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Chinese Journal of Chromatography
2011, Vol. 29, No. 10
Online: 28 October 2011

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Highlights of research on graphene in sample preparation FENG Yuqi; LUO Yanbo 2011, 29 (10):  947-948.  DOI: 10.3724/SP.J.1123.2011.00957 Abstract ( 1453 )   [Full Text(HTML)] () PDF (125KB) ( 953 )

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Droplet microfluidics: technologies and applications XIAO Zhiliang, ZHANG Bo* 2011, 29 (10):  949-956.  DOI: 10.3724/SP.J.1123.2011.00949 Abstract ( 2319 )   [Full Text(HTML)] () PDF (663KB) ( 1043 )   Droplet microfluidics is a new area in microfluidics research and has been extensively studied and reported due to its various unique advantages. In this paper, we review the preparation and wide range of manipulation technologies of microdroplets including splitting, coalescence, mixing, sorting, storage, coding, etc., as well as their applications in chemical and biochemical analyses; we also envision the future developments of droplet microfluidic technologies.

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Preparation and application of perfluorodecyl modified silica monolithic capillary column in extraction and enrichment of perfluorooctane sulfonates HUANG Ke1, ZHOU Naiyuan2, CHEN Bo1* 2011, 29 (10):  957-961.  DOI: 10.3724/SP.J.1123.2011.00957 Abstract ( 1662 )   [Full Text(HTML)] () PDF (221KB) ( 455 )   A perfluorodecyl modified silica monolithic capillary column has been prepared by using sol-gel method. The preparation steps included hydrolysis of alkoxy silane, fasculation of silanol, gelation, aging, meso-pore preparation, drying and surface modification. It could be used as a solid phase extraction (SPE) microcolumn for extraction and enrichment of perfluorooctane sulfonate (PFOS). The enrichment characteristics and efficiency of the perfluorodecyl modified monolithic silica capillary column has been investigated and compared with C18 silica monolithic capillary column. The results indicated that the perfluorodecyl modified silica monolithic capillary column (15 cm×75 μm) had a higher adsorption capacity and a better enrichment selectivity for PFOS. The average adsorption capacity of the perfluorodecyl modified silica monolithic capillary column was 75 ng. And when the PFOS mass concentration in sample was 0.25 mg/L, the enrichment factor was 29-fold in average. Owing to the good performance of the perfluorodecyl modified silica monolithic capillary column, it can be used for the extraction and enrichment of trace PFOS in water to meet the requirements of water quality monitoring and analysis.

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Determination of virginiamycin M1 in feeds by ultra high performance liquid chromatography-tandem mass spectrometry HUANG Yonghui* 2011, 29 (10):  962-966.  DOI: 10.3724/SP.J.1123.2011.00962 Abstract ( 1834 )   [Full Text(HTML)] () PDF (176KB) ( 556 )   A comprehensive analytical method based on ultra high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) has been developed for the determination of virginiamycin M1 in feeds. The sample was extracted twice by ultrasonic extraction with acetonitrile-0.2% (v/v) formic acid (8:2, v/v). The chromatographic separation was achieved with a BEH C18 column and acetonitrile-0.3%(v/v) formic acid （35:65, v/v） as the mobile phase. The identification and quantification of the analyte were carried out on electrospray ionization MS/MS in a multiple reaction monitoring (MRM) mode. The correlation coefficient (r) of virginiamycin M1 was 0.9995 in the linear range of 0.3~226.6 μg/L. The detection limit (S/N=3) and quantification limit (S/N=10) of virginiamycin M1 were 2 μg/kg and 7 μg/kg, respectively. The average spiked recoveries were in the range of 82.6% to 102.7% with the relative standard deviations (RSDs) of 0.9%~10.5%. The results demonstrate that the proposed method is simple, sensitive, repeatable and suitable for the testing of virginiamycin M1 in feeds.

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Determination of linuron and its metabolite 3,4-dichloroaniline residues in meat and meat products using liquid chromatography-tandem mass spectrometry GUO Dehua, YI Xionghai*, QU Li 2011, 29 (10):  967-973.  DOI: 10.3724/SP.J.1123.2011.00967 Abstract ( 1936 )   [Full Text(HTML)] () PDF (298KB) ( 498 )   A method of liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed for the determination of linuron and its metabolite 3,4-dichloroaniline residues in pork, liver, kidney, casings, canned steam pork and sausage. The sample was extracted with a mixture of acetone-acetonitrile (5:95, v/v). Most of the lipids in the extract were eliminated by freezing-lipid filtration. After Florisil solid phase extraction cleanup, the linuron and its metabolite residues were determined by LC-MS/MS, and quantified by internal standard method. In the range of 1~500 μg/L, both linuron and 3,4-dichloroaniline showed good linearity with the correlation coefficients (r) more than 0.998. The limit of quantification (S/N＞10) was 10 μg/kg, and the limit of detection (S/N＞3) was 5 μg/kg for each analyte. The recoveries of linuron and 3,4-dichloroaniline in meat and meat products at three spiked levels were in the ranges of 88.3%~101.2% and 91.6%~101.6%, and the relative standard deviations were in the ranges of 4.8%~13.7% and 4.7%~11.8%, respectively. The results demonstrated that the proposed method can meet the requirements for the determination of linuron and 3,4-dichloroaniline in meat and meat products.

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Determination of 88 pesticide residues in cranberry plant extract by gas chromatography-triple quadrupole tandem mass spectrometry HUANG Jiangrui1,2, KONG Xianghong1*, YAO Binghua2, HE Qiang1, HAO Kaituo1,2 2011, 29 (10):  974-982.  DOI: 10.3724/SP.J.1123.2011.00974 Abstract ( 1858 )   [Full Text(HTML)] () PDF (312KB) ( 639 )   A method by using a modified QuEChERS (quick, easy, cheap, effective, rugged and safe) and gas chromatography-triple quadrupole tandem mass spectrometry (GC-MS/MS) was established to analyze 88 pesticide residues in cranberry plant extract. The sample was extracted with acetone-hexane (1:1, v/v) containing 1% acetic acid, then cleaned-up by ethylenediamine-N-propyl silyl (PSA) and graphite carbon (GCB). The extract was determined by GC-MS/MS in multi-reaction monitoring (MRM) mode, and external standard method was applied to quantified the pesticides. All the 88 pesticides showed good linearity in the range of 0.001~0.2 mg/L, and the limits of quantification (LOQs, S/N≥10) were all less than 31.5 μg/kg. The average recoveries of all the pesticides were in the range of 71.4% to 116.6% at three spiked levels of 5, 25 and 50 μg/kg in cranberry plant extract, with the relative standard deviations (RSDs) of 2.4%~16.9%. The results demonstrated that this method is simple, rapid and suitable for the determination of 88 pesticide residues in cranberry plant extract. The analytical sensitivity and accuracy can meet the requirements of multiple pesticide residue analysis.

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Analysis of six acidic components in hops extracts by high performance liquid chromatography CAI Xiaoming1, XIA Lu2, SUN Yuanshe2,3, LI Tong2,3, XIA Mingzhu1* 2011, 29 (10):  983-987.  DOI: 10.3724/SP.J.1123.2011.00983 Abstract ( 1523 )   [Full Text(HTML)] () PDF (210KB) ( 448 )   A method of high performance liquid chromatography (HPLC) was developed for the separation and determination of six acidic components (cohumulone, humulone, adhumulone, colupulone, lupulone and adlupulone) in hops extracts. The effects of several important factors, such as the addition of acid, the organic solvent of elution solution and the column temperature, were investigated to acquire the optimum conditions. The separation was carried out on a Hypersil ODS2 column (250 mm×4.6 mm, 5 μm). A mixture of acetonitrile-0.1%(v/v) phosphoric acid solution (pH 2.2) (65:35, v/v) was used as the mobile phase at a flow rate of 1.0 mL/min in isocratic elution mode. The column temperature was kept at room temperature, and the detection wavelength was set at 315 nm. The six acidic components reached baseline separation, and were identified by ultraviolet spectroscopy, infrared spectroscopy and mass spectrometry. The results show that this method is suitable for the analysis of acidic components in hops extracts owing to the stable and simple performance.

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Influences of ion-suppressors on retention behaviors of nine food additives in reversed-phase high performance liquid chromatographic separation ZHAO Yonggang, CHEN Xiaohong, LI Xiaoping, YAO Shanshan, JIN Micong* 2011, 29 (10):  988-994.  DOI: 10.3724/SP.J.1123.2011.00988 Abstract ( 2108 )   [Full Text(HTML)] () PDF (297KB) ( 475 )   The influences of ion-suppressors on retention behaviors of nine food additives, i.e., acesulfame, saccharin, caffeine, aspartame, benzoic acid, sorbic acid, stevioside, dehydroacetic acid and neotame in reversed-phase high performance liquid chromatographic (RP-HPLC) separation were investigated. The organic modification effects of acids, i.e., trifluoroacetic acid (TFA) and buffer salts, i.e., TFA-ammonium acetate (AmAc) were studied emphatically. The relationships between retention factors of solutes and volume percentages of ion-suppressors in the mobile phase systems of acetonitrile-TFA aqueous solution and acetonitrile-TFA-AmAc aqueous solution were quantitatively established, separately. The separation of nine food additives was completed by a gradient elution with acetonitrile-TFA (0.01%, v/v)-AmAc (2.5 mmol/L) aqueous solution as the mobile phases. An RP-HPLC method was established for the simultaneous determination of nine food additives in red wine. In the range of 10.0~100.0 mg/L, nine food additives showed good linearity with the correlation coefficients (r2) larger than 0.9991. The limits of detection (LODs) were in the range of 0.33~2.36 mg/L and the limits of quantification (LOQs) were in the range of 1.11~7.80 mg/L. The spiked recoveries were between 87.61% and 108.4% with the relative standard deviations (RSDs) of 2.2%~9.4%. These results are of referential significance for the rapid establishment and accurate optimization of RP-HPLC separation for the simultaneous determination of food additives in other foods.

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Simultaneous determination of four fat-soluble vitamins by microemulsion liquid chromatography YANG Jianrui, HUANG Lina, HUANG Guangliang, LI Ning* 2011, 29 (10):  995-999.  DOI: 10.3724/SP.J.1123.2011.00995 Abstract ( 1773 )   [Full Text(HTML)] () PDF (182KB) ( 498 )   A novel system was developed for the rapid determination of fat-soluble vitamins A, D2, D3 and E with microemulsion liquid chromatography (MELC). The effects of operating parameters on the separation selectivity were investigated. The optimized microemulsion system consisted of 98%(v/v) of 50 g/L sodium dodecyl sulfate (SDS)-10%(w/w) n-butanol-1.0% (w/w) n-octane-84% water (w/w) and 2%(v/v) acetonitrile. The type and content of surfactant, the content of oil phase and the organic additive (acetonitrile) were found to play important roles in the separation of four fat-soluble vitamins. The four analytes were baseline separated within 20 min on a Venusil ASB C18 column (150 mm×4.6 mm, 5 μm) with a flow rate of 0.7 mL/min and the detection wavelength of 265 nm at 40 ℃. The relative standard derivations (RSDs, n=5) of retention times and peak areas of the analytes were less than 2.3% and 3.0%, respectively. The linear ranges of vitamins A, D2, D3 and E were 22.0~88.0 mg/L, 20.2~81.0 mg/L, 24.3~97.2 mg/L and 125.0~500.0 mg/L, with their correlation coefficients (r2) of 0.9996, 0.9994, 0.9998 and 0.9998, respectively. The detection limits (S/N=3) were 0.37, 0.34, 0.41 and 2.12 mg/L, respectively. This method was successfully applied to the determination of commercial Vitamins with Minerals Tablets (21), and the results were satisfactory.

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Simultaneous determination of exogenous phosphocreatine and its metabolite creatine in rabbit plasma using ion-pair reversed-phase high performance liquid chromatography XI Heng1, HAN Guozhu1, L Li1*, ZHANG Di2 2011, 29 (10):  1000-1004.  DOI: 10.3724/SP.J.1123.2011.01000 Abstract ( 1936 )   [Full Text(HTML)] () PDF (179KB) ( 574 )   A method for simultaneous determination of exogenous phosphocreatine (PCr) and its metabolite creatine (Cr) in rabbit plasma was developed by using an ion-pair reversed-phase high performance liquid chromatography (IP-RP-HPLC). The pharmacokinetics (PK) of PCr was also investigated. In the IP-RP-HPLC method, a Kromasil C18 column was used with methanol and phosphate buffer containing tetrabutylammonium hydrogen sulfate (TBA, ion-pair reagent) as the mobile phases in a gradient elution mode, while changing detection wavelength and flow rate. The internal standard method was used to quantify PCr and Cr, and the baseline subtraction method was applied. The calibration curves showed good linearity ranged from 10 to 7500 mg/L for PCr and from 10 to 1500 mg/L for Cr, and the correlation coefficients (r) were greater than 0.999. The methodology validation showed high specificity, precision and recovery with the intra-day and inter-day relative standard deviations (RSDs) of not more than 6.2%, accuracies of 96.5%~102.4%, and extraction recoveries of more than 92%. After intravenous injection of PCr, the concentration-time profile can be best described by two-compartment model with elimination half time of (20.4±2.7) min, apparent volume of distribution of (0.179±0.037) L/kg and clearance rate of (0.019±0.002) L/(kg\5min). The Cr appeared rapidly with time to maximal concentration of 30 min, elimination half time of (43.7±4.5) min. The results of practical application showed that this bio-analytical method can completely meet the requirements for PK study of PCr in rabbit plasma.

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Simultaneous determination of ibuprofen and arginine in ibuprofen injection using ultra performance liquid chromatography LIU Jing, MA Hequn, ZHU Meng, WANG Huan, ZHANG Tianhong* 2011, 29 (10):  1005-1009.  DOI: 10.3724/SP.J.1123.2011.01005 Abstract ( 1922 )   [Full Text(HTML)] () PDF (183KB) ( 576 )   An ultra performance liquid chromatography-photodiode array detector (UPLC-PDA) method was developed for the determination of ibuprofen and the solubilizer arginine in ibuprofen injection. 2,4-Dinitroflurobenzene (DNFB) was used as the precolumn derivatization reagent. The separation of ibuprofen and arginine derivative was performed on a BEH C18 column (50 mm×2.1 mm, 1.7 μm) with the mobile phase consisting of acetonitrile-0.05 mol/L potassium dihydrogen phosphate (pH 2.5) in a gradient elution mode at a flow rate of 0.4 mL/min. Ultraviolet absorption detection wavelengths were set at 357 nm for arginine derivative and 220 nm for ibuprofen. The column temperature was set at 30 ℃. Good linearities were obtained in the ranges of 2.0~100.5 mg/L for ibuprofen and 1.7~84.5 mg/L for arginine, both with the correlation coefficients (r) of 0.9997. The spiked recoveries were 99.8% and 99.6% with the relative standard deviations (RSDs) of 0.37% and 0.25% for ibuprofen and arginine, respectively. Their respective limits of quantification (LOQs) (S/N=10) were 0.1 ng and 0.2 ng, and the limits of detection (LODs) (S/N=3) were 0.03 ng and 0.05 ng. The results demonstrated that the proposed method is simple, accurate, reproducible and suitable for the quality control of ibuprofen injection.

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High throuput analysis of organophosphorus pesticide residues and their metabolites in animal original foods by dual gas chromatography-dual pulse flame photometric detection YANG Lixin1,2,3, LI Heli1, MIAO Hong1*, ZENG Fangang2, LI Ruifeng1, CHEN Huijing1, ZHAO Yunfeng1, WU Yongning1 2011, 29 (10):  1010-1019.  DOI: 10.3724/SP.J.1123.2011.01010 Abstract ( 2058 )   [Full Text(HTML)] () PDF (413KB) ( 465 )   A method was established for quantitative determination of 45 organophosphorus pesticide residues and their metablites in animal original foods by dual gas spectrometry – dual pulse flame photometric detection. Homogenized samples were extracted with acetone and methylene chloride, and cleaned up by GPC. The response of each analyte showed a good linearity with its concentration with the linearity correlation not less than 0.99. The recovery experiments were performed by blank sample spiked at the low, medium and high fortification levels. The recoveries for beef, mutton, pork, chicken were in the range of 50.5 % ~ 128.1 % with the relative standard deviations (RSD, n=6) of 1.1 % ~ 24.4 %. The limits of detection for the analytes were in the range of 0.001 ~ 0.170 mg/kg, and the limits of quantification were in the range of 0.002 ~ 0.455 mg/kg. Animal original food samples collected from market such as meat, liver and kidney were analyzed, and residues of dichlorovis and disulfoton-sulfoxide were detected in some of those samples.

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Establishment of capillary electrophoresis fingerprints of Xiaoyao Pills SUN Guoxiang*, DING Guoyu 2011, 29 (10):  1020-1026.  DOI: 10.3724/SP.J.1123.2011.01020 Abstract ( 1852 )   [Full Text(HTML)] () PDF (261KB) ( 417 )   The capillary electrophoresis fingerprint (CEFP) of Xiaoyao Pills (XYP) was established by capillary zone electrophoresis (CZE). The quadrilateral method was developed for the optimization of the background electrolyte (BGE), and the running voltage, the compositions and pH of BGE, and so on, were evaluated by the chromatographic fingerprint resolution index (RF). An uncoated fused silica capillary column (70 cm×75 μm, the effective length of 57 cm) was employed; 50 mmol/L sodium borate-50 mmol/L Na2HPO4-150 mmol/L NaH2PO4-50 mmol/L NaHCO3 (1:1:1:5, v/v/v/v, adjusted to pH 7.40) was used as the ideal BGE. The detection wavelength was set at 228 nm, and a voltage of 12 kV and hydrodynamic pressure injection in 25 s at the height of 14 cm were applied. The CEFPs from 13 batches of XYPs containing 21 common peaks were obtained with good precision and reproducibility, in which caffeic acid was selected as the reference peak. Cluster analysis indicated that 10 out of 13 batches of XYP samples can be deemed as the reference CEFP (RCEFP). The whole 13 batches of XYP were evaluated by the systematic quantified fingerprint method (SQFM) with the RCEEP as the qualified model. The results indicated that the contents of S10 and S12 were obviously higher, the chemical constituents quantity and distributed proportion of S3 were not qualified, while the others were completely qualified. It is concluded that the method can be applied to the optimization of BGE in CZE in traditional Chinese medicine separation; and the established CEFPs of XYP can be served as a novel reference to identify and control the quality of XYP.

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Simultaneous determination of chromium speciation in cosmetics using reversed-phase ion-pair chromatography-inductively coupled plasma mass spectrometry PANG Yanhua*, LIU Mingyang, LIU Shuyan, DONG Zhenlin 2011, 29 (10):  1027-1030.  DOI: 10.3724/SP.J.1123.2011.01027 Abstract ( 1589 )   [Full Text(HTML)] () PDF (167KB) ( 419 )   A method was developed to determine chromium speciation simultaneously in cosmetics using reversed-phase ion-pair chromatography (RP-IPC) with inductively coupled plasma mass spectrometry (ICP-MS). After the extraction with disodium ethylenediaminetetraacetate(EDTA) in a water bath, the sample was separated on an XDB C18 column with the mobile phase of 5% (v/v) methanol-2.0 mmol/L tetrabutylammonium (TBA) (pH 6.0), the flow rate of 1.0 mL/min and the injection volume of 100 μL. The collision cell technology was applied to eliminate the mass interferences of 40Ar12C+and 35Cl16O1H+in the analysis of 52Cr+. The separation was achieved within 5 min. The recoveries of Cr(III) and Cr(VI) ranged from 82.7% to 107.2% with the relative standard deviations (RSDs) less than 5.62%(n=6) with the spiked amounts of 0.01~0.50 μg in different kinds of cosmetic samples. The developed method has the advantages of simplicity, sensitivity and good reproducibility, and can be used for the simultaneous determination of Cr(III) and Cr(VI) in cosmetics.

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Simultaneous determination of chromium speciation in cosmetics using reversed-phase ion-pair chromatography-inductively coupled plasma mass spectrometry BIAN Zhaoyang, TANG Gangling*, CHEN Zaigen, PANG Yongqiang, JIANG Xingyi, HU Qingyuan 2011, 29 (10):  1031-1035.  DOI: 10.3724/SP.J.1123.2011.01031 Abstract ( 1735 )   [Full Text(HTML)] () PDF (165KB) ( 478 )   A method was developed to determine chromium speciation simultaneously in cosmetics using reversed-phase ion-pair chromatography (RP-IPC) with inductively coupled plasma mass spectrometry (ICP-MS). After the extraction with disodium ethylenediaminetetraacetate(EDTA) in a water bath, the sample was separated on an XDB C18 column with the mobile phase of 5% (v/v) methanol-2.0 mmol/L tetrabutylammonium (TBA) (pH 6.0), the flow rate of 1.0 mL/min and the injection volume of 100 μL. The collision cell technology was applied to eliminate the mass interferences of 40Ar12C+and 35Cl16O1H+in the analysis of 52Cr+. The separation was achieved within 5 min. The recoveries of Cr(III) and Cr(VI) ranged from 82.7% to 107.2% with the relative standard deviations (RSDs) less than 5.62%(n=6) with the spiked amounts of 0.01~0.50 μg in different kinds of cosmetic samples. The developed method has the advantages of simplicity, sensitivity and good reproducibility, and can be used for the simultaneous determination of Cr(III) and Cr(VI) in cosmetics.

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Rapid determination of trace iodate using monolithic column ion-pair chromatography coupled with direct conductivity detection LIU Yuzhen, YU Hong*, LI Siwen 2011, 29 (10):  1036-1040.  DOI: 10.3724/SP.J.1123.2011.01036 Abstract ( 1529 )   [Full Text(HTML)] () PDF (166KB) ( 395 )   A method was developed on a monolithic column for the fast determination of trace iodate (IO~3) by ion-pair chromatography with direct conductivity detection. The analytes were separated using a mobile phase of tetrabutylammonium hydroxide (TBA)-phthalic acid-acetonitrile on a reversed-phase silica-based monolithic column. The effects of eluent, flow rate and column temperature on the retention of iodate were investigated. The optimized chromatographic conditions for the determination of the anion were as follows: 0.25 mmol/L TBA-0.18 mmol/L phthalic acid-3% acetonitrile (pH 5.5) as mobile phase, a flow rate of 4.0 mL/min and a column temperature of 30 ℃. Under the optimal conditions, retention time of iodate was less than 0.5 min and the baseline separation of iodate was achieved without any interference by other anions (Cl~, NO~3, SO2~4, I~). The detection limit (S/N=3) was 0.36 mg/L for IO~3. Relative standard deviation (RSD, n=5) of chromatographic peak area and retention time were 0.35% and 0.28%, respectively. The proposed method was applied to the determination of trace iodate in iodized medicine. The spiked recovery of iodate was 96.4%. The method is rapid, simple, accurate, reliable, and practical.

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Rapid determination of trace iodate using monolithic column ion-pair chromatography coupled with direct conductivity detection GU Weigang1, ZHANG Jinjie1, XIN Mei2, YAO Yanjia1, JI Rong1, L Bingbing1, CHEN Jianchu1* 2011, 29 (10):  1041-1045.  DOI: 10.3724/SP.J.1123.2011.01041 Abstract ( 2085 )   [Full Text(HTML)] () PDF (190KB) ( 494 )   A method was developed on a monolithic column for the fast determination of trace iodate (IO~3) by ion-pair chromatography with direct conductivity detection. The analytes were separated using a mobile phase of tetrabutylammonium hydroxide (TBA)-phthalic acid-acetonitrile on a reversed-phase silica-based monolithic column. The effects of eluent, flow rate and column temperature on the retention of iodate were investigated. The optimized chromatographic conditions for the determination of the anion were as follows: 0.25 mmol/L TBA-0.18 mmol/L phthalic acid-3% acetonitrile (pH 5.5) as mobile phase, a flow rate of 4.0 mL/min and a column temperature of 30 ℃. Under the optimal conditions, retention time of iodate was less than 0.5 min and the baseline separation of iodate was achieved without any interference by other anions (Cl~, NO~3, SO2~4, I~). The detection limit (S/N=3) was 0.36 mg/L for IO~3. Relative standard deviation (RSD, n=5) of chromatographic peak area and retention time were 0.35% and 0.28%, respectively. The proposed method was applied to the determination of trace iodate in iodized medicine. The spiked recovery of iodate was 96.4%. The method is rapid, simple, accurate, reliable, and practical.