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Chinese Journal of Chromatography
2018, Vol. 36, No. 9
Online: 08 September 2018

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Advances in the hyperbranched and poly amidoamine dendrimers grafting modification methods of chromatographic stationary phase GUO Dandan, ZHU Yuefeng, ZHU Yan 2018, 36 (9):  835-841.  DOI: 10.3724/SP.J.1123.2018.04010 Abstract ( 424 )   [Full Text(HTML)] () PDF (1660KB) ( 111 )   With the rapid development of chromatographic stationary-phase preparation technology, various modified methods are becoming increasingly mature, mainly including direct surface chemical reactions, agglomeration, grafting, and hyperbranched modification. Among these methods, hyperbranched modification based on polycondensation has been popular with researchers since it was proposed, and it has been applied to the preparation of various anion exchangers. Dendrimers are a class of three-dimensional, highly ordered dendritic macromolecules with perfect structure, high degree of surface functionality, and unique physicochemical properties. Recently, they have also gradually been applied in various chromatographic stationary-phase modifications and are expected to improve the structure and separation performance of the stationary phase, because its structure is similar to those of hyperbranched polymers. This article mainly summarizes the applications of hyperbranched and poly amidoamine dendrimers using grafted modification methods in the preparation of the chromatographic stationary phase. Finally, the trends and promising prospects of this field are presented.

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Tandem technologies in chromatographic analysis LIU Yujian, DU Fuyou, LIU Zhimin, SI Xiaoxi, XU Zhigang 2018, 36 (9):  842-849.  DOI: 10.3724/SP.J.1123.2018.04015 Abstract ( 521 )   [Full Text(HTML)] () PDF (1609KB) ( 118 )   The acquisition of chemical compounds information from samples depends on the separation as well as detection techniques. Usually, it is difficult to achieve the separation and identification of all components in complex samples by a simple one-dimensional chromatographic method. Thus, tandem technologies, which mainly include column tandem connection techniques, detector tandem connection techniques, and multidimensional chromatography, have aroused widespread interest. In this paper, advances in the three aforementioned tandem techniques (not including chromatography tandem mass spectrometry) since 2010 are discussed. Typical applications for obtaining more comprehensive and accurate information from samples are also reviewed. Finally, the development of chromatographic tandem technologies is summarized and future prospects are examined.

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Chromatographic behavior of basic drugs on thioether-embedded benzenesulfonate silica stationary phases WANG Xiaohuan, CHEN Lei 2018, 36 (9):  850-857.  DOI: 10.3724/SP.J.1123.2018.04005 Abstract ( 336 )   [Full Text(HTML)] () PDF (1083KB) ( 121 )   Mixed-mode chromatography (MMC) has pronounced advantages in the separation and analysis of complex samples. Compared with single-mode chromatography, the solute retention in MMC is controlled by multiple interactions, and the retention mechanism is more complicated. In this work, two thioether-embedded benzenesulfonate silica single-ligand and mixed-ligand stationary phases were prepared by thiol-ene click chemistry. The retention mechanisms of four basic drugs were investigated under various mobile phase compositions (pH, ionic and solvent strength). The results showed that both stationary phases have the mixed retention mechanism of the reverse phase and ion exchange. By changing the salt concentration of the mobile phase, the relationship between the retention factors of basic drugs and the reciprocal of ionic strength were investigated. The results indicate that a three-interaction-form model, containing reversed-phase, pure ion-exchange, and hydrophobically assisted ion-exchange interaction, is more suitable for the mechanism study of MMC. The quantitative results demonstrate that ion-exchange interaction composed of pure ion-exchange and hydrophobically assisted ion-exchange interaction is dominated on two phases. The relative contribution of each mechanism was varied with the solute, mobile phase composition, and ligand type and ratio. In addition, the hydrophobically assisted ion-exchange interaction had a significant impact on the solute retention and separation selectivity. These fundamental studies on the MMC retention mechanism are of great theoretical significance for the novel stationary phase design and the optimization of complex sample separation.

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Separation of eicosapentaenoic acid ethyl ester and docosahexaenoic acid ethyl ester by simulated moving bed chromatography DONG Qing, LI Min, YANG Yiwen, BAO Zongbi, YANG Qiwei, ZHANG Zhiguo, REN Qilong 2018, 36 (9):  858-865.  DOI: 10.3724/SP.J.1123.2018.04018 Abstract ( 484 )   [Full Text(HTML)] () PDF (3105KB) ( 164 )   Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are important ω -3 polyunsaturated fatty acids. Their physiological effects on humans are not exactly the same; therefore, the production of products with high-purity EPA or DHA monomers is significant. In this work, EPA ethyl ester (EPA-EE) and DHA ethyl ester (DHA-EE) were first separated using HPLC with poly(styrene-co-divinylbenzene) (PS/DVB) as the stationary phase. The effects of the mobile phase, PS/DVB particle diameter, and column temperature were systematically evaluated. The results showed that methanol is a suitable mobile phase, having a resolution of 2.75. By comparing resolutions, a PS/DVB particle diameter of 10 μ m was chosen; however, when the pressure drop of PS/DVB is considered, PS/DVB with a particle diameter of 20 μ m is more favorable for large-scale preparations. A column temperature of 40℃ was found to be the most feasible for maintaining efficient separation. Second, eight semi-preparative columns (150 mm×10 mm) of PS/DVB polymer were prepared for the simulated moving bed (SMB) chromatography; the homogeneity of these columns was perfect, with a relative total column porosity error of less than 1%. Finally, an EPA-EE and DHA-EE mixture was separated using the SMB chromatography, and the contents of the extract and the raffinate were determined using GC-FID. The effects of the flow rate of Zone Ⅱ and Zone Ⅲ, the flow rate of the feed, and the feed concentration were investigated. Under optimal conditions, EPA-EE and DHA-EE with favorable purities of 91.6% and 93.6%, respectively, were achievable. The recovery of the EPA-EE was 97.0% and the recovery of the DHA-EE was 91.6%. The productivity and solvent requirements were 5.97 g/(L\5h) and 1.52 L/g, respectively. Therefore, SMB chromatography is an attractive technology for the production of high-value products.

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Rapid determination of benzidine, picric acid, carbaryl, atrazine, and deltamethrin in surface water by ultra-performance liquid chromatography-tandem mass spectrometry ZHANG Ming, TANG Fangliang, XU Jianfen, ZHANG Wei, CHENG Xinliang, WANG Liqun 2018, 36 (9):  866-872.  DOI: 10.3724/SP.J.1123.2018.04025 Abstract ( 498 )   [Full Text(HTML)] () PDF (1428KB) ( 102 )   A method requiring no pre-treatment steps other than filtration, using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), has been developed and applied for the rapid determination of benzidine, picric acid, carbaryl, atrazine, and deltamethrin residues in surface water. Water samples were filtered with a 0.2-μ m syringe filter for particle removal and injected directly into the UPLC instrument. The separation was performed on a Waters Acquity UPLC HSS T3 column utilizing a gradient elution program of methanol (containing 2 mmol/L ammonium acetate) and water (containing 2 mmol/L ammonium acetate) as the mobile phases at a flow rate of 0.4 mL/min. The detection was accomplished by multiple-reaction monitoring scanning in positive/negative ion-switching electrospray ionization mode. Good linearity was observed in the range 0.10-10.0 μ g/L or 1.00-100 μ g/L for different targets with correlation coefficients of 0.996-0.999. The limits of detection (LODs) were 0.01-0.22 μ g/L. The recoveries ranged between 81.4% and 113% at three spiked levels with relative standard deviations (n=6) between 0.84% and 14.0%. The developed method was applied to the analysis of surface waters (river water and reservoir water) from Hangzhou; atrazine and deltamethrin were detected in part of the analyzed samples. This proposed method was characterized by high sensitivity and precision, extensive analytical range, and a high analytical rate, and showed suitability for the analysis of the five named pollutants in surface water.

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Determination of glyphosate, glufosinate, and main metabolite aminomethylphosphonic acid residues in dry tea using ultra-high performance liquid chromatography-tandem mass spectrometry YE Meijun, LU Xiaolei, LIU Xiangzhen, ZHANG Haihua, DU Yingying, PAN Shengdong 2018, 36 (9):  873-879.  DOI: 10.3724/SP.J.1123.2018.04026 Abstract ( 642 )   [Full Text(HTML)] () PDF (1710KB) ( 206 )   A method has been developed for the determination of glyphosate (GLY), glufosinate (GLUF), and the main metabolite aminomethylphosphonic acid (AMPA) residues in dry tea based on ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) coupled with pre-column derivatization. A systematic study of the effects of pretreatment methods including extraction and purification procedures was designed and carried out for the determination of GLY, GLUF, and AMPA. The results indicated that the optimal pretreatment method was as follows:the tea sample was first extracted by water in vortex, and then purified by a cation exchange solid-phase extraction column with the elution of 0.5% (v/v) formic acid aqueous solution. Finally, the eluant was derivatized by 9-fluorenylmethyl chloroformate, and the target compounds were separated on a C18 chromatographic column and analysed by UPLC-MS/MS (ESI+). GLY, GLUF, and AMPA showed good linearity in the range of 1-100 μ g/L, with correlation coefficients above 0.991. The limits of detection and limits of quantification were found to be 0.0160-0.0300 mg/kg and 0.0530-0.100 mg/kg, respectively. The average spiked recoveries of GLY, GLUF, and AMPA varied from 78.3% to 108% at three spiked levels (0.0500, 0.400, and 1.20 mg/kg), while the relative standard deviations ranged from 5.46% to 9.63%. The proposed method was utilized to detect 837 batches of tea samples. The detection ratios of GLY, GLUF, and AMPA were 3.46%, 0.24%, and 4.42%, respectively, while 0.24% of the investigated tea samples had values above maximum residue limits. The developed method is simple, rapid, sensitive, and accurate for the determination of GLY, GLUF, and AMPA in dry tea and may be used for routine analysis.

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Determination of 42 veterinary drug residues in common animal derived food by dispersive solid phase extraction coupled with liquid chromatography-tandem mass spectrometry QIN Ling, DONG Yalei, WANG Gangli, CAO Jin, DING Hong 2018, 36 (9):  880-888.  DOI: 10.3724/SP.J.1123.2018.04024 Abstract ( 484 )   [Full Text(HTML)] () PDF (878KB) ( 167 )   A liquid chromatography-tandem mass spectrometry method, coupled with a dispersive solid phase extraction (DSPE) procedure for sample preparation, was developed to determine 13 classes of 42 veterinary drugs in four representative animal-derived foods. The analytes were dispersed with water, extracted with acetonitrile containing 5% (v/v) formic acid, salted out by salts, and purified by DSPE. The analytes were separated on a C18 column (100 mm×2.1 mm, 2 μ m) with gradient elution using the mobile phase containing methanol and 0.1% (v/v) formic acid aqueous solution. Electrospray ionization-mass spectrometry was performed in multiple reaction monitoring mode for analysis of the 42 compounds. The correlation coefficients of the standard calibration curves for the 42 veterinary drugs were all above 0.995. Most recoveries at three spiked levels in the four representative matrixes ranged from 65.8% to 135.5%, with relative standard deviations of 0.5%-14.2% (n=6). The limits of detection (LODs, S/N=3) and the limits of quantification (LOQs, S/N=10) were 0.01-1.68 μ g/kg and 0.01-5.62 μ g/kg, respectively. The method is simple, rapid, sensitive, and suitable for the simultaneous determination of the 42 veterinary drugs in animal-derived food.

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Simultaneous rapid determination of 12 anti-allergic chemical drugs in Chinese traditional patent medicine and health food by supercritical fluid chromatography tandem mass spectrometry with solid phase extraction YANG Zhi, PENG Yan, JIN Mengna, LIN Liqin 2018, 36 (9):  889-894.  DOI: 10.3724/SP.J.1123.2018.04006 Abstract ( 515 )   [Full Text(HTML)] () PDF (837KB) ( 129 )   An analytical method was developed for simultaneous rapid determination of 12 anti-allergic chemical drugs in Chinese traditional patent medicine and health food by supercritical fluid chromatography tandem mass spectrometry with solid phase extraction (SPE-SFC-MS/MS). Samples were extracted with methanol by sonification and then purified by Oasis mixed-model cation exchange SPE. The extracts were separated on a Waters Trefoil CEL1 (150 mm×3.0 mm, 2.5 μ m) column with a mobile phase consisting of carbon dioxide-methanol containing 0.1% (v/v) ammonia water in a gradient elution mode, at a flow rate of 1.2 mL/min. The column temperature was 45℃ and the back pressure was 12.4×106 Pa. The whole analysis was completed in 10 min. The 12 anti-allergic chemical drugs were detected by an electrospray ion source in positive or negative modes with a multiple reaction monitoring (MRM) mode. The calibration curves of the 12 anti-allergic chemical drugs showed good linearities in the range of 5-250 μ g/L with the correlation coefficients (r) ≥ 0.998. The limits of detection (LODs) were 0.141-0.262 μ g/L, and the limits of quantification (LOQs) were 0.703-1.308 μ g/L. The recoveries of the 12 anti-allergic chemical drugs at spiked levels of 10, 20 and 100 μ g/L were in the range of 76.1%-112.5%, and the relative standard deviations (RSDs) were 1.1%-8.3% (n=6). The method is simple, sensitive and reliable. It has been successfully used for the detection of illegally added anti-allergic chemical drugs in Chinese traditional patent medicine and health food.

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Determination of nine phthalate ester metabolites in human urine using ultra high performance liquid chromatography-tandem triple quadrupole mass spectrometry ZHANG Xu, QIU Tian, FU Hui, YANG Yanwei, ZHAO Feng, LIN Shaobin, HU Xiaojian 2018, 36 (9):  895-903.  DOI: 10.3724/SP.J.1123.2018.04002 Abstract ( 549 )   [Full Text(HTML)] () PDF (881KB) ( 133 )   A method was developed to determine trace concentrations of phthalate ester (PAE) metabolites in human urine by using ultra high performance liquid chromatography-triple quadrupole mass spectrometry. Aliquots (2 mL) of human urine samples were purified using strong anion-exchange solid-phase extraction after enzymatic deconjugation by glucuronidase for 2 h. The separation was performed on a Waters ACQUITY UPLC BEH Phenyl column (100 mm×2.1 mm, 1.7 μ m) with gradient elution by 0.1% (v/v) acetic acid in acetonitrile and 0.1% (v/v) acetic acid aqueous solution. The concentrations of nine PAE metabolites were determined under a multiple reaction monitoring mode by negative electrospray ionization. Eight of the determined metabolites showed good linearities in the range of 0.39-200 μ g/L, and the ninth metabolite showed linearity in the range of 1.17-600 μ g/L with correlation coefficients > 0.995. The limits of detection ranged from 0.06 to 0.85 μ g/L, and the limits of quantification ranged from 0.20 to 2.80 μ g/L. The recovery rates at all three spiked levels ranged from 84.1% to 122% with relative standard deviations between 4.5% and 14.3%. The intra-and inter-day precisions were not more than 10.1% and 9.3%, respectively. The matrix effect and stability were found to be favorable for analysis. This method was utilized for the determination of 50 human urine samples. The detection rates of monocyclohexyl phthalate (MCHP) and monobenzyl phthalate (MBZP) were 0 and 44.0%, and the detection rates of the other seven PAE metabolites was 100%. This method has the advantage of convenient operation and good accuracy and stability, and is suitable for the quantitative determination of the nine PAE metabolites in human urine.

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Simultaneous determination of 12 direct dyes in cosmetics by high performance liquid chromatography PAN Cheng, WU Ling, XIE Yong, XU Wenqi, BAI Yang, HUANG Yonghui, HU Chaoyang 2018, 36 (9):  904-910.  DOI: 10.3724/SP.J.1123.2018.04014 Abstract ( 485 )   [Full Text(HTML)] () PDF (3705KB) ( 108 )   A method was developed for the simultaneous separation and determination of 12 direct dyes in cosmetics by high performance liquid chromatography (HPLC). The analytes were separated on an XB-C18 column with acetonitrile-0.02 mol/L ammonium acetate aqueous solution (pH 9.0) as the mobile phases, and were detected using a diode array detector. The results indicated that the 12 direct dyes had good linearities with correlation coefficients greater than 0.999. The limits of detection were between 0.017 μ g/g and 1.7 μ g/g. The average recoveries ranged from 85.6% to 113.4%, and the relative standard deviations (RSDs) ranged from 1.0% to 7.7%. The intra-and inter-day RSDs were 0.4%-6.5% and 0.2%-7.5%, respectively. The method is simple, rapid, accurate, and is suitable for the determination of direct dyes in cosmetics.

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High-aspect-ratio gas chromatography column based on micro-electro-mechanical system technology LUO Fan, FENG Fei, ZHAO Bin, TIAN Bowen, YANG Xuelei, ZHOU Haimei, LI Xinxin 2018, 36 (9):  911-916.  DOI: 10.3724/SP.J.1123.2018.03037 Abstract ( 387 )   [Full Text(HTML)] () PDF (2249KB) ( 111 )   Miniaturization of gas chromatography (GC) columns is one of the key problems associated with microminiaturization of a chromatograph. In this study, a GC column with high-aspect-ratio microchannel based on micro-electro-mechanical system (MEMS) technology has been designed and manufactured. Simulation and analysis by the COMSOL software revealed that the GC column has even velocity field distribution, which is crucial for improving the separation efficiency of the column. The results show that heavy hydrocarbons (C6-C10) and compounds of benzene series can be successfully separated. The number of theoretical plate is 14028 plates/m, and the resolution of C7-C8 is 10.82. Due to its advantages of smaller volume, lower energy consumption, and better separation performance, the GC column can be applied in micro gas chromatography.

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Determination of 50 pesticide residues in fruits by gas chromatography-tandem mass spectrometry MENG Zhijuan, HUANG Yunxia, ZHAO Limin, SUN Wenyi, FAN Sufang, LI Qiang, PAN Canping 2018, 36 (9):  917-924.  DOI: 10.3724/SP.J.1123.2018.04011 Abstract ( 652 )   [Full Text(HTML)] () PDF (4542KB) ( 113 )   A method for the determination of 50 pesticides in fruits by gas chromatography-tandem mass spectrometry (GC-MS/MS) was developed. The three QuEChERS methods (the original one without buffer, the one with acetate buffer and the one with citrate buffer) were compared. The purification effects of primary secondary amine (PSA) and SinChERS-Nano column were also investigated. The results showed that the acetate buffer and the citrate buffer had positive influence on the extraction compared to the original method without buffer, and there was no significant difference between the two methods using buffers. Finally, the QuEChERS method using acetate buffer was chosen as the extraction method. By comparing the purification effect images and the total ion current (TIC) chromatograms, SinChERS-Nano column was revealed to have a better cleaning effect, and was chosen for cleanup. The recoveries of methamidophos, acephate, omethoate, chlorothalonil and dicofol were in ranged of 71.2%-129.2%, the other 45 pesticides were ranged from 79.1% to 122.3%. The limits of detection (LODs) were 0.3-3.0 μ g/kg and the limits of quantification (LOQs) were 1.0-10.0 μ g/kg. The method is rapid and suitable for the screening of the 50 pesticide residues in citrus, grapes and other fruit samples.

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Analysis of fatty acid composition in cottonseed by gas chromatography with on-line pyrolytic methylation QIU Ruofeng, HUANG Zhongping, WANG Lili 2018, 36 (9):  925-930.  DOI: 10.3724/SP.J.1123.2018.04012 Abstract ( 347 )   [Full Text(HTML)] () PDF (946KB) ( 248 )   A method of on-line pyrolytic methylation-gas chromatography was developed for the analysis of fatty acid composition in cottonseed. Fatty acids in cottonseeds were converted to their corresponding fatty acid methyl esters in the presence of trimethylsulfonium hydroxide at 300℃. The major fatty acids were linoleic acid (C18:2), oleic acid (C18:1), palmitic acid (C16:0), stearic acid (C18:0), myristic acid (C14:0), palmitoleic acid (C16:1), arachidic acid (C20:0) and docosanoic acid (C22:0). The unsaturated fatty acid content varied from 66.30% to 72.54%, and linoleic acid content varied from 43.20% to 53.61%. The RSDs of the peak areas of the fatty acids were less than 10% (n=5). The fatty acid compositions in the cottonseed samples, obtained from different growing places and different edible oil samples were compared by statistical analysis. The results showed that fatty acid compositions in cottonseed samples from different regions were similar. The fatty acid composition in cottonseed samples was closest to that of corn oil, and the similarity varied from 0.960 to 0.992. The method is simple, rapid, accurate, and is suitable for the analysis of fatty acid composition in cottonseed.

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Uniform and orthogonal designs on experimental design and optimization of micellar electrokinetic capillary chromatographic method for the simultaneous analysis of three nucleoside antivirus drugs in disinfectant and anti/bacteriostatic products WANG Ping, LI Mengqi, ZHAO Liyuan, YANG Yi, DING Xiaojing 2018, 36 (9):  931-937.  DOI: 10.3724/SP.J.1123.2018.04003 Abstract ( 364 )   [Full Text(HTML)] () PDF (830KB) ( 107 )   To prevent the abuse of nucleoside-based antiviral drugs in disinfectant and anti/bacteriostatic products, a new micellar electrokinetic chromatographic (MEKC) method for the simultaneous determination of three nucleoside antiviral drugs (ganciclovir, acyclovir and penciclovir) was established. Three factors and seven levels uniform design and four factors and four levels orthogonal design were used to optimize the concentration of sodium dodecyl sulfate (SDS), sodium dihydrogen phosphate (NaH2PO4) and sodium borate (Na2B4O7) in the running buffer. The three nucleoside antiviral drugs were separated from each other in the shortest time to obtain effective separation through uniform and orthogonal designs on experimental design and optimization. The separation was performed on an uncoated fused-silica capillary with 50 μ m i. d. and a total length of 30.2 cm (effective length:20 cm). An optimized buffer solution consisting of 25 mmol/L NaH2PO4, 10 mmol/L Na2B4O7 (pH 7.41) and 140 mmol/L dodecyl sulfate sodium was used for separation. The applied voltage was 10 kV, the injected pressure and time was at 0.003 Pa for 4 s. The wavelength of the detection was 250 nm. Under the optimum conditions, the corrected area and the concentration had good linearity. The correlation coefficients (r) were not less than 0.9995. The limits of detection were all 2.0 mg/kg. The limits of quantitation were all 7.0 mg/kg. The relative recoveries ranging from 85.4% to 104.1% with RSDs all lower than 8.0%. It showed that the method was suitable for the detection of ganciclovir, acyclovir and penciclovir in disinfectant and anti/bacteriostat products with simplicity and rapidity.

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Simultaneous determination of 77 pesticide residues in eight kinds of herbal tea by liquid chromatography-tandem mass spectrometry LAN Mengzhe, LIN Xu, LIU Yaqiong, WANG Haiming, CAO Xiaoyan 2018, 36 (9):  938-945.  DOI: 10.3724/SP.J.1123.2018.04008 Abstract ( 455 )   [Full Text(HTML)] () PDF (1649KB) ( 86 )   An effective method was developed for the determination of 77 pesticide residues in eight kinds of herbal tea by modified QuEChERS and high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The target compounds were extracted with 1% (v/v) acetic acid-acetonitrile and 1 g ammonium acetate, and purified by 4 g MgSO4, 0.05 g C18, 0.50 g primary secondary amine (PSA) sorbent and 0.05 g graphitized carbon black (GCB). The 0.1% (v/v) formic acid aqueous solution and acetonitrile were used as the mobile phases. The extracts were separated on a Venusil MP C18 chromatographic column using a positive electrospray ionization (ESI) and negative ESI source under the selected ion monitoring (SIM) mode. The analytes were quantified by the matrix match standard solutions. The good linearities were obtained in the range of 0.5-100.0 μ g/L, and the correlation coefficients were all greater than 0.995. The average recoveries of the 77 pesticide residues ranged from 70.3% to 110.0%, and RSDs were in the range of 2.6%-9.8%. The limits of detection were 1.0-10.0 μ g/kg. The method is sensitive, accurate and precise, and can meet the requirements for the determination of pesticide residues.