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Chinese Journal of Chromatography
2019, Vol. 37, No. 12
Online: 08 December 2019

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Volume 37, Number 12 Content 2019, 37 (12):  0-0.  Abstract ( 20 )   PDF (5816KB) ( 30 )

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Research advances in covalent organic framework materials for sample pretreatment BAI Jing, LIN Zi'an 2019, 37 (12):  1251-1260.  DOI: 10.3724/SP.J.1123.2019.08008 Abstract ( 292 )   [Full Text(HTML)] () PDF (2618KB) ( 325 )   Covalent organic frameworks (COFs) are two-dimensional or three-dimensional crystalline porous structures formed by the covalent bonding of organic monomers. As an emerging crystalline porous material, COFs have been widely used in various fields such as gas storage, catalysis, sensing, and drug delivery. In recent years, COFs have shown immense potential in analytical chemistry because of their low density, large surface area, and controllable structure. This paper reviews the application of porous COFs and their composites in sample pretreatment, including dispersive solid-phase extraction, solid phase micro-extraction, and magnetic solid phase extraction.

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Advances in derivatization for the analysis of sialic acids by chromatography and/or mass spectrometry ZHANG Qiwei, ZHENG Qi 2019, 37 (12):  1261-1267.  DOI: 10.3724/SP.J.1123.2019.05025 Abstract ( 148 )   [Full Text(HTML)] () PDF (959KB) ( 142 )   Sialic acids are a family of 9-carbon carboxylated monosaccharides. They are widely found in vertebrates, as well as some invertebrates, fungi and bacteria. Sialic acids in the organisms exist in free form or as important components at the terminal positions of glycoconjugates. They are involved in a variety of physiological activities, and are closely related to disease, such as inflammation and cancer. Analytical methods based on chromatography and/or mass spectrometry are the most widely used for characterizing sialic acids from biological samples. In order to improve the detection sensitivity and/or efficiency of chromatographic separation, it is necessary to derivatize the sialic acids prior to analysis. A variety of derivatization methods have been developed in the past few decades. The present review focuses on the derivatization methods for the analysis of sialic acids by chromatography and/or mass spectrometry at the monosaccharide, free sialic acid, N/O-glycan and glycosphingolipid levels. The applications and development trends in this field are also prospected.

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Research progress on pretreatment and detection of bisphenols in food and environmental samples ZHANG Yujia, LING Yun, ZHANG Yuan, ZHANG Feng 2019, 37 (12):  1268-1274.  DOI: 10.3724/SP.J.1123.2019.08002 Abstract ( 259 )   [Full Text(HTML)] () PDF (908KB) ( 240 )   Bisphenols, which are environmental endocrine disruptors, are widely found in food packaging materials and the environment, polluting the ecological environment and inducing harm to human health. Bisphenol residues constitute an important food safety problem at present. Hence, detecting the bisphenol content in food and environmental samples is of great significance for protecting human health. Because of the low concentration and matrix interference, a combination of sample pretreatment and instrumental analysis is imperative for improving the detection efficiency and enhancing the analytical sensitivity and reliability. Common pretreatment and analysis methods mainly include liquid-liquid extraction, microwave-assisted extraction, solid-phase extraction, solid-phase microextraction, matrix-dispersive solid-phase extraction, and QuEChERS. Common instrumental analysis methods include liquid chromatography, gas chromatography, capillary electrophoresis, immunoassays, and biosensors. In this paper, various methods for sample pretreatment and instrumental analysis of bisphenols in food and environmental samples are reviewed, with the aim of providing a reference for the residue monitoring of bisphenols.

Articles

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Chiral stationary phases of cellulose derived using 3,5-dimethyl phenylcarbamate CHEN Xuexian, ZHANG Peng, HE Yijuan, XU Wen, YUAN Liming 2019, 37 (12):  1275-1281.  DOI: 10.3724/SP.J.1123.2019.05033 Abstract ( 114 )   [Full Text(HTML)] () PDF (6782KB) ( 107 )   Chiral columns based on cellulose tri(3,5-dimethyl phenylcarbamate) (CTDMPC) have been extensively used for enantioseparation by high-performance liquid chromatography (HPLC). The effects of cellulose derived using different amounts of 3,5-dimethyl phenylcarbamate and silica gels prepared by different methods on the chiral separation characteristics have been investigated. Thirteen chiral chromatographic columns were prepared, and their separation capability for sixteen racemate samples was evaluated. The efficiency of enantioselective resolution followed the order trisubstituted cellulose column > disubstituted cellulose column > cellulose column. Refine silica gel and macroporous silica gel showed better performance than did coarse silica gel. The use of macroporous silica gel resulted in low column pressure. Whether the silica gels were derived by aminopropyl could affect the enantioseparations. The thirteen chiral chromatographic columns were complementary for the separation of racemates, especially the cellulose column. This is a comparative study on the preparation of chiral stationary phases for HPLC, and the findings would enable us to design and fabricate chromatographic columns.

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Preparation of immobilized trypsin micro monolithic column and its application to rapid digestion of trace proteins ZHENG Mengmeng, HAN Ying, KANG Jingwu 2019, 37 (12):  1282-1290.  DOI: 10.3724/SP.J.1123.2019.08039 Abstract ( 103 )   [Full Text(HTML)] () PDF (2486KB) ( 94 )   A method for the preparation of a micro monolithic column with immobilized trypsin was developed for the rapid and efficient digestion of proteins. The micro monolithic column was prepared by photo-polymerization inside the tip of 20 μL pipette. The polymerization solution was composed of the functional monomers 4-pentenoic succinimide ester (PAS) and 2-hydroxyethyl methacrylate (HEMA), crosslinker pentaerythritol triacrylate (PETA) dissolved in a ternary porogenic system comprising dimethyl sulfoxide (DMSO), formyldimethylamine (DMF) and 1-dodecanol. Immobilization of trypsin was achieved by a chemical reaction between the amino group and succinimide. The effects of the active ester content in the polymerization mixture and the volumes of the monolithic bed on the column capacities of the immobilized trypsin were systematically investigated. The digestion efficiency as well as the stability and repeatability of the immobilized trypsin were systematically investigated by using standard proteins cytochrome C and bovine serum albumin. The experimental results indicated that high digestion efficiency with great reproducibility between batches and the digestion procedure could be obtained within 10 min. The trypsin immobilized columns were applied to the digestion of proteins extracted from 1×105 human acute promyelocytic leukemia (NB4) cells and human acute T-cell leukemia (Jurkat T) cells. A total of 2489 and 2572 proteins were readily identified by Nano-LC-MS/MS analysis. The quantity ratio of the identified proteins increased 2.2% and 6.1%, respectively, compared to the case of in-solution digestion, demonstrating the robustness of the trypsin immobilized micro column and its potential application to proteome studies.

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Determination of trihexyphenidyl in human plasma by ultra high performance liquid chromatography-tandem mass spectrometry YANG Yufei, XIA Yunyan, WU Sha, ZOU Qiaogen 2019, 37 (12):  1291-1296.  DOI: 10.3724/SP.J.1123.2019.05026 Abstract ( 138 )   [Full Text(HTML)] () PDF (909KB) ( 85 )   A sensitive and high throughput method by ultra high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was established for the determination of trihexyphenidyl in human plasma. The method was used to evaluate the bioequivalence of the test preparation and reference preparation, and to investigate the effect of food on the pharmacokinetic behavior of trihexyphenidyl. The trihexyphenidyl and internal standard trihexyphenidyl-d11 were extracted from human plasma by protein precipitation using methanol as the precipitant. Chromatographic separation was achieved on a Waters UPLC BEH C8 column (50 mm×2.1 mm, 1.7 μm) with 0.1% (v/v) formic acid aqueous solution containing 5 mmol/L ammonium acetate and acetonitrile-water (95:5, v/v) as the mobile phases. The analytes were detected by an electrospray ionization source in positive ion and multiple reaction monitoring modes. The linear range of trihexyphenidyl was 0.1-40 ng/mL. This test involved 30 healthy male and female subjects with a single oral administration of a 2-mg trihexyphenidyl hydrochloride tablet each. The 90% confidence intervals under fasting conditions of peak plasma concentration (Cmax), area under the plasma concentration-time curve (AUC0-t) and area under the plasma concentration-time curve from zero to infinity (AUC0-∞) were 82.2%-99.4%, 82.3%-97.3% and 83.4%-97.9%, and these pharmacokinetics parameters under postprandial conditions were 100.8%-122.8%, 96.8%-112.4% and 96.6%-112.1%, which were all in the range of 80.0%-125.0%, indicating that the test tablets and reference tablets were bioequivalent.

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A high-performance liquid chromatography-tandem mass spectrometry method for the quantitative determination of four genotoxic impurities in gefitinib SUN Chunyan, JI Yinghe, QIN Kunming, GAO Xun, ZHAO Longshan 2019, 37 (12):  1297-1304.  DOI: 10.3724/SP.J.1123.2019.07002 Abstract ( 136 )   [Full Text(HTML)] () PDF (2065KB) ( 107 )   In this work, a method for the determination of the amounts of the four genotoxic impurities in gefitinib has been developed. A simple and sensitive high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) approach has been developed, optimized, and validated. The genotoxic impurities were 3-chloro-4-fluoroaniline, 3,4-difluoroaniline, 3-fluoro-4-chloroaniline, and 3,4-dichloroaniline. Separation was achieved on an Inertsil ODS-3 column (100 mm×3.0 mm, 3 μm). The column temperature was 40 ℃, and the running time was 12 min. A triple quadrupole mass detector with positive electrospray ionization in the multiple reaction monitoring (MRM) mode was applied. The method was validated in terms of its specifi-city, linearity, precision, accuracy, stability, and robustness. The correlation coefficient of each impurity was higher than 0.999 in the range of 0.6-96.0 μg/L. The limits of detection (LODs) and limits of quantity (LOQs) were in the ranges of 0.2-2.0 μg/L and 0.6-6.0 μg/L, respectively. The recoveries of all impurities at 6, 30, and 60 μg/L were within 91.0%-98.5%. All impurities were stable within 2 h. After detection, only 3-chloro-4-fluoroaniline was detected in the batch number 16052301 and R16052501-1 gefitinib samples, but its concentration was below the impurity limit (6 mg/L). This method is simple, reliable, and suitable for the determination of four genotoxic impurities in gefitinib. It can be further applied as a reference for quality control.

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Differential analysis of peptides in Panax ginseng C. A. Meyer root by ultra-performance liquid chromatography-high resolution mass spectrometry ZHAO Nan, CHENG Mengchun, WU Yulin, LIU Dan, ZHANG Xiaozhe 2019, 37 (12):  1305-1313.  DOI: 10.3724/SP.J.1123.2019.09006 Abstract ( 85 )   [Full Text(HTML)] () PDF (997KB) ( 92 )   An ultra-performance liquid chromatography-high resolution mass spectrometry (UPLC-HRMS)-based peptidomics approach was developed for evaluating the similarities and differences between peptides in different morphological regions of Panax ginseng C. A. Meyer root. A total of 62 high-confidence peptides were characterized through database search, and four parts of ginseng root were all rich in peptides. The results of the differential analysis showed that the peptides were differentially expressed between the main root (MR), branch root (BR), rhizome (RH), and fibrous root (FR). Besides, a total of 25 potential peptide markers enabling the differentiation were discovered. In particular, the difference between the MR and the other parts was the most significant, and it led to a new viewpoint for the study of the difference in pharmacodynamics between the MR and the non-MR. These findings illustrate the structural diversity of ginseng peptides and reveal the similarities and differences between the peptides in ginseng root, thus providing chemical evidence for the quality control and rational application of ginseng.

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Determination of ten cephalosporins in bee products by solid phase extraction-ultra-performance liquid chromatography-tandem mass spectrometry ZHANG Hao, WU Yinliang, ZHANG Yiwen, XU Xiuqin, XU Feng 2019, 37 (12):  1314-1320.  DOI: 10.3724/SP.J.1123.2019.07028 Abstract ( 97 )   [Full Text(HTML)] () PDF (930KB) ( 81 )   An ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for the simultaneous quantitative determination of ten cephalosporins in bee products, including honey, royal jelly, and lyophilized royal jelly powder, has been established. The samples were extracted with an acetonitrile-water (80:20, v/v) solution. After purification by solid phase extraction using an Oasis PRIME HLB cartridge, the extract was blown to dryness under a stream of nitrogen gas and then re-dissolved in 1 mL 0.1% (v/v) formic acid solution and methanol (95:5, v/v). The samples were separated on an Acquity UPLC BEH C18 column, using a mixture of 0.1% (v/v) formic acid solution and methanol as the mobile phase under gradient elution. The analysis was carried out using a positive electrospray ion source in the multiple reaction monitoring mode. The matrix-matched external standard method was applied to quantitative analysis. Good linear relationships were obtained for the ten cephalosporins in certain concentration ranges, and the correlation coefficients were more than 0.999. The limits of detection and limits of quantification for the ten cephalosporins were in the ranges 0.15-1.5 μg/kg and 0.5-5 μg/kg, respectively. The recoveries for the analytes in the bee products were in the range of 75.0%to 89.8%, with relative standard deviations of 1.4% to 4.6%. This method is characterized by a short analysis time and is suitable for the determination of cephalosporins in different bee products by virtue of its simplicity and reliability.

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Determination of residual glyphosate and aminomethylphosphonic acid in wheat flour and oats samples by non-derivatization method based on ultra-performance liquid chromatography-high resolution mass spectrometry PAN Shengdong, TONG Tingde, YE Meijun, CHEN Xiaohong, JIN Micong 2019, 37 (12):  1321-1330.  DOI: 10.3724/SP.J.1123.2019.06018 Abstract ( 121 )   [Full Text(HTML)] () PDF (1421KB) ( 119 )   A rapid and accurate analysis method based on ultra-performance liquid chromatography-high resolution mass spectrometry (UPLC-HRMS) was developed for the determination of residual glyphosate (GLY) and aminomethylphosphonic acid (AMPA) in wheat flour and oats samples. The wheat flour and oats samples were firstly subjected to vortex and ultrasound extraction; then, the extract solution was purified by MCX solid-phase extraction (SPE) cartridges as well as protein precipitation using acetonitrile. The chromatographic separation was carried out on a Dikma Polyamino HILIC column (150 mm×2.0 mm, 5 μm) by linear gradient elution procedure using 5 mmol/L ammonium acetate in water (pH=10.5) and acetonitrile as the elution solvent. An electrospray ion source in negative mode and parallel reaction monitor (PRM) mode was used for quantification by the internal standard method. The instrument conditions for liquid chromatography (LC) and HRMS, and the sample pretreatment conditions for GLY and its metabolite AMPA were systematically optimized. In addition, the matrix effect and injection system residue were investigated, and a comparison of different analytical methods was carried out. The results indicated that GLY and AMPA showed good linearities in the range of 5.0-100.0 μg/L with coefficients (R2) higher than 0.999. The limits of detection (LODs) were found to be 0.005 and 0.05 mg/kg for GLY and AMPA, respectively. The recoveries of GLY and AMPA in the wheat flour and oats samples were in the range of 93.8%-115% and 89.8%-110% at the spiked levels of 0.1, 0.5, and 2.0 mg/kg, respectively, while the relative standard deviations (RSDs) were all less than 10%. The results of the matrix effect test revealed that the matrix inhibition effect could be reduced by using an isotopic internal standard with the matrix effect parameter |η|<3%. Moreover, the injection system residue was effectively controlled with a residual level of less than 1.0%. A comparison of the developed method with the reported derivatization method indicated little difference, with RSDs of 2.19% and 3.07% to the assigned value, respectively. The established analytical method was used for the Food Analysis Performance Assessment Scheme (FAPAS) proficiency test (No. 09122, GLY in oats), and the results were satisfactory with a z value of 0.2. Moreover, the result obtained using this method was very closed to the assigned value of the FAPAS QC sample, with a recovery of 102.2% (No. T09119QC, GLY in wheat flour). The proposed method is fast, simple, sensitive, and accurate, and it can be applied for the daily monitoring of GLY and its metabolite AMPA in wheat flour and oats samples.

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Determination of sodium picosulfate in enzyme products by high-performance liquid chromatography-tandem mass spectrometry HE Jiawen, WEN Jiaxin, LAI Yuhong, LIU Yaxiong, CAO Yajing, CHEN Qiao 2019, 37 (12):  1331-1336.  DOI: 10.3724/SP.J.1123.2019.05035 Abstract ( 94 )   [Full Text(HTML)] () PDF (1192KB) ( 77 )   A method based on high-performance liquid chromatography-tandem mass spectrometry was developed for the determination of sodium picosulfate in enzyme products. Sodium picosulfate is a new slimming aid that is illegally added to food products. The existing analytical methods are not suitable for application to jellies and gel candies, thus triggering the need for developing a new method. The samples were extracted with water and passed through a polyamide cartridge. The extracts were separated on a Thermo Accucore RP-MS column (100 mm×2.1 mm, 2.6 μm) using acetonitrile-10 mmol/L ammonium acetate solution (15:85, v/v) as the mobile phase. The flow rate of the mobile phase was 0.3 mL/min, and the column temperature was 35 ℃. Detection was carried out in the multiple reaction monitoring (MRM) mode. Quantification analysis was performed by the external standard method. The results showed that sodium picosulfate had a good linear relationship in the range of 5-500 μg/L, and the correlation coefficient (r) was 0.9999. The limit of detection (LOD) was 0.05 mg/kg. The average recoveries of sodium picosulfate in different matrices were in the range of 89.2%-111.8%, with the relative standard deviations (RSDs) of 2.5%-10.4%. The method was applied to the analysis of 152 samples, and 58 positive samples were detected. The positive rate was 38.2%. The developed method is accurate and sensitive, and it is suitable for detecting sodium picosulfate in enzyme products.

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Determination of indoles in plasma of polycystic ovarian syndrome patients by high performance liquid chromatography-fluorescence detection HAN Runchuan, BAN Yanna, ZHEN Qianna, ZHOU Ying, ZHANG Xiaoqing, DING Min 2019, 37 (12):  1337-1342.  DOI: 10.3724/SP.J.1123.2019.05039 Abstract ( 86 )   [Full Text(HTML)] () PDF (1015KB) ( 105 )   A new method was established for the determination of indoles (indole (IND), 3-methylindole (3-MI), indolyl-3-acetic acid (IAA) and indolyl-3-propionic acid (IPA)) in plasma by high performance liquid chromatography-fluorescence detection (HPLC-FLD). The analytes were separated simultaneously on a Shim-pack VP-ODS column (150 mm×4.6 mm, 4.6 μm) using 15 mmol/L sodium dihydrogen phosphate solution and methanol (48:52, v/v) as the mobile phases. The column temperature was 30 ℃, and the flow rate was 0.8 mL/min. The calibration curves of IND, 3-MI, IPA and IAA showed good linear relationships. The intra-day and inter-day relative standard deviations (RSDs) for the analytes were both less than 6.31%. The average recoveries of the analytes in plasma were 97.5%-107.0%. The method was successfully applied to the analysis of indoles in the plasma of healthy women of reproductive age (n=25) as controls and patients with polycystic ovarian syndrome (n=61). The results showed that the concentrations of indoles in the plasma were significantly different between the two groups, and IND was found to be a risk factor and a potential diagnostic biomarker for polycystic ovarian syndrome (PCOS). The method is simple, sensitive and suitable for use in clinical testing and laboratory research.

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Determination of three benzodiazepines in human urine by solid-phase extraction with poly [2-(acryloyloxy) ethyl] trimethyl ammonium chloride-co-ethylene glycol dimethacrylate monolithic column coupled with high performance liquid chromatography DU Li, LI Na, LIU Meikun, WANG Hanyun, ZHANG Qianying, WANG Manman, WANG Xuesheng 2019, 37 (12):  1343-1348.  DOI: 10.3724/SP.J.1123.2019.08004 Abstract ( 63 )   [Full Text(HTML)] () PDF (2036KB) ( 74 )   A polymer monolithic column was prepared in a syringe by using [2-(acryloyloxy) ethyl] trimethyl ammonium chloride (DAC) as a monomer and ethylene glycol dimethacrylate (EDMA) as a crosslinker. The obtained monolith was developed as a solid-phase extraction sorbent and used with high performance liquid chromatography (HPLC) for the analysis of three benzodiazepines (BZDs) including bromazepam (BRZ), lorazepam (LRZ) and diazepam (DZP) in urine. The effects of reaction time and the solid-phase extraction conditions (washing solution, elution solvent and volume) on the extraction efficiencies of the three BZDs were investigated. The monolithic column was successfully prepared within 4 h, and it offered 100% adsorption efficiency for the three BZDs. The urine sample (4 mL) was loaded on the monolith, washed with 4 mL of H2O, and eluted with 1 mL of ethyl acetate. Under the optimized conditions, the linear ranges were 4.0-1000 ng/mL for the three BZDs, with correlation coefficients (r) of 0.999. The limits of detection (S/N=3) and limits of quantification (S/N=10) of the three BZDs were in the range of 1.0-1.2 ng/mL and 3.3-4.0 ng/mL, respectively. The recoveries at three spiked levels (10, 25 and 50 ng/mL) of the three BZDs ranged from 81.4% to 102%, with intra-day and inter-day relative standard deviations (n=3) of 1.2%-4.5% and 2.5%-8.3%. The polymer monolithic column provided effective purification for the three BZDs in urine and the enrichment factor was 12-15. This polymer monolithic adsorbent has the advantages of easy preparation and high extraction efficiency. It is successfully applied to the determination of the three BZDs in urine samples.

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Determination of free nucleotides in infant formula by solid phase extraction-liquid chromatography YIN Lili, LI Shan, ZHOU Chuanjing, CHENG Zhi, ZHENG Hong, LIU Yanming 2019, 37 (12):  1349-1355.  DOI: 10.3724/SP.J.1123.2019.06027 Abstract ( 90 )   [Full Text(HTML)] () PDF (930KB) ( 70 )   A method for the determination of five free nucleotides in infant formula was established. The analytes were extracted by ethylene diamine tetraacetic acid and sodium chloride solution, and purified by strong anion exchange (SAX) solid-phase extraction. An Atlantis T3 reverse-phase column was applied to separate the five free nucleotides. A high performance liquid chromatography (HPLC) system equipped with a diode array detector was applied to detect the target compound, and a series of external standards were used for quantification. Good linearities (r≥0.999) were observed, with the range of 0.5-10 mg/L for the five free nucleotides. When the addition levels were 0.05-0.50 g/kg, the recoveries were between 91.1% and 112%, and the precisions were between 2.3%-4.7%. The limits of detection (LODs) and the limits of quantification (LOQs) for the five free nucleotides ranged from 0.0010 to 0.0015 g/kg and from 0.0030 to 0.0045 g/kg. In conclusion, the proposed method has several merits. First, the high accuracy and precision indicated that the quality control sample had a relative deviation of less than 10% to the median. Second, perfect anti-disturbance was observed for the complex goat milk powder. Thus, this method can provide technical support for supervision departments and guarantees healthy development of the dairy industry.

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Chiral separation of six triazole pesticide enantiomers by ultra-performance convergence chromatography and residue determination in cucumber ZHANG Wenhua, XIE Wen, HOU Jianbo, CHEN Qinke, LI Shumin, ZHU Zelong, ZOU Xuequan, XU Dunming 2019, 37 (12):  1356-1362.  DOI: 10.3724/SP.J.1123.2019.08028 Abstract ( 129 )   [Full Text(HTML)] () PDF (1242KB) ( 170 )   The separation of six triazole pesticide enantiomers (TPEs) by ultra-performance convergence chromatography (UPC2) was attempted, and residue analytical methods for these TPEs in cucumber were established. The triazole pesticides were triadimefon, triadimenol, hexaconazole, tebuconazole, bitertanol, and myclobutanil. The sample was extracted with acetonitrile and cleaned up using graphitized carbon black (GCB), a Florisil-phase extraction column, and the QuEChERS method. The treated extract was separated on an Acquity Terifoil AMY1 chromatographic column, with gradient elution using a mixture of supercritical CO2 and methanol or ethanol-isopropanol as the mobile phase. The residues of the six TPEs were quantified by the external standard method. The limits of quantitation (S/N>10) of these TPEs in cucumber were 0.1 mg/kg. The recoveries of the TPEs in cucumber at three spiked levels of 0.1, 0.2, and 0.5 mg/kg ranged from 65.1% to 116% with relative standard deviations (RSDs) of 1.0%-9.6%. The developed method facilitated the enantioseparation of the six TPEs and the accurate estimation of their residues in the cucumber matrix. This method is expected to play an important role in the production and utilization of chiral pesticides, as well as the establishment of relevant laws and regulations.

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Determination of diethyl aminoethyl hexanoate residues in apples by gas chromatography-mass spectrometry combined with improved QuEChERS KONG Xiangji, KONG Shun, ZHANG Xuemei, KONG Deyang 2019, 37 (12):  1363-1367.  DOI: 10.3724/SP.J.1123.2019.08021 Abstract ( 77 )   [Full Text(HTML)] () PDF (873KB) ( 56 )   A method was developed for the determination of diethyl aminoethyl hexanoate (DA-6) residues in apples by gas chromatography-mass spectrometry (GC-MS) combined with improved QuEChERS. The samples were first extracted with warm water, then, the extract was subjected to liquid-liquid re-extraction with dichloromethane, followed by rotary evaporation concentration. The residues were cleaned up with primary secondary amine (PSA). The analytes were separated on an HP-5 capillary column and detected using an EI source in the SIM mode. The recoveries ranged from 74.1% to 84.2% at three spiked levels, with relative standard deviations (RSDs) between 1.5% and 4.1%. The limit of detection and limit of quantification were 0.0024 mg/kg and 0.008 mg/kg, respectively. The developed method is sensitive, and practically applicable for the determination of DA-6 residues in apple samples.

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Determination of two non-phthalates plasticizers in edible oil by gas chromatography-tandem mass spectrometry HOU Jing, LIU Mengting, LI Shoudao, CHEN Dan, GUAN Zhuolong, LU Yuepeng 2019, 37 (12):  1368-1372.  DOI: 10.3724/SP.J.1123.2019.06015 Abstract ( 88 )   [Full Text(HTML)] () PDF (1274KB) ( 75 )   A gas chromatography-tandem mass spectrometry (GC-MS/MS) method was developed for the simultaneous determination of di (2-ethylhexyl) terephthalate and tris (2-ethylhexyl) trimellitate in edible oils. The plasticizers in the samples were extracted with acetonitrile. The extract was purified by freezing at -20 ℃, and determined by GC-MS/MS in selective reaction monitoring mode. For the two compounds, the limit of detection and limit of quantification were 0.03 mg/kg and 0.1 mg/kg, respectively, and the linear range was 0.1-10 mg/kg. The recoveries of the two compounds ranged from 81.04% to 108.31% at three spiked levels (0.1, 0.3, and 1.0 mg/kg), and the relative standard deviation ranged from 0.70% to 9.91%. The method is simple, accurate, and suitable for the determination of di (2-ethylhexyl) terephthalate and tris (2-ethylhexyl) trimellitate in edible oils.

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Analysis of volatile and semivolatile components of burley tobacco before and after baking by headspace solid-phase microextraction gas chromatography/mass spectrometry with chemometrics DENG Bo, WANG Weiwei, ZHANG Xiaotao, TONG Fuqiang, JI Houwei, LIU Yuming, ZHANG Li 2019, 37 (12):  1373-1382.  DOI: 10.3724/SP.J.1123.2019.05044 Abstract ( 90 )   [Full Text(HTML)] () PDF (2790KB) ( 112 )   The volatile and semivolatile components in burley tobacco leaves were analyzed by headspace solid-phase microextraction gas chromatography/mass spectrometry (HS-SPME-GC/MS). Twenty milligrams of tobacco powder was incubated at 60 ℃ for 8 min and then extracted using 65 μm polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber for 40 min. Finally, the fiber was desorbed at 250 ℃ for 3 min. One hundred twenty two kinds of volatile and semivolatile components in the burley tobacco leaves were tentatively identified by comparing with standard products and mass spectrometry databases, and these compounds were semi-quantitatively analyzed by the internal standard method. The differences between the volatile and semivolatile components for the burley tobacco leaves before and after baking were discriminated and visualized by principal component analysis (PCA) and partial least-squares discriminant analysis (PLS-DA). This method has the advantages of small sample size, simple pretreatment, and high sensitivity. In combination with chemometrics, the HS-SPME-GC/MS method is suitable for discriminating changes in the chemical composition of burley tobacco before and after baking, and hence has broad prospective application in the optimization of the baking conditions used for burley tobacco.

Technical Notes

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Rapid analysis of the specific migration of seven terephthalates and benzoates from plastic food contact material and products by high performance liquid chromatography-ultraviolet detection XIAO Xiaofeng, WANG Jianling, LIU Tingfei, HE Jun, CHEN Tong, WANG Ji 2019, 37 (12):  1383-1391.  DOI: 10.3724/SP.J.1123.2019.06021 Abstract ( 87 )   [Full Text(HTML)] () PDF (953KB) ( 100 )   A method based on high-performance liquid chromatography-ultraviolet (HPLC-UV) detection was developed for the rapid analysis of the specific migration of seven terephthalates and benzoates (TPBAs) in seven food simulants (10% (v/v) ethanol, 3% (m/v, i. e. 3 g/100 mL) acetic acid, 4% (v/v) acetic acid, 20% (v/v) ethanol, 50% (v/v) ethanol, 95% (v/v) ethanol, or olive oil)). Detailed comparisons were made on the extraction or purification of the seven TPBAs in olive oil food simulants by solvents, QuEChERS dSPE EMR-Lipid technology, and Captiva EMR-Lipid technology. The seven TPBAs were separated completely within 17 min by gradient elution on a phenyl column using water and methanol as the mobile phase. The detection wavelength was set at 237 nm. The injection volume was 10 μL. The linearities of the seven TPBAs were good, with r≥0.9998 at 1-80 mg/L or 8-160 mg/kg in the seven food simulants. The average recoveries of the seven TPBAs were between 91.7% and 106%, with relative standard deviations (RSDs) between 0.1% and 3.1% (n=6). The limits of quantification were 0.2-8.1 mg/kg. This method is simple, with convenient pretreatments, good chromatographic separation and linear relationships, as well as satisfactory recoveries and RSDs. The method has been applied to detect the specific migration of the seven TPBAs in real samples.