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Chinese Journal of Chromatography
2019, Vol. 37, No. 6
Online: 08 June 2019

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Volume 37, Number 6 Content 2019, 37 (6):  0-0.  Abstract ( 84 )   PDF (4393KB) ( 32 )

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Advances in the development of detection techniques for mycotoxins in vegetable oil LI Shuangqing, LI Xiaomin, ZHANG Qinghe 2019, 37 (6):  569-580.  DOI: 10.3724/SP.J.1123.2019.01003 Abstract ( 255 )   [Full Text(HTML)] () PDF (5620KB) ( 142 )   Mycotoxins are low-molecular-weight secondary metabolites produced by different fungal species, which can cause teratogenic, hepatotoxic, nephrotoxic, carcinogenic, hemorrhagic, and immunosuppressive effects, and damage the reproductive system in humans and other mammals. Mycotoxins are often present at low concentrations in the matrices and present a branch of compounds, homologs, and isomers. Vegetable oil is one of the top mycotoxin-contaminated foods. Vegetable oil contains lipids, fatty acids, and pigments, which have the potential to increase matrix effects and damage instruments. Therefore, the establishment of high-efficient sample pretreatment methods, and highly sensitive and high-throughput detection techniques are big challenges for the accurate determination of various mycotoxins in vegetable oil. In the present study, the current status and development trends of mycotoxin detection methods in different vegetable oils have been reviewed. Different pretreatment methods such as liquid-liquid extraction, solid phase extraction, gel permeation chromatography, dynamic covalent hydrazine chemistry, and QuEChERS are also summarized. Additionally, characteristics of detection techniques such as gas chromatography, liquid chromatography, tandem mass spectrometry, and immunosensors are discussed.

Articles

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Simultaneous determination of leucovorin and 5-methyl-tetrahydrofolate diastereoisomers in human plasma by high-performance liquid chromatography-tandem mass spectrometry coupled with ultrafiltration centrifugation-based pretreatment and its application to a pharmacokinetic study XU Chenfeng, HUI Wenkai, SUN Lili, GAO Qianqian, ZOU Qiaogen 2019, 37 (6):  581-588.  DOI: 10.3724/SP.J.1123.2019.01008 Abstract ( 256 )   [Full Text(HTML)] () PDF (894KB) ( 209 )   A simple, sensitive, and stable high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was developed and validated for the simultaneous determination of leucovorin and 5-methyltetrahydrofolate diastereomers in human plasma using methotrexate as the internal standard. The analytes and the internal standard were extracted from plasma samples by simple ultrafiltration centrifugation-based extraction. The separation was achieved on a chiral HSA column (150 mm×4 mm, 5 μm) using mobile phases containing 10 mmol pH 8.0 ammonium acetate and acetonitrile in gradient mode. The method showed good linearities in the ranges of 25-5000 μg/L and 12.5-3000 μg/L for leucovorin and 5-methyltetrahydrofolate diastereoisomers, respectively. The method was fully validated with respect to sensitivity, precision, accuracy, matrix effect, extraction recovery, and stability of analytes under various conditions. The method was successfully applied to a pharmacokinetic study of 125 mg/m2 6R,S-leucovorin and 62.5 mg/m2 6S-leucovorin. The results showed that the maximum observed concentrations (Cmax) of 6S-leucovorin and L-5-methyltetrahydrofolate were (3137.917±408.837) and (1679.633±244.132) μg/L, respectively, and the areas under the curve from the time of dosing to the last measurable concentration (AUC0-t) were (7504.883±1185.101) and (14001.214±2868.949) μg/L in the 125 mg/m2 6R,S-leucovorin dose group. The Cmax values of 6S-leucovorin and L-5-methyltetrahydrofolate were (3187.917±387.298) and (1739.204±224.755) μg/L, respectively, and AUC0-t values were (7426.664±854.825) and (14884.331±1843.353) μg/L in the 62.5 mg/m2 6S-leucovorin dose group. There were no significant diffe-rences in the main pharmacokinetic parameters between the two dose groups, and the pharmacokinetic characteristics as well as the rate and extent of absorption were consistent. This method can provide technical support for future bioequivalence studies of sodium leucovorin.

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Authenticity identification of manuka honey using liquid chromatography-high resolution mass spectrometry based metabolomic technique YAN Lijuan, XU Dunming, XUE Xiaofeng, LIN Liyi, LAI Kang, WANG Jianwen, ZHANG Zhigang 2019, 37 (6):  589-596.  DOI: 10.3724/SP.J.1123.2018.12011 Abstract ( 244 )   [Full Text(HTML)] () PDF (3004KB) ( 152 )   A liquid chromatography-high resolution mass spectrometry (LC-HRMS) based metabolomic approach for the discrimination of manuka honey from the domestic honey was developed. The results of multivariate data analysis showed significant discrimination of manuka honey from domestic honey. Furthermore, a partial least squares discrimination model was established for honey discrimination, enabling the correct identification of unknown testing samples. A total of 34 highly expressed metabolic markers were obtained from the developed discrimination model, including 3-phenyllactic acid and 4-hydroxybenzoic acid which had both been previously identified as manuka honey markers. The area under the curve of the constructed marker combination reached 0.99. The developed metabolomic approach provides a new method for the quality control of manuka honey.

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Detection of free amino acids in tea using ultra-high performance liquid chromatography-tandem mass spectrometry DU Yingying, LIU Xiangzhen, YE Meijun, XU Jianfeng, GAO Haiyan, ZHENG Guojian 2019, 37 (6):  597-604.  DOI: 10.3724/SP.J.1123.2018.12041 Abstract ( 315 )   [Full Text(HTML)] () PDF (1081KB) ( 216 )   To efficiently and quickly detect free amino acid components in tea, a method using ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was developed. With the optimization of mass spectrometry, chromatographic conditions, and amino-acid extraction conditions, a total of 20 free amino acids were identified using 5 mmol/L ammonium acetate aqueous solution containing 0.2% (v/v) formic acid and methanol as mobile phases for gradient elution and detected by electrospray ionization (ESI) and positive-ion scanning. The results showed that all calibration curves expressed good linearities. Theanine (Thea), Arg, Asn, and Asp were in the range of 50-500 μg/L. The other amino acids were in the range of 10-250 μg/L with all correlation coefficients ≥ 0.99. The average recoveries were between 92.3% and 109.2%. The relative standard deviation (RSDs) were between 2.00% and 9.88%. The limits of detection (LODs) were 0.001-0.011 mg/L, and the limits of quantification (LOQs) were 0.010-0.053 mg/L. The method is sensitive, accurate, and has good repeatability and stability. The method can effectively detect 20 types of amino acids and amino components in tea leaves from the samples of green tea, white tea, and black tea.

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Determination of pyrethroid pesticides in tea by accelerated solvent extraction and ultra-performance liquid chromatography-tandem mass spectrometry JIAO Huize, LU Shiqing, HOU Di, ZHANG Qianqian 2019, 37 (6):  605-611.  DOI: 10.3724/SP.J.1123.2019.01011 Abstract ( 214 )   [Full Text(HTML)] () PDF (1303KB) ( 98 )   A method was developed for the determination of pyrethroid pesticides in tea by accelerated solvent extraction (ASE) combined with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The target compounds were extracted from tea using n-hexane and acetone (2:1, v/v) for 5 min at 10.34 MPa and 80℃ via a single cycle of accelerated solvent extraction. The extract was purified by GCB/NH2 and Florisil columns, analyzed by UPLC-MS/MS in positive electrospray ionization (ESI+) and multiple reaction monitoring (MRM) modes, and quantified by the external standard method. Regression analysis revealed that the linear relationships between mass concentration and peak area are significant for the 10 pyrethroid pesticides, and the correlation coefficients (r) are all not less than 0.9995. The limits of detection (LOD) of the 10 pyrethroid pesticides ranged from 0.5 μg/kg to 5.0 μg/kg and the limits of quantification (LOQ) ranged from 1.6 μg/kg to 16.6 μg/kg. The recoveries of all the pesticides ranged from 68.7% to 103.8% at the spiked levels of LOQ, 0.4 mg/kg and maximum residue limit (MRL) (added 1 mg/kg without MRL) with RSDs ranging from 0.8% to 13.2% (n=7). The proposed method is simple, rapid, sensitive, and accurate, and could be effective for trace analysis of pyrethroid pesticides in tea.

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Determination of 22 pesticide residues in shellfish by high performance liquid chromatography-tandem mass spectrometry FAN Guangyu, TANG Xiu, ZHANG Yunqing, MENG Xianglong, LIANG Zhengang 2019, 37 (6):  612-618.  DOI: 10.3724/SP.J.1123.2018.12026 Abstract ( 160 )   [Full Text(HTML)] () PDF (1100KB) ( 84 )   A method for the simultaneous determination of 22 pesticide residues in shellfish by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was developed. The pesticides in the samples were extracted with 0.1% (v/v) formic acid in acetonitrile, cleaned up with primary secondary amine (PSA) and graphitized carbon black (GCB), and then separated on an ACE UltraCore 2.5 Super C18 column (100 mm×2.1 mm, 2.5 μm) by elution with a methanol-0.1% (v/v) formic acid solution at a flow rate of 0.4 mL/min. The analytes were detected by electrospray ionization in the positive ion mode and the multiple reaction monitoring mode. Good linear relationships were obtained, and the correlation coefficients (r2) of the 22 pesticides were all higher than 0.997. The limits of detection and limits of quantification were 0.1-0.3 μg/kg and 0.3-1.0 μg/kg, respectively. The mean recoveries varied from 65.2% to 109.4% at three spiked levels, and the relative standard deviations ranged from 1.3% to 15.2% (n=6). The proposed method is simple, accurate, and sensitive, and is effective for the simultaneous determination of 22 pesticide residues detected in shellfish.

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Simultaneous determination of nine artificial sweeteners in food by solid-phase extraction coupled with high performance liquid chromatography-tandem mass spectrometry TANG Jiwang, YUAN Liejiang, XIAO Yong, WANG Xiu, WANG Shuxia 2019, 37 (6):  619-625.  DOI: 10.3724/SP.J.1123.2019.01012 Abstract ( 266 )   [Full Text(HTML)] () PDF (835KB) ( 233 )   A simple and rapid method based on solid-phase extraction and high performance liquid chromatography-tandem mass spectrometry for the simultaneous determination of nine artificial sweeteners (acesulfame-K, saccharin sodium, cyclamate, sucralose, aspartame, alitame, neotame, dulcin, neohesperidin dihydrochalcone) in various foods was developed. The sweeteners in food samples were extracted with triethylamine buffer solution (pH 4.5) and cleaned using an SPE column equipped with hydrophilic and lipophilic packing material. The analytes were separated on a Phenomenex Knietex® F5 column (100 mm×2.1 mm, 2.6 μm) using 0.1% (v/v) formic acid-5 mmol/L ammonium formate/methanol as a mobile phase for gradient elution, and then determined by tandem mass spectrometry in positive and negative ESI modes under multiple reaction monitoring (MRM). The internal standard method was used to further suppress the matrix effect. The method proved to be very effective in the removal of matrix interferences. Calibration curves were linear within a studied range of concentrations (r2>0.999) for the nine artificial sweeteners. The limits of detection (LODs) and limits of quantification (LOQs) were within 2-30 μg/kg and 6-100 μg/kg, respectively. The recoveries for the nine investigated sweeteners were within 86.3%-106.3% at three spiked levels, with relative standard deviations (RSDs) between 1.2% and 5.9%. The developed method is rapid, efficient, accurate, and reliable; it can also be applied for the rapid determination of other artificial sweeteners in a complex food matrix.

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Simultaneous determination of 14 sexual hormones in health care products by ultra performance liquid chromatography-atmospheric pressure chemical ionization-triple quadrupole mass spectrometry RAO Yakun, LI Zhuo, ZHANG Diyue, DONG Manman, WEI Xinghua, CHEN Dong, ZHANG Yafeng 2019, 37 (6):  626-633.  DOI: 10.3724/SP.J.1123.2018.12039 Abstract ( 150 )   [Full Text(HTML)] () PDF (931KB) ( 53 )   A comprehensive analytical method was developed for the simultaneous determination of 14 sexual hormones in health care products by ultra performance liquid chromatography-atmospheric pressure chemical ionization-triple quadrupole mass spectrometry (UPLC-APCI-MS/MS). The samples were extracted twice with acetonitrile and the extracts were purified using hydrophilic-lipophilic balance (HLB) cartridges. Chromatographic separation was achieved on a Hypersil Gold C18 column (100 mm×2.1 mm, 1.9 μm) by gradient elution with acetonitrile and 10 mmol/L ammonium acetate aqueous solution as the mobile phases. Compounds were detected by APCI-MS/MS with external standard calibration curve method. All the 14 sexual hormones showed a good linear trend in their respective concentration ranges and the correlation coefficients (r) were no less than 0.996. The limits of detection (LODs) ranged from 0.0990 μg/kg to 2.09 μg/kg. The limits of quantification (LOQs) were in the range of 0.495-5.23 μg/kg. The average recoveries of the 14 sexual hormones in the health care product samples ranged from 65.8% to 118.8% at the three spiked levels. The precisions (n=6) ranged from 0.6% to 8.7% (n=6). The method is simple, sensitive, accurate and precise, and is suitable for the determination of the illegal added sexual hormones in the health care products.

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Determination of carbonyls in ambient PM2.5 by coupling dummy template imprinting technology and high performance liquid chromatography FANG Siyang, CHEN Shili, HE Jiahua, WANG Hao, SHEN Lisi, LIU Yangyang, SUN Hui, LAI Jiaping 2019, 37 (6):  634-643.  DOI: 10.3724/SP.J.1123.2018.12012 Abstract ( 171 )   [Full Text(HTML)] () PDF (1545KB) ( 79 )   The determination of ambient carbonyls by the derivative method inevitably leads to the introduction of extra 2,4-dinitrophenylhydrazine (2,4-DNPH) into the sample solution. Traditional solid phase extraction (SPE) materials cannot remove this interference. To address this issue, a selective molecularly imprinted solid phase extraction (MISPE) column was prepared. With 2,4-dinitroaniline (2,4-DNAN) as the dummy template, MISPE could eliminate the excessive derivative agent (2,4-DNPH) in the air samples. Consequently, the sample could be concentrated effectively while the sensitivity increased greatly. By coupling MISPE and high performance liquid chromatography (HPLC), the developed method was used to study the concentration and source of 14 carbonyls of PM2.5 during spring in Guangzhou Higher Education Mega Center. Results showed that the total concentration of carbonyls increased with the level of air pollution. Particularly, the content of isovaleraldehyde increased sharply to account for 21% of the 14 total carbonyls in the haze days. Moreover, a high positive correlation between isovaleraldehyde and propionaldehyde was found either in normal days or haze days. From the correlation analysis, it was shown that anthropogenic emissions together with photochemical reaction had contributed to the abnormally high levels of carbonyls in ambient PM2.5 in the haze days. This aspect should be further investigated.

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Determination of two alkaloids in Mongolian medicine Mauleri-Dabusi-4 soup by hollow fiber liquid phase micro-extraction coupled with ultra-high performance liquid chromatography BAO Guirong, MENG He, LI Youxin, BAO James Jianmin 2019, 37 (6):  644-648.  DOI: 10.3724/SP.J.1123.2018.12029 Abstract ( 169 )   [Full Text(HTML)] () PDF (1520KB) ( 66 )   In this study, a method combining hollow fiber liquid phase micro-extraction (HF-LPME) and ultra-high performance liquid chromatography (UPLC) was developed for the determination of two alkaloids (piperine and piperlonguminine) in Mongolian medicine Mauleri-Dabusi-4 Soup. The parameters affecting the micro-extraction efficiency were evaluated and optimized. The optimum conditions were as follows:polyvinylidence fluoride HF (54% pore size); 10 g/L NaCl; 30 μ L octanol as extraction solvent; 173 r/min stirring rate of extraction; and 128 min extraction time. The extracted drug was detected by UPLC. The calibration curves obtained good linear relationship in the concentration ranges of 100-8500 and 8.3-5000 μg/L for piperine and piperlonguminine, respectively. The enrichment factors of the method for piperine and piperlonguminine were achieved to be 59 and 65. The limits of detection were 2.2 μg/L for piperine and 2.5 μg/L for piperlonguminine. The method was successfully applied for the determination of alkaloids in Mongolian medicine Mauleri-Dabusi-4.

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Determination of neohesperidin dihydrochalcone and naringin dihydrochalcone in feeds by solid phase extraction-high performance liquid chromatography PAN Cheng, HU Chaoyang, REN Xiaoying, WU Ling, HUANG Hehe, JIANG Fengling, XIE Yong, QIU Xiuyu 2019, 37 (6):  649-654.  DOI: 10.3724/SP.J.1123.2019.01006 Abstract ( 234 )   [Full Text(HTML)] () PDF (1055KB) ( 231 )   A new method was established for the determination of neohesperidin dihydrochalcone (NHDC) and naringin dihydrochalcone (Naringin DC) in feeds by solid phase extraction-high performance liquid chromatography (SPE-HPLC). The samples were extracted by methanol and were purified on an HLB solid-phase extraction column. Chromatographic separation was achieved on an XB-C18 column (150 mm×4.6 mm, 5 μm) by linear gradient elution using methanol/water as the mobile phase. The analytes were detected by the diode array detector (DAD). The results revealed a good linear correlation (r>0.999) between the peak areas and mass concentrations of dihydrochalcone sweeteners in the range of 0.2-49.0 mg/L. The limits of quantification (LOQs) of NHDC and Naringin DC were 0.02 and 0.01 mg/kg, respectively. Intra- and inter-day reproducibilities were 0.7%-4.1% and 0.9%-6.0%, respectively. The spiked recoveries for the samples and relative standard deviations (RSDs) were 86.2%-105.0% and 1.0%-6.3% (n=3), respectively. It is both sensitive and repeatable for the quantitative determination of neohesperidin dihydrochalcone and naringin dihydrochalcone in feeds, and thus, can be used to effectively reduce interference in feeds.

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Effects of microbial degradation effects based on generalized regression neural network on the detection of accelerants FANG Qiang, LIU Ling 2019, 37 (6):  655-660.  DOI: 10.3724/SP.J.1123.2018.12035 Abstract ( 139 )   [Full Text(HTML)] () PDF (902KB) ( 58 )   To explore the effects of microbial degradation at fire scenes on the identification of accelerants, samples of general and nutrient soil were injected into an accelerant, considering sealed storage time as a variable. The accelerant residues in the samples were identified through gas chromatography-mass spectrometry (GC-MS) with passive headspace pretreatment. The result indicated that the composition of the accelerants was changed due to microbial degradation, with varying degrees of degradation degree in different soil samples. Degradation in the general soil samples was superior to that in nutrient soil samples. C9 to C12 n-alkanes and monosubstituted aromatic hydrocarbons were more easily degraded, compared to other components. With the increase of substituents, the degradation of polysubstituted aromatic hydrocarbons became increasingly difficult. Principal component analysis (PCA) was used for data dimension reduction based on the type of soil samples. Generalized regression neural network (GRNN) analysis classified the soil samples with 100% accuracy.

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Simultaneous determination of vitamins B1, B2, B6, niacinamide and calcium pantothenate in compound vitamin B tablets by high performance quantitative capillary electrophoresis HU Wenwen, TAO Jianwei, WANG Qingwei, LI Jing, YAN Chao, XU Xu 2019, 37 (6):  661-665.  DOI: 10.3724/SP.J.1123.2018.12040 Abstract ( 186 )   [Full Text(HTML)] () PDF (823KB) ( 117 )   A high performance quantitative capillary electrophoresis method was developed for the simultaneous determination of vitamins B1, B2, B6, nicotinamide, and calcium pantothenate in vitamin B tablets using a quantitative capillary electrophoresis instrument. The samples were extracted ultrasonically with acetonitrile-water (20:80, v/v). The automatic high precision quantitative capillary electrophoresis instrument was used to realize quantitative injection through a 10 nL injection valve. The background electrolyte was selected as 40 mmol/L sodium borate buffer (pH 9.0), which was continuously supplied by a microfluidic injection pump. The working voltage was -10 kV. The detection wavelength of vitamins B1, B2, B6, and nicotinamide was selected as 280 nm, which was then changed to 210 nm to detect calcium pantothenate. The result showed good linearities between the peak area and the concentration of vitamins B1, B2, B6, nicotinamide, and calcium pantothenate in the correlation coefficients (r) range of 0.9968-0.9998. The limits of detection (LODs) were in the range of 2.5-36.0 mg/L. The average recoveries were 94.1%-98.9% with relative standard deviations (RSDs) as 1.3%-1.9%. The method is precise, reliable, and suitable for the simultaneous determination of vitamins B1, B2, B6, nicotinamide, and calcium pantothenate in a real compound vitamin B tablet.

Technical Notes

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Optimization of sample preparation condition for sodium dodecyl sulfate capillary electrophoresis of non-reduced monoclonal antibodies LIU Zhendong, GAO Tie, XU Lingli, YANG Yong, WANG Qingmin, CHEN Hongxu 2019, 37 (6):  666-670.  DOI: 10.3724/SP.J.1123.2018.12023 Abstract ( 519 )   [Full Text(HTML)] () PDF (802KB) ( 209 )   Sodium dodecyl sulfate capillary electrophoresis has become the mainstream method for purity analysis of monoclonal antibodies because of its advantages of fast and high resolution. Sample preparation has a significant impact on the purity detection of non-reduced monoclonal antibodies. In order to optimize sample preparation, the purity of monoclonal antibodies of different types and batches in sample buffers with iodoacetamide and N-ethyl maleimide as sulfhydryl sealants and at pH 6.0-9.0 was investigated. It was found that in the two types of sulfhydryl sealants, the high pH sample buffer could affect the sealing effect of the sulfhydryl sealant and produce more antibody fragments. Conversely, under the low pH condition, the antibody fragments were fewer and the purities of monoclonal antibodies were higher. Therefore, the sample buffer with pH 6.0 is the optimal preparation condition for the purity detection of non-reduced monoclonal antibodies.