Co-reporter:Pei Liang;Jinjin Wang;Guojiao Liu ;Jinyan Guan
Journal of Separation Science 2014 Volume 37( Issue 17) pp:2380-2387
Publication Date(Web):
DOI:10.1002/jssc.201400449
Matrix solid-phase dispersion combined with dispersive liquid–liquid microextraction has been developed as a new sample pretreatment method for the determination of four sulfonylurea herbicides (chlorsulfuron, bensulfuron-methyl, chlorimuron-ethyl, and pyrazosulfuron) in tea by high-performance liquid chromatography with diode array detection. The extraction and cleanup by matrix solid-phase dispersion was carried out by using CN-silica as dispersant and carbon nanotubes as cleanup sorbent eluted with acidified dichloromethane. The eluent of matrix solid-phase dispersion was evaporated and redissolved in 0.5 mL methanol, and used as the dispersive solvent of the following dispersive liquid–liquid microextraction procedure for further purification and enrichment of the target analytes before high-performance liquid chromatography analysis. Under the optimum conditions, the method yielded a linear calibration curve in the concentration range from 5.0 to 10 000 ng/g for target analytes with a correlation coefficients (r2) ranging from 0.9959 to 0.9998. The limits of detection for the analytes were in the range of 1.31–2.81 ng/g. Recoveries of the four sulfonylurea herbicides at two fortification levels were between 72.8 and 110.6% with relative standard deviations lower than 6.95%. The method was successfully applied to the analysis of four sulfonylurea herbicides in several tea samples.
Co-reporter:Pei Liang, Enjian Yang, Juan Yu and Lijuan Wen
Analytical Methods 2014 vol. 6(Issue 11) pp:3729-3734
Publication Date(Web):10 Mar 2014
DOI:10.1039/C4AY00019F
A novel, sensitive and environmentally friendly supramolecular solvent dispersive liquid–liquid microextraction method based on the solidification of a floating drop was developed for the preconcentration of trace lead (Pb) prior to its determination by graphite furnace atomic absorption spectrometry. In this method, a supramolecular solvent, a coacervate of reverse micelles formed by decanoic acid (DeA) dispersed in tetrahydrofuran (THF)–water mixture, was used to extract the metal chelate produced from the reaction of Pb(II) with diethyldithiocarbamate. After centrifugation, the coacervate phase floated on the surface of the solution, and was then solidified in an ice bath to favor phase separation. Several parameters that affect the extraction efficiency, such as the amount of DeA, the volume of THF, the pH of the sample solution, the concentration of the chelating agent, the extraction time and coexisting ions were systematically investigated. Under the optimized conditions, the linearity of the calibration curve was in the Pb concentration range of 0.1–30 ng mL−1 with a correlation coefficient (R2) of 0.9995. The detection limit of this method for Pb was 27 ng L−1 with an enhancement factor of 52, and the relative standard deviations for 1.0 ng mL−1 and 20 ng mL−1 of Pb were 3.2% and 2.5%, respectively. The method was successfully applied in the determination of trace amounts of Pb in food and water samples.
Co-reporter:Pei Liang;Juan Yu;Enjian Yang;Yajuan Mo
Food Analytical Methods 2014 Volume 7( Issue 7) pp:1506-1512
Publication Date(Web):2014 August
DOI:10.1007/s12161-013-9780-8
A novel method based on ultrasound-assisted surfactant-enhanced emulsification microextraction (UASEME) has been developed for the preconcentration of cobalt prior to its determination by graphite furnace atomic absorption spectrometry. In the UASEME technique, chloroform was used as the extraction solvent, sodium dodecyl sulfate was adopted as emulsifier, and ultrasound was applied to assist emulsification. There is no need of using organic dispersive solvent which is typically required in conventional dispersive liquid–liquid microextraction method. Several parameters that affect the extraction efficiency, such as the kind and volume of the extraction solvent, the type and concentration of the surfactant, pH of sample solution, concentration of the chelating agent, and extraction time and temperature were investigated and optimized. Under the optimal conditions, the linearity of calibration curve was in the range of 0.1–5 ng mL−1 with a correlation coefficient (R2) of 0.9992. An enrichment factor of 58 was achieved with a sample volume of 5.0 mL. The detection limit of this method for Co was 15.6 ng L−1, and the relative standard deviation (RSD) was 4.3 % at 1.0 ng mL−1 concentration level of Co. The accuracy of the developed method was evaluated by analysis of the certified reference materials GBW07605 tea leaf and GBW10015 spinach. The method was successfully applied to determine trace cobalt in food and water samples with satisfactory results.
Co-reporter:Pei Liang, Enjian Yang and Lijuan Wen
Analytical Methods 2013 vol. 5(Issue 17) pp:4419-4424
Publication Date(Web):02 Jul 2013
DOI:10.1039/C3AY40783G
A simple and rapid one-step displacement dispersive liquid–liquid microextraction method (D-DLLME) was developed for the selective preconcentration of silver followed by graphite furnace atomic absorption spectrometry determination. In the proposed method, Cu was reacted with diethyldithiocarbamate (DDTC) to form a Cu–DDTC complex, and it was used as a chelating agent instead of DDTC for dispersive liquid–liquid microextraction (DLLME) of silver. Because the stability of Ag–DDTC is higher than that of Cu–DDTC, Ag can displace Cu from the Cu–DDTC complex and be preconcentrated in a single DLLME procedure. Potential interference from co-existing metal ions with lower DDTC complex stability was largely eliminated as they cannot displace Cu from the Cu–DDTC complex, and the tolerance limits for these ions were improved by a long way compared with the conventional DLLME method. Under the optimal conditions, the limit of detection of this method was 16 ng L−1 (3σ) for silver, and an enhancement factor of 82 was achieved with a sample volume of 5.0 mL. The proposed method was successfully applied for the determination of trace silver in some environmental and biological samples with satisfactory results.
Co-reporter:Pei Liang, Guojiao Liu, Fang Wang, Wanting Wang
Journal of Chromatography B 2013 Volume 926() pp:62-67
Publication Date(Web):1 May 2013
DOI:10.1016/j.jchromb.2013.02.011
A novel method, ultrasound-assisted surfactant-enhanced emulsification microextraction with solidification of floating organic droplet (UASEME-SFOD), has been developed for the extraction of four strobilurin fungicides (kresoxim-methyl, picoxystrobin, pyraclostrobin and trifloxystrobin) in fruit juices. In the UASEME-SFOD technique, Tween 80 was used as emulsifier, and 1-undecanol was used as extraction solvent without using any organic dispersive solvent. Several parameters that affect the extraction efficiency, such as the kind and volume of extraction solvent, the type and concentration of the surfactant, extraction time, extraction temperature and salt addition were investigated and optimized. Under the optimum extraction condition, the method yields a linear calibration curve in the concentration range from 5 to 10,000 ng mL−1 for the targeted analytes with the correlation coefficient ranging from 0.9991 to 0.9998. The enrichment factors were in the range between 95 and 135, and the limits of detection of the method were 2–4 ng mL−1. The fruit juice samples were successfully analyzed using the proposed method, and the relative recoveries at fortified levels of 50 and 100 ng mL−1 were in the range of 82.6–97.5%.Highlights► UASEME-SFOD with HPLC was developed for the determination of strobilurin fungicides. ► The enrichment factors of this method are from 95 to 135. ► The extraction recoveries are in the range of 82.6–97.5%. ► The limits of detection are 2–4 ng mL−1.
Co-reporter:Pei Liang, Fang Wang, Qin Wan
Talanta 2013 Volume 105() pp:57-62
Publication Date(Web):15 February 2013
DOI:10.1016/j.talanta.2012.11.065
A highly efficient and environmentally friendly sample preparation method termed ionic liquid-based ultrasound-assisted emulsification microextraction (IL-USAEME) combined with high performance liquid chromatography has been developed for the determination of four fungicides (azoxystrobin, diethofencarb, pyrimethanil and kresoxim-methyl) in water samples. In this novel approach, ionic liquid (IL) was used as extraction solvent in place of the organic solvent used in conventional USAEME assay, and there is no need for using organic dispersive solvent which is typically required in the common dispersive liquid–liquid microextraction method. Various parameters that affect the extraction efficiency, such as the kind and volume of IL, ultrasound emulsification time, extraction temperature and salt addition were investigated and optimized. Under the optimum extraction condition, the linearities of calibration curves were in the range from 3 to 5000 ng mL−1 for target analytes with the correlation coefficient higher than 0.9992. The enrichment factors and the limits of detection were in the range of 88–137 and 0.73–2.2 ng mL−1, depending on the analytes. The environmental water samples were successfully analyzed using the proposed method, and the relative recoveries at fortified levels of 50 and 100 ng mL−1 were in the range of 83.9%–116.2%.Highlights► IL-USAEME combined with HPLC was developed for the determination of fungicides. ► The enrichment factors of this method are from 88 to 137. ► The extraction recoveries are in the range of 83.9–116.2%. ► The limits of detection are 0.73–2.2 ng mL−1.
Co-reporter:Pei Liang;Ehong Zhao
Microchimica Acta 2011 Volume 174( Issue 1-2) pp:153-158
Publication Date(Web):2011 July
DOI:10.1007/s00604-011-0611-6
We describe a method for displacement dispersive liquid-liquid microextraction (DLLME) along with graphite furnace atomic absorption spectrometry for the determination of Pd(II) in complex environmental samples. In this method, Cu(II) is first complexed with diethyldithiocarbamate (DDTC), and the resultant Cu-DDTC complex added to a sedimented phase and submitted to DLLME. In the second step, the sedimented phase is dispersed into the sample solution containing Pd, and another DLLME procedure is carried out. The Pd ions can displace Cu ions from the pre-extracted Cu-DDTC complex because the stability of the Pd-DDTC complex is higher than that of Cu-DDTC. As a result, Pd is preconcentrated. Potential interferences by transition metal ions of lower complex stability can be largely reduced as they cannot displace Cu from the Cu-DDTC complex. The tolerance limits for such ions are better by 2 to 4 orders of magnitude compared to conventional DLLME. The typical sample volume is 5 mL, and an enhancement factor of 96 and a detection limit (3 s) of 7.6 ng L-1 are achieved.
Co-reporter:Pei Liang, Juan Yang
Journal of Food Composition and Analysis 2010 Volume 23(Issue 1) pp:95-99
Publication Date(Web):February 2010
DOI:10.1016/j.jfca.2009.01.015
A new method for the determination of trace copper was developed by cloud point extraction preconcentration and spectrophotometry. In the proposed approach, amino acid (isoleucine) was used as the chelating agent, and Triton X-100 was selected as the surfactant. Some factors including pH of sample solution, concentration of the chelating agent and surfactant, and equilibration temperature and time, which affected the extraction efficiency of Cu and its subsequent determination, were studied and optimized. Under the optimum conditions, the calibration graph was linear in the range of 10–1000 μg L−1, preconcentration of 25 mL sample gave an enhancement factor of 22 and a detection limit of 5 μg L−1. The method was successfully applied to the determination of Cu in food and water samples.
Co-reporter:Pei Liang, Linlin Zhang, Ehong Zhao
Talanta 2010 Volume 82(Issue 3) pp:993-996
Publication Date(Web):15 August 2010
DOI:10.1016/j.talanta.2010.06.004
A novel displacement-dispersive liquid–liquid microextraction method was developed for the selective determination of trace silver in complicated samples by graphite furnace atomic absorption spectrometry. This method involves two steps of dispersive liquid–liquid microextraction (DLLME). Firstly, copper ion reacted with diethyldithiocarbamate (DDTC) to form Cu-DDTC complex and extracted with DLLME procedure using carbon tetrachloride (extraction solvent) and methanol (dispersive solvent); then, the sedimented phase was dispersed into the sample solution containing silver ion with methanol and another DLLME procedure was carried out. Because the stability of Ag-DDTC is larger than that of Cu-DDTC, Ag+ can displace Cu2+ from the pre-extracted Cu-DDTC and thus the preconcentration of Ag+ was achieved. Potential interference from co-existing transition metal ions with lower DDTC complex stability was largely eliminated as they cannot displace Cu2+ from Cu-DDTC complex. The tolerance limits for the co-existing ions were increased by a long way compared with conventional DLLME. Under the optimal conditions, the limit of detection was 20 ng L−1 (3σ) for silver with a sample volume of 5.0 mL, and an enhancement factor of 72 was achieved. The proposed method was successfully applied to determine of trace silver in some environmental and geological samples with satisfactory results.
Co-reporter:Pei Liang;Lili Peng
Microchimica Acta 2010 Volume 168( Issue 1-2) pp:45-50
Publication Date(Web):2010 February
DOI:10.1007/s00604-009-0253-0
A method was developed for the determination of silver ion (Ag) by combining dispersive liquid-liquid microextraction preconcentration with graphite furnace atomic absorption spectrometry. Diethyldithiocarbamate was used as a chelating agent, and carbon tetrachloride and methanol as extraction and dispersive solvent. Factors influencing the extraction efficiency of Ag and its subsequent determination were studied and optimized. The detection limit is 12 ng L−1 (3 s) with an enrichment factor of 132, and the relative standard deviation is 3.5% (n = 7, at 1.0 ng mL−1). The method was successfully applied to the determination of trace amounts of Ag in water samples.
Co-reporter:Pei Liang;Linlin Zhang;Lili Peng;Qian Li
Bulletin of Environmental Contamination and Toxicology 2010 Volume 85( Issue 2) pp:147-151
Publication Date(Web):2010 August
DOI:10.1007/s00128-010-0078-x
A method was developed for the determination of phthalate esters (dimethyl phthalate, diethyl phthalate, benzyl butyl phthalate, di-n-butyl phthalate, di-n-octyl phthalate and di-(2-ethylhextyl) phthalate) in soil samples. The method was based on microwave-assisted extraction of soil using acetonitrile as extractant. Phthalate esters in the extract were determined by high performance liquid chromatography with variable wavelength detector. Microwave-assisted extraction operational parameters, such as the solvent type, extraction temperature and time, were studied and optimized. Under the resultant conditions, recoveries of phthalate esters from spiked soil samples were in the range from 84 to 115% for two different spiking levels (0.1 and 0.5 μg g−1), and relative standard deviations of the recoveries were below 8%. The limits of detection ranged from 1.24 to 3.15 μg L−1. The method did not require clean-up or preconcentration steps. The obtained results showed that microwave-assisted extraction combined with high performance liquid chromatography was a fast and simple method for the determination of phthalate esters in soil samples.
Co-reporter:Pei Liang;Qian Li;Rui Liu
Microchimica Acta 2009 Volume 164( Issue 1-2) pp:119-124
Publication Date(Web):2009 January
DOI:10.1007/s00604-008-0042-1
A new method has been developed for the determination of trace molybdenum based on separation and preconcentration with TiO2 nanoparticles immobilized on silica gel (immobilized TiO2 nanoparticles) prior to its determination by graphite furnace atomic absorption spectrometry (GFAAS). The optimum experimental parameters for preconcentration of molybdenum, such as pH of the sample, sample flow rate and volume, eluent and interfering ions, have been investigated. Molybdenum can be quantitatively retained by immobilized TiO2 nanoparticles at pH 1.0 and separated from the metal cations in the solution, then eluted completely with 0.5 mol L−1 NaOH. The detection limit of this method for Mo was 0.6 ng L−1 with an enrichment factor of 100, and the relative standard deviation (RSD) was 3.4% at the 10 ng mL−1 Mo level. The method has been applied to the determination of trace amounts of Mo in biological and water samples with satisfactory results.
Co-reporter:Pei Liang, Ehong Zhao, Feng Li
Talanta 2009 Volume 77(Issue 5) pp:1854-1857
Publication Date(Web):15 March 2009
DOI:10.1016/j.talanta.2008.10.033
A new method for the determination of palladium was developed by dispersive liquid–liquid microextraction preconcentration and graphite furnace atomic absorption spectrometry detection. In the proposed approach, diethyldithiocarbamate (DDTC) was used as a chelating agent, and carbon tetrachloride and ethanol were selected as extraction and dispersive solvent. Some factors influencing the extraction efficiency of palladium and its subsequent determination, including extraction and dispersive solvent type and volume, pH of sample solution, concentration of the chelating agent and extraction time, were studied and optimized. Under the optimum conditions, the enrichment factor of this method for palladium reached at 156. The detection limit for palladium was 2.4 ng L−1 (3σ), and the relative standard deviation (R.S.D.) was 4.3% (n = 7, c = 1.0 ng mL−1). The method was successfully applied to the determination of trace amount of palladium in water samples.
Co-reporter:Pei Liang;Lili Peng;Ping Yan
Microchimica Acta 2009 Volume 166( Issue 1-2) pp:47-52
Publication Date(Web):2009 July
DOI:10.1007/s00604-009-0162-2
A new method for the determination of inorganic arsenic species (As(III) and As(V)) was developed by dispersive liquid-liquid microextraction (DLLME) separation and graphite furnace atomic absorption spectrometry (GFAAS) detection. In the pH range of 3–5, As(III) complexes with ammonium pyrrolidinedithiocarbamate (APDC) and then can be extracted into carbon tetrachloride droplets formed by injecting the binary solution of carbon tetrachloride (extraction solvent) and methanol (dispersive solvent) into the sample solution. As(V) is not extracted at the same pH conditions and remained in the aqueous phase. After extraction and phase separation by centrifugation, the enriched As(III) in the sedimented phase was determined by GFAAS. Total inorganic arsenic was determined after reduction of As(V) to As(III) with sodium thiosulfate and potassium iodide, and As(V) was calculated by difference. Under optimized conditions, the detection limits of this method for As(III) were 36 ng L−1 with an enrichment factor of 45, and the relative standard deviation (R.S.D.%) was 3.1% (n = 11, c = 1.0 ng mL−1). The method has been applied to the speciation of As(III) and As(V) in natural water samples with satisfactory results.
Co-reporter:Pei Liang, Hongbo Sang
Analytical Biochemistry 2008 Volume 380(Issue 1) pp:21-25
Publication Date(Web):1 September 2008
DOI:10.1016/j.ab.2008.05.008
A new method for the determination of trace lead was developed by dispersive liquid–liquid microextraction preconcentration and graphite furnace atomic absorption spectrometry. In the proposed approach, 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP) was used as a chelating agent, and carbon tetrachloride and ethanol were selected as extraction and dispersive solvents. Some factors influencing the extraction efficiency of lead and its subsequent determination, including extraction and dispersive solvent type and volume, pH of sample solution, concentration of the chelating agent, and extraction time, were studied and optimized. Under the optimum conditions, the enrichment factor of this method for lead was reached at 78. The detection limit for lead was 39 ng L−1 (3σ), and the relative standard deviation (RSD) was 3.2% (n = 7, c = 10 ng mL−1). The method was successfully applied to the determination of trace amounts of lead in human urine and water samples.
Co-reporter:Pei Liang, Ehong Zhao, Qiong Ding, Dan Du
Spectrochimica Acta Part B: Atomic Spectroscopy 2008 Volume 63(Issue 6) pp:714-717
Publication Date(Web):June 2008
DOI:10.1016/j.sab.2008.04.002
The potential of multiwalled carbon nanotubes (MWNTs) as solid-phase extraction adsorbent for the separation and preconcentration of gold has been investigated. Gold could be adsorbed quantitatively on MWNTs in the pH range of 1–6, and then eluted completely with 2 mL of 3% thiourea in 1 mol L− 1 HCl solution at a flow rate of 0.5 mL min− 1. A new method using a microcolumn packed with MWNTs as sorbent has been developed for the preconcentration of trace amount of Au prior to its determination by flame atomic absorption spectrometry. Parameters influencing the preconcentration of Au, such as pH of the sample, sample flow rate and volume, elution solution and interfering ions, have been examined and optimized. Under the optimum experimental conditions, the detection limit of this method for Au was 0.15 µg L− 1 with an enrichment factor of 75, and the relative standard deviation (R.S.D) was 3.1% at the 100 µg L− 1 Au level. The method has been applied for the determination of trace amount of Au in geological and water samples with satisfactory results.
Co-reporter:Pei Liang;Rui Liu;Jing Cao
Microchimica Acta 2008 Volume 160( Issue 1-2) pp:135-139
Publication Date(Web):2008 January
DOI:10.1007/s00604-007-0807-y
Single drop microextraction combined with graphite furnace atomic absorption spectrometry is introduced for the determination of trace lead in water samples. A drop of 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP) dissolved in benzene was held at the tip of a microsyringe and immerged into the sample solution which was stirred, the solvent drop interacts with the sample solution, and the analyte was extracted into the drop and concentrated. After extracting for a period of time, the drop was retracted into the microsyringe and directly injected into graphite furnace for GFAAS determination of Pb. Several factors affecting the extraction efficiency, such as pH of sample solution, drop volume, stirring rate and extraction time, were optimized. Under the optimized conditions, an enhancement factor of 16 was achieved, and the detection limits for Pb were 25 ng L−1. The relative standard deviation for seven replicate determination of 10 ng mL−1 Pb was 6.1%. The method was applied to determine trace Pb in biological samples with satisfactory results.
Co-reporter:Pei Liang;Qian Li;Jing Xu;Dan Du
Chromatographia 2008 Volume 68( Issue 5-6) pp:393-397
Publication Date(Web):2008 September
DOI:10.1365/s10337-008-0744-x
A novel method, continuous-flow microextraction (CFME) combined with liquid chromatography (LC) with variable-wavelength detector (VWD), has been developed for the determination of three phthalate esters (dimethyl phthalate (DMP), diethyl phthalate (DEP), and di-n-butyl phthalate (DnBP)) in water samples. Experimental parameters including extraction solvent, solvent drop volume, flow rate of sample solution, extraction time and ionic strength, which affected the extraction efficiency, were studied and optimized. Under the optimum extraction conditions, the method yields a linear calibration curve in the concentration range of 10–10,000 ng mL−1 for target analytes. The enrichment factors of this method for DMP, DEP and DnBP reached at 27, 44 and 20, respectively, and the detection limits were 2, 1 and 5 ng mL−1, respectively. Good repeatability of extraction was obtained with relative standard deviations below 8.6%. The results demonstrated that CFME followed by LC-VWD is a simple and reliable technique for the determination of phthalate esters in water samples.
Co-reporter:Zhimei Sun
Microchimica Acta 2008 Volume 162( Issue 1-2) pp:121-125
Publication Date(Web):2008 July
DOI:10.1007/s00604-007-0942-0
A sensitive and selective method has been developed for the speciation of chromium in water samples based on cloud point extraction (CPE) separation and preconcentration and determination by flame atomic absorption spectrometry. In the CPE method, Cr(III) reacts with acetylacetone yielding a hydrophobic complex, which is entrapped in the Triton X-100 surfactant-rich phase, whereas Cr(VI) remained in aqueous phase. Thus, separation of Cr(III) and Cr(VI) could be realized. Total chromium was determined after the reduction of Cr(VI) to Cr(III) by using ascorbic acid as reducing reagent. Under the optimal conditions, the detection limit of this method for Cr(III) was 0.32 ng mL−1 with an enrichment factor of 35, and the relative standard deviation was 3.4% (c = 100 ng mL−1, n = 7). The method has been applied to the speciation of chromium in natural water samples with satisfactory results.
Co-reporter:Rui Liu, Pei Liang
Analytica Chimica Acta 2007 Volume 604(Issue 2) pp:114-118
Publication Date(Web):5 December 2007
DOI:10.1016/j.aca.2007.10.008
A new method has been developed for the determination of gold based on separation and preconcentration with a microcolumn packed with nanometer TiO2 immobilized on silica gel (immobilized nanometer TiO2) prior to its determination by flame atomic absorption spectrometry. The optimum experimental parameters for preconcentration of gold, such as pH of the sample, sample flow rate and volume, eluent and interfering ions, have been investigated. Gold could be quantitatively retained by immobilized nanometer TiO2 in the pH range of 8–10, then eluted completely with 0.1 mol L−1 HNO3. The detection limit of this method for Au was 0.21 ng mL−1 with an enrichment factor of 50, and the relative standard deviation (R.S.D.) was 1.8% at the 100 ng mL−1 Au level. The method has been applied for the determination of trace amounts of Au in geological and water samples with satisfactory results.
Co-reporter:Pei Liang, Rui Liu
Analytica Chimica Acta 2007 Volume 602(Issue 1) pp:32-36
Publication Date(Web):17 October 2007
DOI:10.1016/j.aca.2007.09.012
A novel solid phase extraction sorbent, nanometer titanium dioxide immobilized on silica gel (immobilized nanometer TiO2), was prepared by sol–gel method, and the adsorptive potential of immobilized nanometer TiO2 for inorganic arsenic species (As(III) and As(V)) was assessed. It was found that both As (III) and As(V) could be adsorbed quantitatively on immobilized TiO2 within a pH range of 5.0–7.5, and only As(III) could be quantitatively retained on the sorbent within a pH range of 9.5–10.5 while As(V) was passed through the microcolumn without the retention. Based on this fact, a new speciation scheme for inorganic arsenic was established, which involved determining total As at pH 6.0 and As(III) at pH 10, with As(V) obtained by difference. The adsorption capacity of immobilized nanometer TiO2 for As(III) was found to be 4.22 mg g−1. Under the optimized conditions, the detection limits of this method for As(III) were 24 ng L−1 with an enrichment factor of 50, and the relative standard deviation (R.S.D.%) was 4.8% (n = 11, c = 5 ng mL−1). The proposed method has been applied to the speciation of inorganic arsenic in natural water samples with satisfactory results.
Co-reporter:Jing Xu, Pei Liang, Taozhi Zhang
Analytica Chimica Acta 2007 Volume 597(Issue 1) pp:1-5
Publication Date(Web):30 July 2007
DOI:10.1016/j.aca.2007.06.047
A fast and simple method, which involves dynamic liquid-phase microextraction followed by gas chromatography with flame ionization detection, has been developed to facilitate the identification and quantification of three phthalate esters (dimethyl phthalate (DMP), diethyl phthalate (DEP), and di-n-butyl phthalate (DnBP)) in water samples. Experimental parameters affecting the extraction efficiency, such as extraction solvent, solvent volume, dwell time and extraction frequency were investigated. Under the optimal conditions, the method yields a linear calibration curve over three orders of magnitude for the target analytes. The limits of detection of DMP, DEP and DnBP were 4.30, 0.66 and 0.43 ng mL−1, respectively, and relative standard deviations at the 100 ng mL−1 level were 6.4%, 5.4% and 5.2%, respectively (n = 6). Lake water, tap water and bottled mineral water samples were successfully analyzed using the proposed method.
Co-reporter:Pei Liang;Jing Cao;Rui Liu;Yan Liu
Microchimica Acta 2007 Volume 159( Issue 1-2) pp:35-40
Publication Date(Web):2007 June
DOI:10.1007/s00604-006-0708-5
Nanometer titanium dioxide immobilized on silica gel (immobilized nanometer TiO2) was prepared by the sol-gel method and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The adsorptive potential of immobilized nanometer TiO2 for rare earth elements (REEs) was assessed in this work. The REE ions can be quantitatively retained by immobilized nanometer TiO2 at a pH range of 6–9, and 0.5 mol L−1 HNO3 was sufficient for complete elution. A method has been developed for the determination of trace REEs based on preconcentration with a microcolumn packed with immobilized nanometer TiO2 and determination by inductively coupled plasma optical emission spectrometry (ICP-OES). The material showed relatively high chemical stability towards the action of acidic solutions. The packed microcolumn used in proposed procedure did not show any over pressure or swelling and can be used up to at least 20 adsorption-elution cycles without decrease in the performance. The optimum experimental parameters for preconcentration of REEs, such as pH of the sample, sample flow rate and volume, elution solution and interfering ions, have been investigated. The detection limits for REEs was between 3 and 57 ng L−1, and the relative standard deviations (RSDs) for the determination of REEs at 10 ng mL−1 level were found to be less than 6% when processing 100 mL sample solution. The method has been successfully applied to the determination of trace REEs in some environmental samples.
Co-reporter:Pei Liang;Qiong Ding;Yan Liu
Journal of Separation Science 2006 Volume 29(Issue 2) pp:242-247
Publication Date(Web):9 JAN 2006
DOI:10.1002/jssc.200500301
Nanometer titanium dioxide immobilized on silica gel (immobilized nanometer-scale TiO2 particles) was prepared by a sol-gel method and characterized by X-ray diffraction and scanning electron microscopy. The adsorptive behavior of Cr(III) and Cr(VI) on immobilized nanometer TiO2 was assessed. Cr(III) was selectively sorbed on immobilized nanometer TiO2 in the pH range of 7–9, while Cr(VI) was found to remain in solution. A sensitive and selective method has been developed for the speciation of chromium in water samples using an immobilized nanometer TiO2 microcolumn and inductively coupled plasma atomic emission spectrometry. Under optimized conditions (pH 7.0, flow rate 2.0 mL/min), Cr(III) was retained on the column, then eluted with 0.5 mol/L HNO3 and determined by ICP-AES. Total chromium was determined after the reduction of Cr(VI) to Cr(III) by ascorbic acid. The adsorption capacity of immobilized nanometer TiO2 for Cr(III) was found to be 7.04 mg/g. The detection limit for Cr(III) was 0.22 ng/mL and the RSD was 3.5% (n = 11, c = 100 ng/mL) with an enrichment factor of 50. The proposed method has been applied to the speciation of chromium in water samples with satisfactory results.
Co-reporter:Pei Liang;Jing Xu;Feng Song;Li Guo
Journal of Separation Science 2006 Volume 29(Issue 3) pp:366-370
Publication Date(Web):2 FEB 2006
DOI:10.1002/jssc.200500385
A new method, which involves dynamic liquid-phase microextraction followed by HPLC with variable wavelength detection, was developed to determine phoxim in water samples. Experimental parameters affecting the extraction efficiency, such as extraction solvent, solvent volume, sampling volume, dwell time, number of samplings, and salt concentration were investigated. Under the optimal extraction conditions, phoxim was found to yield a good linear calibration curve in the concentration range from 0.01 to 10 μg/mL. The LOD is 2 ng/mL, and RSD at the 100 ng/mL levels is 8.9%. Lake water and tap water samples were successfully analyzed using the proposed method.
Co-reporter:Yalan Li, Taozhi Zhang, Pei Liang
Analytica Chimica Acta 2005 Volume 536(1–2) pp:245-249
Publication Date(Web):22 April 2005
DOI:10.1016/j.aca.2004.12.033
A novel method for the determination of four volatile halohydrocarbons (CHCl3, CCl4, C2HCl3 and C2Cl4) in water is developed by combined continuous-flow liquid-phase microextraction (CFME) with gas chromatography microelectron capture detection (GC-μECD). The effects of extraction solvent type and volume, flow-rate of sample solution, sample volume and salt concentration on the extraction performance were investigated and optimized. The developed protocol was found to yield a linear calibration curve in the concentration range from 0.02 to 20 μg L−1 for the target analytes, and the detection limits were found to be in the low μg L−1 level, between 0.001 and 0.02 μg L−1. Good repeatabilities of extraction were obtained, with the R.S.D. values below 4.3%. The results demonstrated that the CFME followed with GC-μECD was a simple and reliable technique for the determination of volatile halohydrocarbons in water samples.
Co-reporter:Pei Liang;Qiong Ding;Feng Song
Journal of Separation Science 2005 Volume 28(Issue 17) pp:2339-2343
Publication Date(Web):24 OCT 2005
DOI:10.1002/jssc.200500154
The adsorption behavior of multiwalled carbon nanotubes (MWNTs) toward copper has been investigated systemically, and a new method has been developed for the determination of trace copper in water samples based on preconcentration with a microcolumn packed with MWNTs prior to its determination by flame atomic absorption spectrometry. The optimum experimental parameters for preconcentration of copper, such as pH of the sample, sample flow rate and volume, elution solution and interfering ions, have been investigated. Copper can be quantitatively retained by MWNTs in the pH range 5–8, and then eluted completely with 0.5 M HNO3. The detection limit of this method for Cu was 0.42 ng/mL, and the RSD was 3.5% at the 10 ng/mL Cu level. The method was validated using a certified reference material, and has been successfully applied for the determination of trace copper in water samples.
Co-reporter:Pei Liang, Li Guo, Yan Liu, Shi Liu, Tao-zhi Zhang
Microchemical Journal 2005 Volume 80(Issue 1) pp:19-23
Publication Date(Web):April 2005
DOI:10.1016/j.microc.2004.07.004
A new method, which involves liquid-phase microextraction (LPME) followed by high performance liquid chromatography (HPLC) with diode array detector (DAD), was developed to determine phoxim in water sample. Experimental parameters affecting the extraction efficiency, such as extraction solvent, solvent volume, agitation speed of the sample and extraction time were investigated. Under the optimal extraction conditions, phoxim was found to yield a good linear calibration curve in the concentration range from 0.01 to 5 μg mL−1. The limit of detection (LOD) is 10 ng mL−1, and relative standard deviation (RSD) at the 100 ng mL−1 levels is 8.4%. Lake water and tap water samples were successfully analyzed using the proposed method.
Co-reporter:Pei Liang, Yan Liu, Li Guo, Jing Zeng and Hanbing Lu
Journal of Analytical Atomic Spectrometry 2004 vol. 19(Issue 11) pp:1489-1492
Publication Date(Web):13 Oct 2004
DOI:10.1039/B409619C
The potential of multiwalled carbon nanotubes (MWNTs) as a solid-phase extraction adsorbent for the preconcentration of trace Cd, Mn and Ni has been investigated. The studied metal ions can be adsorbed quantitatively on MWNTs at pH 8.0, then eluted completely with 0.5 mol L−1 HNO3. The adsorption capacity of MWNTs was found to be 7.42, 4.86 and 6.89 mg g−1 for Cd, Mn and Ni, respectively. A new method using a microcolumn packed with MWNTs as sorbent has been developed for the preconcentration of trace amounts of Cd, Mn and Ni prior to their determination by inductively coupled plasma atomic emission spectrometry (ICP-AES). Parameters influencing the preconcentration of the analytes, such as pH of the sample, sample flow rate and volume, elution solution and interfering ions, have been examined. The method has been successfully applied to the determination of trace elements in some environmental samples with satisfactory results.
Co-reporter:Pei Liang, Yan Liu and Li Guo
Journal of Analytical Atomic Spectrometry 2004 vol. 19(Issue 8) pp:1006-1009
Publication Date(Web):14 Jul 2004
DOI:10.1039/B405079G
A sensitive and selective method has been developed for the determination of Mo in steel samples using a nanometre-sized titanium dioxide micro-column (20 mm × 3.0 mm id) and inductively coupled plasma atomic emission spectrometry (ICP-AES). Under the optimized conditions (pH 1.0, flow rate 1.5 mL min−1), Mo was retained on the column and separated from the iron matrix, then eluted with 0.5 mol L−1 NaOH and determined by ICP-AES. The adsorption capacity of nanometre TiO2 for Mo was found to be 2.01 mg g−1. The detection limit for Mo was 0.14 μg L−1, with an enrichment factor of 100, and the relative standard deviation (RSD) was 1.8%
(n
= 11, C = 50 μg L−1). The proposed method has been applied to the determination of Mo in certified reference steel samples with satisfactory results.
Co-reporter:
Analytical Methods (2009-Present) 2014 - vol. 6(Issue 11) pp:
Publication Date(Web):
DOI:10.1039/C4AY00019F
A novel, sensitive and environmentally friendly supramolecular solvent dispersive liquid–liquid microextraction method based on the solidification of a floating drop was developed for the preconcentration of trace lead (Pb) prior to its determination by graphite furnace atomic absorption spectrometry. In this method, a supramolecular solvent, a coacervate of reverse micelles formed by decanoic acid (DeA) dispersed in tetrahydrofuran (THF)–water mixture, was used to extract the metal chelate produced from the reaction of Pb(II) with diethyldithiocarbamate. After centrifugation, the coacervate phase floated on the surface of the solution, and was then solidified in an ice bath to favor phase separation. Several parameters that affect the extraction efficiency, such as the amount of DeA, the volume of THF, the pH of the sample solution, the concentration of the chelating agent, the extraction time and coexisting ions were systematically investigated. Under the optimized conditions, the linearity of the calibration curve was in the Pb concentration range of 0.1–30 ng mL−1 with a correlation coefficient (R2) of 0.9995. The detection limit of this method for Pb was 27 ng L−1 with an enhancement factor of 52, and the relative standard deviations for 1.0 ng mL−1 and 20 ng mL−1 of Pb were 3.2% and 2.5%, respectively. The method was successfully applied in the determination of trace amounts of Pb in food and water samples.
Co-reporter:
Analytical Methods (2009-Present) 2013 - vol. 5(Issue 17) pp:
Publication Date(Web):
DOI:10.1039/C3AY40783G
A simple and rapid one-step displacement dispersive liquid–liquid microextraction method (D-DLLME) was developed for the selective preconcentration of silver followed by graphite furnace atomic absorption spectrometry determination. In the proposed method, Cu was reacted with diethyldithiocarbamate (DDTC) to form a Cu–DDTC complex, and it was used as a chelating agent instead of DDTC for dispersive liquid–liquid microextraction (DLLME) of silver. Because the stability of Ag–DDTC is higher than that of Cu–DDTC, Ag can displace Cu from the Cu–DDTC complex and be preconcentrated in a single DLLME procedure. Potential interference from co-existing metal ions with lower DDTC complex stability was largely eliminated as they cannot displace Cu from the Cu–DDTC complex, and the tolerance limits for these ions were improved by a long way compared with the conventional DLLME method. Under the optimal conditions, the limit of detection of this method was 16 ng L−1 (3σ) for silver, and an enhancement factor of 82 was achieved with a sample volume of 5.0 mL. The proposed method was successfully applied for the determination of trace silver in some environmental and biological samples with satisfactory results.
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