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    Chinese Journal of Chromatography
    2015, Vol. 33, No. 11
    Online: 08 November 2015

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    Special Column on Preparation of Separation Media with Specific Selectivity
    Development of preparation of immobilized enzyme reactors in proteomics
    ZHANG Lingyi, WANG Bingbing, SHANGGUAN Lulu, ZHANG Runsheng, CHEN Jianhu, ZHANG Weibing
    2015, 33 (11):  1121-1125.  DOI: 10.3724/SP.J.1123.2015.06028
    Abstract ( 402 )   [Full Text(HTML)] () PDF (816KB) ( 216 )  

    As an important part in "bottom-up" strategy of proteomics, immobilized enzyme reactors have great significance in the development of fast and more efficient protein analytical method, owing to its advantages of high speed and enzymatic efficiency, good stability and activity, easy operation, and the possibility of hyphenating with multiple detection instruments. In this paper, the preparation methods of immobilized enzyme reactors and their applications in proteomic investigation are introduced, focusing on the nature of enzymes, the immobilization methods and the carrier materials used for immobilizing enzyme. In recent years, the investigations are focused on increasing the immobilization amounts of enzyme, keeping enzymatic activity, improving enzymatic efficiency and decreasing nonspecific adsorption. The investigation results showed that by using novel carriers such as nanomaterial and monolith, increasing of hydrophilicity of carrier and tandem hydrolysis with multiple enzymes can greatly improve the performance of immobilized enzyme reactors and increase protein identification efficiencies.

    Advances of poly(ionic liquid) materials in separation science
    LIU Cuicui, GUO Ting, SU Rina, GU Yuchen, DENG Qiliang
    2015, 33 (11):  1126-1133.  DOI: 10.3724/SP.J.1123.2015.07033
    Abstract ( 703 )   [Full Text(HTML)] () PDF (2221KB) ( 265 )  

    Ionic liquids, as novel ionization reagents, possess beneficial characteristics including good solubility, conductivity, thermal stability, biocompatibility, low volatility and non-flammability. Ionic liquids are attracting a mass of attention of analytical chemists. Poly(ionic liquid) materials have common performances of ionic liquids and polymers, and have been successfully applied in separation science area. In this paper, we discuss the interaction mechanisms between the poly(ionic liquid) materials and analytes including hydrophobic/hydrophilic interactions, hydrogen bond, ion exchange, π - π stacking and electrostatic interactions, and summarize the application advances of the poly(ionic liquid) materials in solid phase extraction, chromatographic separation and capillary electrophoresis. At last, we describe the future prospect of poly(ionic liquid) materials.

    Advances in cucurbituril bonded stationary phases for chromatographic separation
    QI Fenglian, XU Yudong, MENG Zihui, XUE Min, XU Zhibin, QIU Lili, CUI Kejian
    2015, 33 (11):  1134-1139.  DOI: 10.3724/SP.J.1123.2015.09005
    Abstract ( 324 )   [Full Text(HTML)] () PDF (1207KB) ( 143 )  

    Cucurbit[n]urils (CB[n]), a kind of host molecules of the fourth generation supramolecule followed crown ethers, cyclodextrins and calixarenes in supramolecular chemistry, are macrocyclic ligands and consist of several glycoluril units. Their special molecular recognition based on unique separation selectivity and stability have gained great interest in supramolecular chemistry and chromatography. Hereby, we give a review of research progresses of cucurbit[n]urils structural features, its homologues and derivatives and their applications in chromatographic stationary phase.

    State of art of mixed-mode stationary phase
    XU Jiwei, SUN Yuanshe, TANG Tao, XIA Mingzhu, LEI Wu, WANG Fengyun, LI Tong
    2015, 33 (11):  1140-1146.  DOI: 10.3724/SP.J.1123.2015.06025
    Abstract ( 525 )   [Full Text(HTML)] () PDF (918KB) ( 331 )  

    With the development of science and technology, more and more complex samples like peptides and proteins need to be separated. It is difficult to separate them by single mode chromatography. Due to the unique separation character of mixed-mode chromatography, the same separation performance can be obtained in mixed-mode chromatography in one separation as multidimensional chromatography. And some disadvantages of multidimensional chromatography can be avoided in mixed-mode chromatography, such as the complexity of the system, the poor compatibility of mobile phases and the long analytical time. More and more attention is devoted to the mixed-mode chromatography in recent years. The focus on the mixed-mode chromatography is to design new structures of mixed-mode stationary phase. At present, mixed-mode stationary phases included reversed-phase/ion-exchange, reversed-phase/hydrophilic, hydrophilic/ion-exchange, zwitterionic and trimode mixed-mode stationary phases. The kinds of mixed-mode stationary phases are summarized and their features and applications in different fields are discussed in this review.

    Advances on the development of detection methods for the phthalate esters in food
    LI Xiaomin, WANG Jing, ZHANG Qinghe, LI Hongmei
    2015, 33 (11):  1147-1154.  DOI: 10.3724/SP.J.1123.2015.06027
    Abstract ( 605 )   [Full Text(HTML)] () PDF (885KB) ( 209 )  

    Phthalate esters are most widely used as plasticizers which have toxicity and carcinogenicity. Phthalate esters are found as contaminants in many food products and they are a branch of compounds, homologues and isomers, which present similar structures and properties. And the residue contents vary a lot in different matrices. Efficient sample pretreatment, highly selective separation mode, sensitive detection methods as well as reducing background interference are challenges for their determination in complex samples. In this paper, some sample pretreatment methods such as liquid-liquid extraction, liquid-liquid micro-extraction, solid phase extraction, solid phase micro-extraction, matrix solid-phase extraction and other traditional and new types of extraction and purification technology applied in the food samples are reviewed. The characteristics of analytical methods including gas chromatography, liquid chromatography, tandem mass spectrometry, high resolution mass spectrometry, enzyme-linked immunoassay, and ion mobility spectrometry are also discussed.

    Articles
    A novel multiple-channel apparatus for packing capillary chromatographic column and its application
    LV Yayao, HAO Feiran, WANG Huanhuan, FU Bin, QIAN Xiaohong, ZHANG Yangjun
    2015, 33 (11):  1155-1162.  DOI: 10.3724/SP.J.1123.2015.06021
    Abstract ( 401 )   [Full Text(HTML)] () PDF (1576KB) ( 122 )  

    A novel multiple-channel apparatus for packing capillary chromatographic column was designed and manufactured for packing six capillary chromatographic columns with close column efficiency at the same time. Briefly, it consists of a magnetic stirrer, a liquid chromatographic pump and a multiple-channel can. The reagents used for preparing ODS (C18) slurry and stirring condition of the magnetic stirrer were optimized in the study. Two batches of capillary chromatographic columns were packed under the optimum condition, and these packed capillary chromatographic columns were evaluated in the terms of peak capacity, sequence coverage, retention times of three peptide ions and column pressure using the tryptic digest of a bovine serum albumin (BSA) and detected by LC-MS in electrospray ionization (ESI) mode. The experimental results showed that the six capillary chromatographic columns packed at the same time had close column efficiencies, however, the column efficiencies of twelve capillary chromatographic columns packed at two times were significantly different. In addition, there was no significant column efficiency difference when packing one or six capillary chromatographic columns at the same time. The multiple-channel apparatus designed by us is simple, time-saving, and can be applied to pack capillary chromatographic columns with similar column efficiencies, thus it is of evident advantage over traditional one-channel apparatus.

    Determination of nine estrogenic steroids in milk using matrix solid phase dispersion-ultra performance liquid chromatography with mass spectrometric detector
    LIU Hongcheng, LI Ning, LIN Tao, SHAO Jinliang, LI Qiwan
    2015, 33 (11):  1163-1168.  DOI: 10.3724/SP.J.1123.2015.06035
    Abstract ( 393 )   [Full Text(HTML)] () PDF (1025KB) ( 106 )  

    An analytical method for the multiresidue determination of nine estrogenic steroids in milk was developed by modified matrix solid phase dispersion (MSPD) purification and ultra performance liquid chromatography (UPLC) with mass spectrometric detector (MSD). The sensitivity and accuracy of MSD were better than that of ultraviolet detector. In comparison with traditional mass spectrometry, the merits of MSD were simpler in operation and shorter in starting time (5 min). The results showed that the limits of detection of the compounds with nucleophilic substitution were high in positive ion mode of MSD and were easily affected by environmental conditions. The matrix effects of milk samples reduced from 84%-160% to 80%-121% after MSPD purification. The intraday precision and interday precision of the nine estrogenic steroids were 0.87%-1.78% and 1.82%-3.79%, respectively. The average recoveries were 68.7%-94.7%, and the relative standard deviations (RSDs) were less than 10%. The limits of detection (LODs) were 0.5-10 μ g/kg. The limits of quantification (LOQ) were 2-20 μ g/kg.

    Determination of amantadine and rimantadine residues in egg and chicken samples by dispersive solid phase extraction purification-ultra high performance liquid chromatography-tandem mass spectrometry
    LIN Tao, FAN Jianlin, LIU Xingyong, CHEN Xinglian, LI Yangang, LIU Hongcheng
    2015, 33 (11):  1169-1174.  DOI: 10.3724/SP.J.1123.2015.08010
    Abstract ( 604 )   [Full Text(HTML)] () PDF (867KB) ( 118 )  

    A method was developed for the determination of residual amantadine and rimantadine in eggs and chickens by dispersive solid phase extraction-ultra high performance liquid chromatography-tandem mass spectrometry. Egg and chicken samples were extracted with ammonia water-acetonitrile (2 : 98, v/v). The extraction solution was dried to 1 mL under nitrogen, and then purified by dispersive solid phase extraction method with C18 and NH2 sorbents. After purification, the extraction solution was filtered through a filter. The target compounds were analyzed by ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) on a ZORBAX C18 column using a mixture of 1 mmol/L ammonium acetate solution (containing 0.1% (v/v) formic acid) and methanol as mobile phases with gradient elution. The mass spectrometer was operated under multiple reaction monitoring (MRM) mode in positive mode. The good linearities were obtained for amantadine and rimantadine at a concentration range of 0.15-10.0 μ g/L. The limits of detection for amantadine and rimantadine were all 0.05 μ g/kg, and the limits of quantification were 0.20 μ g/kg. The recoveries of amantadine and rimantadine in eggs and chickens at three spiked levels (0.2, 1.0 and 2.0 μ g/kg) were in the range of 89%-108% with the relative standard deviations of 5.0%-8.6%. The results demonstrated that the method is suitable for the determination of amantadine and rimantadine in eggs and chickens.

    Determination of 213 pesticide residues in milk and milk power by gas chromatography-triple quadrupole tandem mass spectrometry
    WANG Jing, AI Lianfeng, MA Yusong, ZHANG Haichao, LI Wei, YU Meng
    2015, 33 (11):  1175-1185.  DOI: 10.3724/SP.J.1123.2015.07012
    Abstract ( 712 )   [Full Text(HTML)] () PDF (910KB) ( 155 )  

    On the basis of the optimization of solid phase extraction adsorbent, eluting solvent types and amounts, a gas chromatography-triple quadrupole tandem mass spectrometry (GC-MS/MS) method was established for the determination of 213 pesticide residues in milk and milk power. The samples were extracted by acetonitrile, cleaned-up with an ENVI-Carb/NH2 solid-phase extractant, and determined by GC-MS/MS using external standard method. The linear ranges were from 10 to 1000 μ g/L for 197 pesticides, from 50 to 1000 μ g/L for the other 16 pesticides with the correlation coefficients higher than 0.99. The limits of detection (LODs, S/N=3) varied over the range of 0.03 to 7.59 μ g/kg, and limits of quantification (LOQs, S/N=10) ranged from 0.10 to 21.94 μ g/kg. The average recoveries in different matrices were in the range of 66.9%-120.1% with the relative standard deviations (RSDs) of 1.23%-17.6%. This method is simple, rapid, sensitive and reliable for meeting the requirements for the simultaneous identification and quantification of the multi-residues in milk and milk power.

    Determination of three organophosphate ester flame retardants in baby carriages by gas chromatography-mass spectrometry combined with solid phase extraction
    LAI Xiaofang, FENG Anhong, XING Yuanna, YE Linquan, LIN Zhihui, CHEN Zeyong
    2015, 33 (11):  1186-1191.  DOI: 10.3724/SP.J.1123.2015.05019
    Abstract ( 537 )   [Full Text(HTML)] () PDF (844KB) ( 161 )  

    Organophosphate esters (OPEs) are high-production-volume chemicals used as flame retardants. Some western countries (e. g. America and European Union) have imposed restrictions on OPEs in baby products due to their similar persistent-organic-pollutants (POPs) properties. So far, there is no domestic or foreign standard for OPEs flame retardants in baby carriages. Ultrasonic extraction was used to extract three OPEs from baby carriages, and the extracts were purified by a florisil solid phase extraction (SPE) column, and finally detected by gas chromatography-mass spectrometry (GC-MS). The spiked recoveries of the three OPEs were in the range of 89.5% to 107.3%. The limits of detection (3S/N) were 0.01 mg/kg, and the limits of quantification (10S/N) were 0.1 mg/kg. This method could eliminate matrix effects and give accurate qualitative analytical results for the three OPE flame retardants in baby carriages. Thirty-seven samples were analyzed and the tris(2-chloro-1-methylethyl) phosphate (TCPP) detection rate was up to 81.1% with the mass concentration range of 1.0-15312.8 mg/kg, and 32.4% of the samples exceeded the European Union directive(2014/79/EU)for TCPP(> 5 mg/kg), as well as tris(2-chloroethyl) phosphate (TCEP) and tris[2-chloro-1-(chloromethyl)ethyl]phosphate(TDCP) in two samples, which were in the range of 6.2-44.1 mg/kg. Thus, relatively high OPEs flame retardants risk was presented in baby carriages.

    Determination of the solubility parameter of ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate by inverse gas chromatography
    MA Xiaohong, WANG Qiang, LI Xiaoping, TANG Jun, ZHANG Zhengfang
    2015, 33 (11):  1192-1198.  DOI: 10.3724/SP.J.1123.2015.04041
    Abstract ( 743 )   [Full Text(HTML)] () PDF (890KB) ( 173 )  

    Thermodynamic properties of ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4) were determined via inverse gas chromatography (IGC). Two groups of solvents with different chemical natures and polarities were used to obtain information about [BMIM]BF4-solvent interactions. The specific retention volume, molar heat of sorption, weight fraction activity coefficient, Flory-Huggins interaction parameter as well as solubility parameter were also determined in a temperature range of 333-373 K. The results showed that the selected solvents n-C10 to n-C12, carbon tetrachloride, cyclohexane and toluene were poor solvents for [BMIM]BF4, while dichloromethane, acetone, chloroform, methyl acetate, ethanol and methanol were favorite solvents for [BMIM]BF4. In addition, the solubility parameter of [BMIM]BF4 was determined as 23.39 (J/cm3)0.5 by the extrapolation at 298 K. The experiment proved that IGC was a simple and accurate method to obtain the thermodynamic properties of ionic liquids. This study could be used as a reference to the application and research of the ionic liquids.

    Technical Notes
    Determination of six anticoccidials in chicken using QuEChERS combined with ultra high liquid chromatography-high resolution mass spectrometry
    MUHAREM Muhteber, YAN Hua, XU Shan, FENG Nan, HAO Jie, ZHU Chenqi, GUO Shuang, ZHANG Zhaohui, HAN Nanyin
    2015, 33 (11):  1199-1204.  DOI: 10.3724/SP.J.1123.2015.06016
    Abstract ( 435 )   [Full Text(HTML)] () PDF (1596KB) ( 149 )  

    An ultra high liquid chromatography-Q Exactive orbitrap mass spectrometry multi-residue method has been developed for the determination of six anticoccidials residues (dinitlmide, nicarbazin, diclazuril, toltrazuril, monensin and salinomycin) in chicken tissue. Sample preparation was based on QuEChERS method, using 1% (v/v) trichloroacetic acid/acetonitrile aqueous solution (3 : 7, v/v) as the extraction solvent and salting-out with sodium chloride followed by clean-up with 50 mg/mL primary secondary amine (PSA)+50 mg/mL neutral alumina (Alumina-N) dispersive solid phase extraction (DSPE). The separation of the compounds in liquid chromatography was carried out using a Waters Acquity UPLC® BEH C8 column (100 mm×2.1 mm, 1.7 μ m) with mobile phases consisting of methanol-5 mmol/L ammonium acetate aqueous solution in gradient elution. The Q Exactive orbitrap mass spectrometric detection was carried out with positive and negative electrospray ionization simultaneously. The results showed the linear ranges of the six target compounds were as follows: dinitolmide, 1.0-30.0 μ g/L; nicarbazin, 0.2-6.0 μ g/L; diclazuril and toltrazuril, 2.0-60.0 μ g/L; monensin and salinomycin, 4.0-120.0 μ g/L. The external standard method was used for quantification. The spiked recoveries at three levels for the six anticoccidials ranged from 67.7% to 126.8%. The relative standard deviations (RSDs) were ≤10.4%. The limits of quantification (LOQs) were as follows: dinitolmide, 2.50 μ g/kg; nicarbazin, 0.50 μ g/kg; diclazuril and toltrazuril, 5.00 μ g/kg; monensin and salinomycin, 20.00 μ g/kg. The developed method is easy of operation and of high sensitivity. It can meet the requirements of daily inspection.

    Determination of imidaclothiz in tea by QuEChERS cleanup and liquid chromatography-tandem mass spectrometry
    LIU Songnan, ZHAO Xinying, DONG Xiaoqian, XU Wenwen, ZHAO Rong
    2015, 33 (11):  1205-1209.  DOI: 10.3724/SP.J.1123.2015.07006
    Abstract ( 464 )   [Full Text(HTML)] () PDF (1269KB) ( 171 )  

    The method for the determination of imidaclothiz residue in tea by liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been developed. The imidaclothiz in tea was extracted by acetonitrile and purified by QuEChERS with PSA (primary secondary amine), C18, GCB (graphitized carbon black) as the adsorbents. The purified solution was centrifuged and the supernatant was diluted with water of equal volume. The separation was performed on a C18 column with a gradient elution program of acetonitrile (containing 0.1% (v/v) formic acid) and water at a flow rate of 0.30 mL/min. The mass spectrometer was carried out with electrospray ion source in the positive mode (ESI+) and selective reaction monitoring (SRM), quantified by external standard solution. The results showed that the mass concentration of imidaclothiz in the range of 1 to 500 μ g/L was linearly correlated with the peak area, and the correlation coefficient (r) was 0.9999. The limit of quantification (LOQ, S/N≥10) was 0.01 mg/kg. The recoveries in oolong tea and green tea at three spiked levels (0.01, 0.3 and 3 mg/kg) varied from 87.0%-101.0% and the relative standard deviations (RSDs, n=7) were between 2.1% and 13.1%. The real sample tests showed that the method is simple, cheap, accurate, specific, rapid, and suitable for the qualitative and quantitative confirmation of imidaclothiz residue in tea.

    Simultaneous determination of four drugs for kidney diseases in urine by high performance liquid chromatography
    LI Jing, GUO Zhanchen, ZHAO Xu, MA Yuhua, HAN Ping, FENG Shun
    2015, 33 (11):  1210-1213.  DOI: 10.3724/SP.J.1123.2015.07022
    Abstract ( 473 )   [Full Text(HTML)] () PDF (818KB) ( 75 )  

    A high performance liquid chromatographic (HPLC) method was proposed for the simultaneous determination of four drugs for kidney disease, enalapril, triamterene, furosemide and valsartan. After proteins being removed by acetone precipitation method, freeze drying and redissolving in mobile phase, the urine samples were analyzed by HPLC. Chromatographic separation was performed on a WondaSil C18-WR (150 mm×4.6 mm, 5 μ m) in gradient elution mode using 10.0 mmol/L ammonium acetate aqueous solution (pH 3.90) and acetonitrile as mobile phases at a flow rate of 1.0 mL/min. The detection wavelength was set at 254 nm. Under the optimized conditions, good linearities were obtained in the range of 0.15-300 mg/L, 0.05-100 mg/L, 0.75-750 mg/L, 0.05-100 mg/L, and the detection limits were 1.38×10-2, 7.67×10-3, 3.69×10-2, 1.16×10-2mg/L for enalapril, triamterene, furosemide and valsartan, respectively. The recoveries were in the range of 89.49%-99.20% with the relative standard deviations (RSDs) among 4.12%-9.44%. The method is simple, accurate and effective, and the results showed the method is applicable for the analysis of the four drugs for kidney diseases in real urine samples.

    Determination of docosahexaenoic acid in milk powder by gas chromatography using acid hydrolysis
    SHAO Shiping, XIANG Dapeng, LI Shuang, XI Xinglin, CHEN Wenrui
    2015, 33 (11):  1214-1218.  DOI: 10.3724/SP.J.1123.2015.06022
    Abstract ( 399 )   [Full Text(HTML)] () PDF (799KB) ( 108 )  

    A method to determine docosahexenoic acid (DHA) in milk powder by gas chromatography was established. The milk powder samples were hydrolyzed with hydrochloric acid, extracted to get total fatty acids by Soxhlet extractor, then esterified with potassium hydroxide methanol solution to form methyl esters, and treated with sodium hydrogen sulfate. The optimal experiment conditions were obtained from orthogonal experiment L9(33) which performed with three factors and three levels, and it requires the reaction performed with 1 mol/L potassium hydroxide solution at 25 ℃ for 5 min. The derivative treated with sodium hydrogen sulfate was separated on a column of SP-2560 (100 m×0.25mm×0.20 μ m), and determined in 55 min by temperature programming-gas chromatography. Good linearity was obtained in the range 5.0-300 mg/L with the correlation coefficient of 0.9999. The relative standard deviations (RSDs) were 3.4%, 1.2% and 1.1% for the seven repeated experiments of 10, 50 and 100 mg/L of DHA, respectively. The limit of detection was 2 mg/kg, and the recoveries of DHA were in the range of 90.4%-93.5%. The results are satisfactory through the tests of practical samples.