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Chinese Journal of Chromatography
2016, Vol. 34, No. 2
Online: 08 February 2016

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Annual Reviews

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Annual review of capillary electrophoresis technology in 2015 WANG Xiaoqian, ZHAO Xinying, LIU Pinduo, WEI Qiang, QU Feng 2016, 34 (2):  121-129.  DOI: 10.3724/SP.J.1123.2016.01007 Abstract ( 725 )   [Full Text(HTML)] () PDF (878KB) ( 180 )   This paper reviews the capillary electrophoresis (CE) in 2015. The literatures searched from ISI Web of Science ranged in 2015.1.1-2015.12.31 are classified and introduced based on CE-MS method, methodology research, detection and enrichment, chiral separation and basic applications of CE. Six international and two national conferences are included and the important reports are introduced briefly. In the end, the standards of CE method for the analyses of monoclonal antibodies, water, wines and food approved in China and some other countries are listed.

Reviews

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Research development of designing flow cells for optical absorption detectors YANG Sandong, TANG Tao, LI Tong, WANG Fengyun, HAO Qingli 2016, 34 (2):  130-139.  DOI: 10.3724/SP.J.1123.2015.11005 Abstract ( 559 )   [Full Text(HTML)] () PDF (2089KB) ( 123 )   The optical absorption detector is one of the most commonly used detectors for high performance liquid chromatography (HPLC). As a core part of this kind of detector, the designs of flow cells, where light passes through samples for acquiring samples information, will affect the performance of a detector. In order to enhance the signal to noise ratio of detectors and reduce the bands broadening that come from flow cells, it is necessary to design a flow cell with a longer optical path length and a less cell volume while maintaining the luminous flux. However the limitations of the machining capacity make it difficult to increase the optical path length, reduce the cell volume and keep or increase the luminous flux simultaneously. It is a challenge to optimize the designing and machining of flow cells so as to improve the performance of detectors. This review discusses the development of designing flow cells based on the detection principle in some aspects of increasing the optical path length, reducing the cell volume, taking the advantages of total reflection and so on. At the same time, some of the designs are illustrated in detail. These various ideas and structures are significant references for designing flow cells and developing optical absorption detectors.

Articles

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Microdevice for the investigation of high-glucose induced lifespan and the protective effect of polydatin in C. elegans ZHU Guoli, YIN Fangchao, WANG Li, ZHANG Min, JIANG Lei, QIN Jianhua 2016, 34 (2):  140-145.  DOI: 10.3724/SP.J.1123.2015.10009 Abstract ( 486 )   [Full Text(HTML)] () PDF (2009KB) ( 133 )   Caenorhabditis elegans (C. elegans) has been widely used as a model organism for biomedical research due to its sufficient homology with human at molecular or genomic level. In this work, we describe a microfluidic device not only to investigate the response of C. elegans including lifespan and oxidative stress, but also to evaluate the protective effect of polydatin induced by high-glucose condition. It was found that the mean lifespan of worms was significantly reduced and the oxidative stress protein GST-4 was increased in worms that are subjected to high glucose. However, a certain dose of polydatin could weaken the increased oxidative stress induced by high-glucose and extend the lifespan, indicating the protective effect of polydatin against the toxic of high-glucose. The established approach is simple to operate, easy for realtime imaging and multiparatemer evaluations in parallel, providing a potential platform for drug evaluation/screening in a high throughput format at single animal resolution.

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Effects of carrier liquid and flow rate on the separation in gravitational field-flow fractionation GUO Shuang, ZHU Chenqi, YANG Yaya, QIU Bailing, WU Di, LIANG Qihui, HE Jiayuan, HAN Nanyin 2016, 34 (2):  146-151.  DOI: 10.3724/SP.J.1123.2015.08021 Abstract ( 464 )   [Full Text(HTML)] () PDF (1069KB) ( 97 )   Gravitational field-flow fractionation is the simplest field-flow fractionation technique in terms of principle and operation. The earth's gravity is its external field. Different sized particles are injected into a thin channel and carried by carrier fluid. The different velocities of the carrier liquid in different places results in a size-based separation. A gravitational field-flow fractionation (GrFFF) instrument was designed and constructed. Two kinds of polystyrene (PS) particles with different sizes (20 μ m and 6 μ m) were chosen as model particles. In this work, the separation of the sample was achieved by changing the concentration of NaN3, the percentage of mixed surfactant in the carrier liquid and the flow rate of carrier liquid. Six levels were set for each factor. The effects of these three factors on the retention ratio (R) and plate height (H) of the PS particles were investigated. It was found that R increased and H decreased with increasing particle size. On the other hand, the R and H increased with increasing flow rate. The R and H also increased with increasing NaN3 concentration. The reason was that the electrostatic repulsive force between the particles and the glass channel wall increased. The force allowed the samples approach closer to the channel wall. The results showed that the resolution and retention time can be improved by adjusting the experimental conditions. These results can provide important values to the further applications of GrFFF technique.

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Preparation and chromatographic performance of a silica-bonded (4-cyclopentadienyl benzoic acid-iron-toluene) hexafluorophosphoric acid stationary phase CAO Aijuan, LI Xiaole, QIAO Lijun, ZHOU Xiaohua, YU Ajuan, ZHANG Shusheng, WU Yangjie 2016, 34 (2):  152-157.  DOI: 10.3724/SP.J.1123.2015.08029 Abstract ( 454 )   [Full Text(HTML)] () PDF (971KB) ( 75 )   Based on the unique molecular structure of ferrocene and its potential as a new liquid chromatography separation medium, a new silica-bonded (4-cyclopentadienyl benzoic acid-iron-toluene) hexafluorophosphoric acid stationary phase was prepared. The structure of this new material was characterized by infrared spectroscopy, elemental analysis, thermogravimetric analysis et al. The chromatographic performance and retention mechanism of this new stationary phase were evaluated using different solute probes, including polycyclic aromatic hydrocarbons (PAHs), positional isomers of naphthylamine, positional isomers of nitro-aniline, nitroimidazoles, organic phosphorus et al. It could provide various action sites for different solutes in normal-phase chromatography such as π electron transfer, π-π electron interactions, dipole-dipole interactions, and electrostatic interactions with the substrates. And the possible separation mechanisms are discussed.

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Determination of 250 pesticide residues in vegetables using QuEChERS-ultra performance liquid chromatography-tandem mass spectrometry ZHANG Aizhi, WANG Quanlin, CAO Lili, LI Yu, SHEN Hao, SHEN Jian, ZHANG Shufen, MAN Zhengyin 2016, 34 (2):  158-164.  DOI: 10.3724/SP.J.1123.2015.09026 Abstract ( 772 )   [Full Text(HTML)] () PDF (868KB) ( 281 )   A multiresidue analytical method for the determination of 250 pesticide residues in vegetables was developed by using QuEChERS-ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The target compounds were extracted with acetonitrile containing 1%(v/v) acetic acid, purified by a mixed sorbent of MgSO4, primary secondary amine (PSA), graphitized carbon black (GCB) and C18, separated on a Waters ACQUITYTM UPLC BEH C18 column (100 mm×2.1 mm, 1.7 μ m) and detected by UPLC-MS/MS. Anhydrous magnesium sulfate was used as a dewatering agent. The effects of the amounts of MgSO4, PSA, GCB and C18 added on the recoveries of 250 pesticides were investigated. The results showed that the purification effect was best when 300 mg MgSO4, 200 mg PSA, 10 mg GCB and 100 mg C18 in 2 mL of the extract were added. For the 250 pesticide residues, the limits of detection (LODs) of the method were from 0.01 to 50.00 μ g/kg. The recoveries obtained ranged from 60.1% to 120% at three spiked levels in Chinese chives with the relative standard deviations between 3.5% and 19.5% using matrix matched external standard method. The results showed that the method is able to meet requirements of the multiresidue detection of the 250 pesticides in vegetable. The method has the advantages of rapidity, simplicity, high sensitivity and better purification effect. It is suitable for the rapid determination of the common pesticides in vegetables, and it provides a strong guarantee for the risk assessments of the quality and safety of vegetables.

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Dynamic behavior of aldicarb and its metabolites in cabbage by liquid chromatography-tandem mass spectrometry DING Kuiying, XU Wenjuan, LI Kai, GUO Liqiang, SUN Jun 2016, 34 (2):  165-169.  DOI: 10.3724/SP.J.1123.2015.08018 Abstract ( 493 )   [Full Text(HTML)] () PDF (843KB) ( 103 )   A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the study of dynamic behavior of aldicarb and its metabolite residues in cabbage. Aldicarb was applied onto cultivated cabbages. The pesticides concentrations were measured periodically (between application and harvest), and modeled to illustrate the dynamic behavior. The results showed that the liner ranges of aldicarb and its metabolites were from 0.005 to 0.2 mg/L, and the recoveries ranged from 78.9% to 108.5% with the relative standard deviations of 2.03%-8.91%(n=8). The aldicarb in cabbage increased at first with the first-order kinetic equation model of c=0.020e0.136t with the correlation coefficient (r2) of 0.888, and then decreased with the equation of c=0.65e-0.059t with the r2 of 0.979 and the half-life of 29.1 d. The reducing processes of aldicarb-sulfone and aldicarb-sulfoxide both matched the first-order kinetic equations (c=23.4e-0.044t and c=4.54e-0.027t) with r2 of 0.916 and 0.972 respectively. To meet the limitation requirement of 0.01 mg/kg, 70.7, 226.6 and 176.3 d were respectively necessary for aldicarb, aldicarb-sulfone and aldicarb-sulfoxide. Final residues of aldicarb-sulfone and aldicarb-sulfoxide were still more than the limitation requirements, indicating that aldicarb should not be used in vegetables of growth cycle shorter than 120 d. This study provided theoretical basis for dynamic behavior of aldicarb residue and its safe use in vegetables.

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Simultaneous determination of the residues of four β2-agonists in animal foods by modified high performance liquid chromatography-tandem mass spectrometry LI Juan, QIAO Qingdong, ZHUANG Jingxin, WANG Cuiping 2016, 34 (2):  170-175.  DOI: 10.3724/SP.J.1123.2015.08033 Abstract ( 452 )   [Full Text(HTML)] () PDF (1333KB) ( 117 )   An analytical method was developed to simultaneously determine the residues of four β2-agonists in animal foods by high performance liquid chromatography/electrospray-tandem mass spectrometry (HPLC-MS/MS). Samples were extracted with 5% (mass fraction) trichloracetic acid, and then cleaned up by two solid phase extraction cartridges (HLB and ProElut PXC). Quantification of the four β2-agonists was achieved by HPLC-MS/MS in multiple reaction monitoring (MRM) using internal standard method. The limits of detection (S/N=3) of clenbuterol, salbutamol, ractopamine and terbutaline were 0.05, 0.05, 0.05 and 0.2 μ g/kg, and the limits of quantification (S/N=10) were 0.25, 0.25, 0.1 and 0.5 μ g/kg, respectively. The average recoveries of the four β2-agonists spiked in blank samples at the spiked levels of 2.5, 5 and 10 μ g/kg were 90.3%-120.5% with the relative standard deviation (RSD) range of 1.60%-9.33%. The method is reliable, sensitive, good recovery and repeatability. It is suitable for the determination of the residues of the four β2-agonists in animal foods.

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Determination of 23 antibiotics and 3 β-agonists in livestock drinking water by ultra performance liquid chromatography-tandem mass spectrometry coupled with solid-phase extraction SHI Ao 2016, 34 (2):  176-183.  DOI: 10.3724/SP.J.1123.2015.09021 Abstract ( 643 )   [Full Text(HTML)] () PDF (910KB) ( 146 )   A method has been developed for the simultaneous determination of 23 antibiotics (four categories) and 3 β-agonists in livestock drinking water using solid-phase extraction and ultra performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (UPLC-ESI MS/MS). The samples were adjusted pH to 5.0, added Na2EDTA, enriched and cleaned-up by an HLB solid-phase extraction cartridge. The target compounds were confirmed and quantified by UPLC-ESI MS/MS with external standard method for the antibiotics and internal standard method for the β-agonists. The recoveries were assessed by using lab tap water as matrix. The average recoveries of the 23 antibiotics and the 3 β-agonists were in the range of 50.7%-104.6% and the relative standard deviations (RSDs) were 2.6%-8.8%(n=3). Under the optimal conditions, the calibration curves of the 23 antibiotics and the 3 β-agonists showed good linearity with the correlation coefficients better than 0.994. The limits of detection (LODs, S/N≥3) ranged from 0.01-0.20 ng/L. The developed method was applied to analyze the livestock drinking waters in 36 Beijing intensive livestock farms. The results showed that some antibiotics were detected.

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Determination of ginkgolic acids in the ginkgo biloba extract and its preparations by ultra high performance liquid chromatography-triple quadrupole mass spectrometry SUN Jian, LI Limin, HU Qing, MAO Xiuhong, JI Shen 2016, 34 (2):  184-188.  DOI: 10.3724/SP.J.1123.2015.08027 Abstract ( 510 )   [Full Text(HTML)] () PDF (828KB) ( 129 )   An analytical method was developed for the determination of ginkgolic acids in ginkgo biloba extract and its preparations by ultra high performance liquid chromatography-triple quadrupole mass spectrometry. A chromatographic column, Agilent Poroshell 120 EC-C18(50 mm×3.0 mm, 2.7 μ m), was used with methanol-1% acetic acid (90 : 10, v/v) as the mobile phase. The ginkgo acids were detected by electrospray ionization mass spectrometry in negative mode with multiple reaction monitoring (MRM) mode. Ginkgo acids C13 : 0, C15 : 1 and C17 : 1 possessed good linear correlations in the mass concentration range from 2 to 200 μ g/L, with the correlation coefficients more than 0.999. The mean recoveries at the spiked levels of 5, 20 and 100 μ g/L were in the range of 86.3%-114.3%, and the RSDs were 0.5%-13.6%. The limits of detection and quantification were 0.003-0.08 μ g/g and 0.01-0.19 μ g/g, respectively. The method was successfully applied to the analysis of actual samples.

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Determination of succinic acid in desvenlafaxine succinate by high performance ion-exclusion chromatography and high performance ion-exchange chromatography ZONG Yanping, LI Jinghua, SUN Wei, LIU Guixia, LU Jinghua, SHAN Guangzhi 2016, 34 (2):  189-193.  DOI: 10.3724/SP.J.1123.2015.08017 Abstract ( 672 )   [Full Text(HTML)] () PDF (830KB) ( 142 )   New methods were developed for the determination of succinic acid in desvenlafaxine succinate (DVS) by high performance ion-exclusion chromatography (HPIEC) and high performance ion-exchange chromatography (HPIC). HPIEC and HPIC methods were used separately to determinate the succinic acid in DVS. With HPIEC, the sample was diluted with 2.50×10-3mol/L sulfuric acid solution and filtrated by 0.22 μ m polyether sulfone filter membrane, and then analyzed by HPIEC directly without any further pretreatment. The analytical column was Phenomenex Rezex ROA-organic Acid H+(8%)(300 mm×7.8 mm). The mobile phase was 2.50×10-3mol/L sulfuric acid solution at the flow rate of 0.5 mL/min. The column temperature was set at 40 ℃, and the detection wavelength was 210 nm. The injection volume was 10 μ L. The assay was quantified by external standard method. With HPIC, the sample was diluted with ultrapure water and filtrated by 0.22 μ m polyether sulfone filter membrane, and then analyzed by HPIC directly without any further pretreatment. The analytical column was Dionex IonPac AS11-HC (250 mm×4 mm) with a guard column IonPacAG11-HC (50 mm×4 mm). Isocratic KOH elute generator was used at the flow rate of 1.0 mL/min. The detection was performed by a Dionex suppressed (DIONEX AERS 500 4-mm) conductivity detector. The injection volume was 10 μ L. The content computation was performed with peak area external reference method. The results of HPIEC method for succinic acid were 28.8%, 28.9% and 28.9%, while the results of HPIEC method were 28.2%, 28.6% and 28.6%. The results of HPIEC and HPIC methods were not significantly different. The two methods can both be used to determine the contents of succinic acid in DVS. The surveillance analytical method should be chosen according to the situation.

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Determination of 21 organophosphorus pesticides in tea by gas chromatography-mass spectrometry coupled with hydroxylated multi-walled carbon nanotubes based on dispersive solid-phase extraction RONG Jiefeng, WEI Hang, LI Yijun, HUANG Huoshui, XU Meizhu 2016, 34 (2):  194-201.  DOI: 10.3724/SP.J.1123.2015.07021 Abstract ( 674 )   [Full Text(HTML)] () PDF (2196KB) ( 186 )   A rapid determination method of 21 organophosphorus pesticides in tea was developed by QuEChERS method using modified multi-walled carbon nanotubes (MWCNTs-OH), primary-secondary amine (PSA) and MgSO4 coupled with gas chromatography-mass spectrometry. The pesticide residues in tea were extracted with a hexane-acetone (2 : 1, v/v) mixture, and cleaned up by dispersive solid-phase extraction using MWCNTs-OH and primary-secondary amine (PSA) as the sorbents. After centrifugation and filtration, the target compounds were analyzed by gas chromatography-mass spectrometry and quantified by the external standard method. Under the optimized conditions, good linearities were obtained in the range of 0.01-0.50 mg/kg. The average recoveries were in the range of 81.5%-109.4% at three spiked levels, with relative standard deviations (RSDs, n=5) of 2.3%-10.6%. The limits of quantification were 0.001-0.040 mg/kg. This method is simple, fast, sensitive, cheap, and can meet the requirements of the rapid detection of organophosphorus pesticides in tea.

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Determination of short-chain chlorinated paraffins in ambient air using high-volume sampling combined with high resolution gas chromatography-electron capture negative ion-low resolution mass spectrometry SHI Leimeng, GAO Yuan, HOU Xiaohong, ZHANG Haijun, Zhang Yichi, CHEN Jiping 2016, 34 (2):  202-208.  DOI: 10.3724/SP.J.1123.2015.08032 Abstract ( 552 )   [Full Text(HTML)] () PDF (1884KB) ( 102 )   An analytical method for quantifying short-chain chlorinated paraffins (SCCPs) in ambient air using high-volume sampling combined with high resolution gas chromatography-electron capture negative ion-low resolution mass spectrometry (HRGC-ECNI-LRMS) was developed. An acidified silica gel column and a basic alumina column were used to optimize the cleanup procedures. The results showed a good linearity (R2＞0.99) between the total response factors and the degree of chlorination of SCCPs in the content range of 58.1%-63.3%. The limits of detection (S/N≥3) and the limits of quantification (S/N≥10) were 4.2 and 12 pg, respectively. The method detection limit (MDL) for SCCPs was 0.34ng/m3 (n=7). The recoveries of SCCPs in air samples were in the range of 81.9% to 94.2%. It is demonstrated that the method is suitable for the quantitative analysis of SCCPs in air samples.

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Determination of volatile organic compounds in ambient air by thermal desorption-gas chromatography-triple quadrupole tandem mass spectrometry FENG Lili, HU Xiaofang, YU Xiaojuan, ZHANG Wenying 2016, 34 (2):  209-214.  DOI: 10.3724/SP.J.1123.2015.09023 Abstract ( 709 )   [Full Text(HTML)] () PDF (843KB) ( 171 )   A method was established for the simultaneous determination of 23 volatile organic compounds (VOCs) in ambient air with combination of thermal desorption (TD) and gas chromatography-triple quadrupole tandem mass spectrometry (GC-MS/MS). The air samples were collected by active sampling method using Tenax-TA sorbent tubes, and desorbed by thermal desorption. The analytes were determined by GC-MS/MS in selected reaction monitoring (SRM) mode, and internal standard method was applied to quantify the VOCs. The results of all the 23 VOCs showed good linearities in low level (0.01-1 ng) and high level (1-100 ng) with all the correlation coefficients (r2) more than 0.99. The method quantification limits were between 0.00008-1 μ g/m3. The method was validated by means of recovery experiments (n=6) at three spiked levels of 2, 10 and 50 ng. The recoveries between 77% and 124% were generally obtained. The relative standard deviations (RSDs) in all cases were lower than 20%, except for chlorobenzene at the low spiked level. The developed method was applied to determine VOCs in ambient air collected at three sites in Shanghai. Several compounds, like benzene, toluene, ethylbenzene, m-xylenes, p-xylenes, styrene, 1,2,4-trimethylbenzene and hexachlorobutadiene were detected and confirmed in all the samples analyzed. The method is highly accurate, reliable and sensitive for monitoring the VOCs in ambient air.

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Identification of isoparaffin components in petroleum middle fractions LIU Yingrong, JIANG Jingjie, LIU Zelong, TIAN Songbai 2016, 34 (2):  215-221.  DOI: 10.3724/SP.J.1123.2015.09006 Abstract ( 810 )   [Full Text(HTML)] () PDF (1384KB) ( 154 )   The identification of isoparaffin components in petroleum middle fractions including kerosene and diesel fuels was investigated by gas chromatography-mass spectrometry (GC/MS). The isodewaxing middle fraction and distilled diesel were selected as the objective samples for identification. It was shown that the isoparaffin components in middle fraction were well separated with their branched alkyl substituent numbers on a capillary chromatographic column in selected ion monitoring (SIM) mode of GC/MS. The identification for C10-C24 isoparaffins was realized with the technique of GC/MS, such as the fragmentation pathways of electron ionization and SIM technique, boiling point rule, published retention indices and theoretical rules about component retention behavior in GC including carbon number rule etc. Finally, the retention indices for the mono-substituted, di-substituted and multi-substituted isoparaffins from C10 to C24 were presented, which could provide an overall knowledge of isoparaffin distribution at carbon number level in fuels. Meanwhile, the peaks that could be well resolved in each isoparaffin group were also identified, and the detailed data for about 80 C10-C21 methyl-substituted isoparaffins and isoprenoid biomarkers were also given. The results showed that in isodewaxing middle fraction studied, the mono-substituted and di-substituted isoparaffins were the main paraffins, whereas in distilled diesel studies, the mono-substituted isoparaffins and isoprenoid biomarkers were the main ones.