodium dodecyl benzene sulfonate. The coacervation phase was then trapped by diatomite bonded Fe3O4 magnetic nanoparticles (DBMNPs) that can rapidly achieve two-phase separation in a magnetic field. The extracted surfactant-rich phase was diluted with ethanol and its absorbance was measured at 624 nm. A number of important parameters affecting extraction efficiency, such as the volume of extraction solvent, amount of salt, pH, amount of DBMNPs, equilibration temperature and time, were investigated. The calibration graph was linear for MG ranging from 2 ng mL−1 to 180 ng mL−1 in the initial solution, with r2 = 0.9994 (n = 10). The detection limit based on three times the standard deviation of the blank (3Sb) was 0.67 ng mL−1 and the relative standard deviation for 20 ng mL−1 of MG was 1.12% (n = 5). The method was applied to determine the trace amounts of MG from fishpond water, river water and flesh of fish.

Determination of sotalol by fluorescence quenching method

Co-reporter:Hui-Min Zhang, Ji-Yuan Yang, Li-Ming Du, Chang-Feng Li and Hao Wu

Analytical Methods (2009-Present) 2011 - vol. 3(Issue 5) pp:NaN1162-1162

Publication Date(Web):2011/04/15

DOI:10.1039/C0AY00728E

Sotalol has a weak fluorescence in aqueous solutions, so using a direct fluorescent method is difficult. The competitive reaction between sotalol and palmatine for occupancy of the cucurbit[7]uril (CB[7]) cavity was studied by spectrofluorimetry. CB[7] reacts with palmatine to form complexes with strong fluorescence. However, the presence of sotalol quenches the fluorescence intensity of the complexes. We attribute this to the competition between sotalol and palmatine for occupation of the CB[7] hydrophobic cavity. Results show that sotalol occupies the space within the CB[7] cavity, forcing palmatine molecules to reside in the aqueous environment. The quenching of the CB[7]/palmatine system is fast, and the degree of quenching is proportional to the concentration of sotalol. Therefore, a new and useful spectrofluorimetric method with high sensitivity and selectivity was developed for the determination of sotalol in aqueous solutions. The proposed method is fairly accurate, simple, rapid, reproducible, and sensitive. It is also specific for the identification of sotalol. Its detection limit is 0.033 μg mL−1. This paper also discusses the competition reaction mechanism between sotalol and palmatine in the CB[7] cavity.

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