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    Chinese Journal of Chromatography
    2012, Vol. 30, No. 09
    Online: 28 September 2012

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    Articles
    A new peptide retention time prediction method for mass spectrometry based proteomic analysis by a serial and parallel support vector machine model
    Ji-yang ZHANG Dai-bing ZHANG Wei ZHANG Hong-wei XIE
    2012, 30 (09):  857-863.  DOI: 10.3724/SP.J.1123.2012.06021
    Abstract ( 1657 )   [Full Text(HTML)] () PDF (2392KB) ( 464 )  
    The online reversed-phase liquid chromatography (RPLC) contributes a lot for the large scale mass spectrometry based protein identification in proteomics. Retention time (RT) as an important evidence can be used to distinguish the false positive/true positive peptide identifications. Because of the nonlinear concentration curve of organic phase in the whole range of run time and the interactions among peptides, the sequence based RT prediction of peptides has low accuracy and is difficult to generalize in practice, and thus is less effective in the validation of peptide identifications. A serial and parallel support vector machine (SP-SVM) method was proposed to characterize the nonlinear effect of organic phase concentration and the interactions among peptides. The SP-SVM contains a support vector regression (SVR) only for model training (named as p-SVR) and 4 SVM models (named as C-SVM, l-SVR, s-SVR and n-SVR) for the RT prediction. After distinguishing the peptide chromatographic behavior by C-SVM, l-SVR and s-SVR were used to predict the peptide RT specifically to improve the accuracy. Then the peptide RT was normalized by n-SVR to characterize the peptide interactions. The prediction accuracy was improved significantly by applying this method to the processing of the complex sample dataset. The coefficient of the determination between predictive and experimental RTs reaches 0.95, the prediction error range was less than 20% of the total LC run time for more than 95% cases, and less than 10% of the total LC run time for more than 70% cases. The performance of this model reaches the best of known so far. More important, the SP-SVM method provides a framework to take into account the interactions among peptides in chromatographic separation, and its performance can be improved further by introducing new data processing and experiment strategy.
    Plasma fatty acid metabolic profiles for traditional Chinese medicine syndrome differentiation in diabetic patients using uncorrelated linear discriminant analysis
    XU Wenjuan1, ZHANG Liangxiao1, HUANG Yuhong2, YANG Qianxu1, XIAO Hongbin1*, ZHANG Deqin2*
    2012, 30 (09):  864-869.  DOI: 10.3724/SP.J.1123.2012.04033
    Abstract ( 1650 )   [Full Text(HTML)] () PDF (1089KB) ( 472 )  
    Diabetes is a common metabolic syndrome which presents a serious threat to human health. Traditional Chinese medicine (TCM) has been widely paid attention to its advantages and characteristics in the diagnosis and the treatment of diabetes. A strategy of classifying five TCM syndromes in diabetes (Qi-deficiency, Yin-deficiency, Qi- and Yin-deficiency, Damp heat and Blood stasis) was employed based on plasma fatty acid metabolic profiles, lipid metabolism indicators and chemometrics methods. Using orthogonal signal correction-partial least squares (OSC-PLS) method, the five syndromes were obviously distinguished from those of the health control, which confirmed there existed metabolite differences in different traditional Chinese medicine syndromes. Furthermore, a new method, uncorrelated linear discriminant analysis (ULDA), was applied in the discrimination of health control, TCM deficiency syndromes (Qi-deficiency, Yin-deficiency, Qi- and Yin-deficiency) and TCM empirical syndromes (Damp heat, Blood stasis), which demonstrated better clustering results, the correct rate reached 95.7%. The four potential biomarkers, C20:2, C20:5, triglycerides (TG) and high density lipoprotein (HDL), performed large contributions to the classification which can provide important information assisting TCM clinical diagnosis.
    Simultaneous determination of 11 aminophenols in hair dyes by high performance liquid chromatography
    ZHU Weixia1, WANG Caijuan2, YANG Jizhou1*, WEI Wei1, SUN Zhuanlian1, ZHANG Shusheng2
    2012, 30 (09):  870-875.  DOI: 10.3724/SP.J.1123.2012.04014
    Abstract ( 2061 )   [Full Text(HTML)] () PDF (948KB) ( 535 )  
    An analytical method was developed for the simultaneous determination of 11 aminophenols in direct and oxidized hair dyes by high performance liquid chromatography (HPLC). The samples were extracted with methanol using sodium bisulfite for anti-oxidation. The purification was carried out with the high speed frozen centrifugation. The separation was performed on an Agilent Zorbax SB C18 column with the mobile phases of acetonitrile and an ion pair system of sodium heptanesulfonate and phosphate under a gradient elution. The analytes were detected at three different wavelengths of 230, 270 and 400 nm. In the concentration range of 0.05~500 mg/L, the correlation coefficients for the 11 aminophenols were not less than 0.9992. The limits of quantification including 4-amino-3-nitrophenol, 2-amino-5-nitrophenol, and 4-(2-hydroxyethyl)amino-3-nitrophenol were 5 mg/kg. Other aminophenols including 4-aminophenol, 4-methyl aminophenol, 3-aminophenol, 2-aminophenol, 5-amino-o-cresol, 4-amino-3-methylphenol, 5-(2-hydroxyethyl)amino-o-cresol and 2-amino-4-nitrophenol were 20 mg/kg. The recoveries of the aminophenols spiked at different levels ranged from 88.5% to 109.5% with the relative standard deviations (RSDs) within the range of 2.2%~8.3%. The commercially available hair dye samples were analyzed for the aminophenols and the results showed that the method was suitable for the determination of the 11 aminophenols in direct and oxidized hair dyes.
    Triacylglyceride profiling in serum by silver ion high performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry
    YANG Qin, SHI Xianzhe*, SHAN Yuanhong, DOU Abo, XU Guowang
    2012, 30 (09):  876-882.  DOI: 10.3724/SP.J.1123.2012.05021
    Abstract ( 1903 )   [Full Text(HTML)] () PDF (1006KB) ( 521 )  
    A simple and effective method was developed to investigate triacylglyceride (TAG) compounds in biological matrices using silver ion high performance liquid chromatography-mass spectrometry (Ag+-HPLC-MS). The TAG compounds from mouse serum were extracted by a modified Folch method using the classical CHCl3-MeOH solvent system. The extract was separated on a Varian ChromSpher 5 Lipids column with isocratic elution using acetonitrile-hexane (1:99, v/v) as mobile phase at a flow rate of 0.75 mL/min, and detected by a mass spectrometer equipped with an atmospheric pressure chemical ionization (APCI) source in positive ion mode to acquire sufficient MS information of TAG compounds by enhanced mass spectrometry (EMS), enhanced product ion (EPI) and neutral loss (NL) scans. The identification of TAG compounds was based on their chromatographic behaviors and MS data. Besides, the NL scans of thirty fatty acids were performed to further validate the results. Finally, 66 TAG compounds as well as 5 cholesteryl ether (CE) compounds were obtained from the mouse serum extract. This method is simple, reproducible and also suitable for the analysis of TAG compounds in other samples.
    Simultaneous extraction and determination of nine chemically synthetic anticoccidial drug multi-residues in chicken meat using high performance liquid chromatography-tandem mass spectrometry
    SHI Zuhao1, ZHANG Xiaoyan1,2, BU Shijin2, CHEN Dawei1, PU Junhua1, GAO Yushi1*, TANG Xiujun1
    2012, 30 (09):  883-888.  DOI: 10.3724/SP.J.1123.2012.05023
    Abstract ( 1534 )   [Full Text(HTML)] () PDF (1246KB) ( 522 )  
    A high performance liquid chromatography-tandem mass spectrometric (HPLC-MS/MS) method was developed for the simultaneous extraction and determination of multi-residues of nine chemically synthetic anticoccidial drugs in chicken meat. Toltrazuril-D3 was used as the internal standard. The sample was extracted by 15 mL acetonitrile/dimethyl sulfoxide (4:1, v/v, containing 2% acetic acid), cleaned-up by a QuEChERS (quick, easy, cheap, effective, rugged and safe) clean-up tube with 150 mg octadecylsilyl (ODS), 100 mg Florisil and 100 mg graphitized carbon black (GCB). After the concentration, the extract was analyzed by HPLC-MS/MS. The results showed that good linearity in the range of 20~150 μg/L for each target compound. The recoveries were between 81.5% and 103.6% with the relative standard deviations lower than 15%. The method is simple, rapid, and suitable to detect the chemically synthetic anticoccidial drug residues with high throughput.
    Determination of eight pesticide residues in tea by liquid chromatography-tandem mass spectrometry and its uncertainty evaluation
    HU Beizhen1*, CAI Haijiang2, SONG Weihua1
    2012, 30 (09):  889-895.  DOI: 10.3724/SP.J.1123.2012.04024
    Abstract ( 1684 )   [Full Text(HTML)] () PDF (1120KB) ( 567 )  
    A method was developed for the determination of eight pesticide residues (fipronil, imidacloprid, acetamiprid, buprofezin, triadimefon, triadimenol, profenofos, pyridaben) in tea by liquid chromatography-tandem mass spectrometry. The sample was extracted by accelerated solvent extraction with acetone-dichloromethane (1:1, v/v) as solvent, and the extract was then cleaned-up with a Carb/NH2 solid phase extraction (SPE) column. The separation was performed on a Hypersil Gold C18 column (150 mm×2.1 mm, 5 μm) and with the gradient elution of acetonitrile and 0.1% formic acid. The eight pesticides were determined in the modes of electrospray ionization (ESI) and multiple reaction monitoring (MRM). The analytes were quantified by matrix-matched internal standard method for imidacloprid and acetamiprid, by matrix-matched external standard method for the other pesticides. The calibration curves showed good linearity in 1~100 μg/L for fipronil, and in 5~200 μg/L for the other pesticides. The limits of quantification (LOQs, S/N>10) were 2 μg/kg for fipronil and 10 μg/kg for the other pesticides. The average recoveries ranged from 75.5% to 115.0% with the relative standard deviations of 2.7%~7.7% at the spiked levels of 2, 5, 50 μg/kg for fipronil and 10, 50, 100 μg/kg for the other pesticides. The uncertainty evaluation for the results was carried out according to JJF 1059-1999 “Evaluation and Expression of Uncertainty in Measurement”. Items constituting measurement uncertainty involved standard solution, weighing of sample, sample pre-treatment, and the measurement repeatability of the equipment were evaluated. The results showed that the measurement uncertainty is mainly due to sample pre-treatment, standard curves and measurement repeatability of the equipment. The method developed is suitable for the conformation and quantification of the pesticides in tea.
    Determination of fungicide anilinopyrimidine residues in food by series solid phase extraction-high performance liquid chromatography-tandem mass spectrometry
    CHEN Dajie1,2, ZHANG Zhigang1, ZHOU Yu1, XIAO Zongyuan2, XU Dunming1*
    2012, 30 (09):  896-902.  DOI: 10.3724/SP.J.1123.2012.05003
    Abstract ( 1810 )   [Full Text(HTML)] () PDF (1360KB) ( 360 )  
    A high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was established for the determination of fungicide anilinopyrimidine residues including pyrimethanil, mepanipyrim, and cyprodinil in foodstuffs with series solid phase extraction (SPE). The food sample was first extracted with ethyl acetate, and then purified by an ENVI-Carb cartridge and a Florisil SPE cartridge. The analytes were determined by HPLC-MS/MS and quantified by external standard method. The mass spectrometric detection was operated with electrospray in positive ionization mode and the fungicide anilinopyrimidines were identified in multiple reaction monitoring (MRM) mode. The linear range of the method was 1~20 μg/L, with the correlation coefficient (r2) over 0.9990. The transitions of the precursor ions to two selected product ions were involved, in which one group for quantification were m/z 200.1/107.1 for pyrimethanil, m/z 224.0/106.0 for mepanipyrim and m/z 226.0/108.1 for cyprodinil, and the other group for identification were m/z 200.1/183.1 for pyrimethanil, m/z 224.0/131.1 for mepanipyrim and m/z 226.0/133.1 for cyprodinil, respectively. No significant matrix effect was found for spiked samples after the purification. The recoveries of the fungicide anilinopyrimidines spiked in food samples were 73.2%~98.7% at the spiked levels of 0.1, 0.5, 1.0 μg/kg. The relative standard deviations (RSDs) were less than 10%. The limits of detection (LODs) and limits of quantification (LOQs) were 0.03 μg/kg and 0.1 μg/kg for the three fungicides, respectively. The results showed that the proposed method is sensitive and accurate for the determination of fungicide anilinopyrimidines in foodstuffs. The method should be applicable for routine analysis of pyrimethanil, mepanipyrim, cyprodinil residues in foodstuffs.
    Direct determination of ethyl carbamate in Chinese rice wine and grape wine by ultra performance liquid chromatography-electrospray ionization tandem mass spectrometry
    WANG Lijuan1, KE Runhui1,2*, WANG Bing3, YIN Jianjun1,2, SONG Quanhou1,2
    2012, 30 (09):  903-907.  DOI: 10.3724/SP.J.1123.2012.05007
    Abstract ( 2122 )   [Full Text(HTML)] () PDF (912KB) ( 437 )  
    An ultra performance liquid chromatography-electrospray ionization tandem mass spectrometric (UPLC-ESI-MS/MS) method was established for the direct determination of ethyl carbamate in Chinese rice wine and grape wine. The Chinese rice wine and grape wine samples were diluted with distilled water, filtered through 0.22 μm microporous membrane. The LC separation was performed on a Waters Acquity UPLC system with a BEH C18 column, acetonitrile and 0.1% (v/v) acetic acid aqueous solution as the mobile phase. The ethyl carbamate was determined in the mode of electrospray positive ionization (ESI+) and multiple reaction monitoring (MRM). The butyl carbamate (BC) was used as the internal standard for the quantitative determination. The calibration curve showed good linearity in the range of 2~500 μg/L with the correlation coefficient greater than 0.995. The limit of detection (LOD) was 1.7 μg/L and the limit of quantification (LOQ) was 5.0 μg/L. The recoveries of the ethyl carbamate in Chinese rice wine and grape wine was in the range of 90%~102%. The relative standard deviations (RSDs) of intra-day and inter-day determinations were 0.8%~4.5% and 1.4%~5.6% (n=6). The results indicated that the proposed method is easy, fast, sensitive, and suitable for the determination of ethyl carbamate in Chinese rice wine and grape wine.
    Simultaneous determination of 29 veterinary drugs in compound feeds by ultra performance liquid chromatography-electrospray ionization tandem quadrupole mass spectrometry
    ZHAO Ying*, LIU Yu, JIN Yan, XU Yihong, ZHONG Yu, JIANG Shi, LI Xiaodong, ZENG Fan, ZHOU Jiannan
    2012, 30 (09):  908-914.  DOI: 10.3724/SP.J.1123.2012.06019
    Abstract ( 1486 )   [Full Text(HTML)] () PDF (1119KB) ( 435 )  
    An ultra performance liquid chromatography with electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS) method was developed for the simultaneous determination of 29 veterinary drugs of quinolones, sulfonamides, macrolides and nitrofurans in compound feeds. The sample was extracted with methanol-acetonitrile (1:1, v/v), and then cleaned up using solid phase extraction with an Oasis HLB column, detected by UPLC-ESI-MS/MS. The UPLC separation was performed on a C18 column (100 mm×2.1 mm, 1.7 μm) using a gradient elution with the mobile phases of methanol and 0.1% (v/v) formic acid aqueous solution. The ESI-MS/MS detection was achieved in positive mode under multiple reaction monitoring (MRM) mode. The linear ranges were from 0.01 to 5.0 mg/L with the correlation coefficients above 0.99 for all the 29 veterinary drugs. The average recoveries of the 29 veterinary drugs spiked in three feed matrixes (the compound premix feed, the complete formula feed and the concentrated feed) at four spiked levels were 61.2%~94.3% with the relative standard deviations (RSDs) of 2.2%~15.0%. The limits of detection were 0.01 mg/kg or 0.05 mg/kg. The method is rapid, accurate, reproducible, sensitive and easy to apply, and suitable for the simultaneous determination of diverse veterinary drugs in compound feeds.
    Preparation and certification of mussel reference material for organochlorine pesticides and polychlorinated biphenyls using isotope dilution-high resolution mass spectrometry
    LU Xianbo, CHEN Jiping*, WANG Shuqiu, ZOU Lili, TIAN Yuzeng, NI Yuwen, SU Fan
    2012, 30 (09):  915-921.  DOI: 10.3724/SP.J.1123.2012.04035
    Abstract ( 1702 )   [Full Text(HTML)] () PDF (1278KB) ( 443 )  
    A method for the preparation and certification of the reference material of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in mussel tissue is described. The mussel tissue from Dalian Bay was frozen-dried, comminuted, sieved, homogenized, packaged, and sterilized by 60Co radiation sterilization in turn. The certified values for 18 OCPs and 16 PCBs were determined by high resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS) using isotope dilution and internal standard quantitation techniques. The certified values were validated and given based on seven accredited laboratories, and these values are traceable to the SI (international system of units) through gravimetrically prepared standards of established purity and measurement intercomparisons. The certified values of PCBs and OCPs in mussel span 4 orders of magnitude with a relative uncertainty of about 10%. This material is a natural biological material with confirmed good homogeneity and stability, and it was approved as the grade “primary reference material” (GBW10069) in June 2012 in China. This reference material provided necessary quality control products for our country to implement the Stockholm Treaty on the monitoring of persistent organic pollutants (POPs). The material is intended to be used for the method validation and quality control in the determination of OCPs and PCBs in biota samples.
    Determination of levamisole residue in animal livers by two liquid-liquid extraction steps-gas chromatography-mass spectrometry
    XU Jing*, XIAO Shanshan, DONG Weifeng, SUI Kai, CAO Jijuan*, DIAO Wenting, ZHANG Jing
    2012, 30 (09):  922-925.  DOI: 10.3724/SP.J.1123.2012.04030
    Abstract ( 1546 )   [Full Text(HTML)] () PDF (883KB) ( 441 )  
    A novel method was developed for the determination of levamisole in animal livers by liquid-liquid extraction and gas chromatography-mass spectrometry. Levamisole hydrochloride was transferred to levamisole in alkaline solution, and then extracted into ethyl acetate. Two liquid-liquid extraction steps were carried out with HCl aqueous solution and potassium hydroxide-dichloromethane system in turn, and the liposoluble substances and the water-soluble substances were removed, respectively. The qualitative and quantitative analyses of levamisole were achieved by gas chromatography-mass spectrometry (GC-MS) system. The characteristic fragments m/z 148, 176 and 204 were selected and m/z 204 was used as the quantitative ion. A good linear relationship was obtained between the peak area and the mass concentration of levamisole from 0.25 mg/L to 3.0 mg/L with the correlation coefficient of 0.999. The limit of quantitation (LOQ) for levamisole was 5 μg/kg, which was much lower than the international maximum residue limit. The average recoveries of levamisole spiked in chicken liver, duck liver, rabbit liver and pig liver samples at three spiked levels ranged from 76% to 106% with the relative standard deviations less than 9%. The method is simple and stable without tedious sample preparation, and suitable for the determination of levamisole in animal livers.
    Rapid determination of pyrethroids in tomatoes using gas chromatography combined with dispersive liquid-liquid microextraction
    LI Xianbo1,2, ZHAO Man1, LI Shengqing1, CHEN Hao1*, SHEN Jing2*
    2012, 30 (09):  926-930.  DOI: 10.3724/SP.J.1123.2012.06018
    Abstract ( 1506 )   [Full Text(HTML)] () PDF (1017KB) ( 460 )  
    An analytical method was established for the determination of three pyrethroids (bifenthrin, fenpropathrin and flucythrinate) in tomatoes using the quick, easy, cheap, effective, rugged and safe (QuEChERS) cleanup and gas chromatography. The tomato samples were extracted with acetonitrile, cleaned-up by dispersive solid-phase extraction using primary secondary amine as sorbents, concentrated by dispersive liquid-liquid microextraction (DLLME), and analyzed by gas chromatography. Factors affecting the extraction efficiency such as the type and volume of extraction solvent and the volume of dispersive and extraction time were investigated in detail. In the DLLME procedure, 40 μL chloroform was used as the extraction solvent and 1000 μL acetonitrile was used as the dispersive solvent and the extraction time was 60 s. Under the optimized conditions, the limits of detection for bifenthrin, fenpropathrin and flucythrinate were 0.5, 0.5 and 0.3 μg/kg, and the average recoveries in tomato samples at the spiked levels of 1, 10 and 50 μg/kg were 89%~109%, 92.5%~105% and 90%~108% with the relative standard deviations of 2.5%~7.6%, 2.8%~5.7% and 3.8%~9.1%, respectively. The proposed method is simple, quick, safe, reliable and applicable to analyze pyrethroid residues in tomato samples.
    Extraction chromatography of aluminium(III) and mutual separation of aluminium(III), gallium(III), indium(III) and thallium(III) with N-n-octylaniline
    Sachin R PHULE1, Haribhau R AHER1, Shashikant R KUCHEKAR1 ?, Sung-H HAN2
    2012, 30 (09):  931-937.  DOI: 10. 3724/ SP. J. 1123. 2012. 03052
    Abstract ( 1445 )   [Full Text(HTML)] () PDF (857KB) ( 395 )  
    A selective method has been developed for extraction chromatographic studies of aluminium(III) and its separation from several metal ions with a chromatographic column containing N-n-octylaniline (liquid anion exchanger) coated on silanized silica gel as a stationary phase. The aluminium(III) was quantitatively extracted with the 0.065 mol/L N-n-octylaninine from 0.013 to 0.05 mol/L sodium succinate at a flow rate of 1.0 mL/min. The extracted metal ion has been recovered by eluting with 25.0 mL of 0.05 mol/L hydrochloric acid and estimated spectrophotometrically with aurintricarboxylic acid. The effects of the acid concentration, the reagent concentration, the flow rate and the eluting agents have been investigated. The log-log plots of distribution coefficient (KdAl(III)) versus N-n-octylaniline concentration in 0.005 and 0.007 mol/L sodium succinate gave the slopes 0.5 and 0.7 respectively and showed the probable composition of the extracted species was 1:1 (metal to amine ratio) and the nature of extracted species is [RR'NH2+ Al succinate2-] org. .The extraction of aluminium(III) was carried out in the presence of various ions to ascertain the tolerance limit of individual ions. Aluminium(III) has been separated from multicomponent mixtures, pharmaceutical samples and synthetic mixtures corresponding to alloys. A scheme for mutual separation of aluminium(III), indium(III), gallium(III) and thallium(III) has been developed by using suitable masking agents. The method is fast, accurate and precise.
    Simultaneous determination of chlorpromazine and promethazine and their main metabolites by capillary electrophoresis with electrochemiluminescence
    LI Xufei, YANG Yanying, ZHOU Kaowen*
    2012, 30 (09):  938-942.  DOI: 10.3724/SP.J.1123.2012.04025
    Abstract ( 1645 )   [Full Text(HTML)] () PDF (1022KB) ( 406 )  
    Based on the phenomenon that each of chlorpromazine (CPZ), promethazine (PMZ), chlorpromazine sulfoxide (CPZSO) and promethazine sulfoxide (PMZSO) could enhance the electrochemiluminescence (ECL) intensity of tris(2,2′-bipyridyl) ruthenium, a novel and sensitive method was proposed for the simultaneous determination of CPZ, PMZ and their main metabolites using capillary electrophoresis (CE) coupled with ECL detection. The influences of several experimental parameters were explored. The optimum experimental conditions were as follows: detection potential of 1.20 V (Ag/AgCl), 40 mmol/L of phosphate buffer solution (pH 6.5) containing 5 mmol/L tris(2,2′-bipyridyl) ruthenium in ECL detection cell, running buffer solution of 18 mmol/L (pH 4.8), sample injection of 8 s at 11 kV, and separation voltage of 13.5 kV. The detection limits (3σ) of this method were 8.3×10~7g/L for CPZ, 7.2×10~6g/L for PMZ, 1.9×10~5g/L for CPZSO and 3.7×10~6g/L for PMZSO. The linear ranges of ECL intensity versus mass concentration of medicaments were 7.1×10~6~6.3×10~3g/L for CPZ, 7.5×10~5~4.6×10~3g/L for PMZ, 9.7×10~5~3.6×10~3g/L for CPZSO and 8.1×10~5~7.7×10~3g/L for PMZSO. The relative standard deviations (RSDs) of the four target compounds were not more than 3% for ECL intensity and 1% for migration time. This method has the merits of simplicity, speediness, sensitivity, small sample injection, and free from interference. This method was successfully utilized to directly and simultaneously detect CPZ, PMZ, CPZSO and PMZSO in urine samples of pet dogs.
    Simultaneous determination of chlorhexidine acetate and benzalkonium chloride in compound chemical disinfectants by capillary electrophoresis
    SONG Baohua1,2, DING Xiaojing1,3*, LI Jia1,3, WANG Zhi2*
    2012, 30 (09):  943-950.  DOI: 10.3724/SP.J.1123.2012.05022
    Abstract ( 1628 )   [Full Text(HTML)] () PDF (1002KB) ( 399 )  
    Benzalkonium chloride (BAC) is a mixture of alkyl substituted benzyl dimethylammonium chloride homologs (C12-BAC, C14-BAC and C16-BAC). Chlorhexidine acetate is a widely used effective component in compound chemical disinfectants. A method for the simultaneous determination of chlorhexidine acetate and benzalkonium chloride in compound chemical disinfectants by capillary electrophoresis (CE) was established. The CE analysis was carried out using an uncoated capillary with 50 μm i.d. and 37 cm total length. The running buffer was 150 mmol/L NaH2PO4-62.5 mmol/L H3PO4 (pH 2.5) containing 40% (v/v) acetonitrile. The sample medium was 50 mmol/L acetic acid-acetonitrile (1:1, v/v). The detection wavelength was 214 nm. The factors such as the buffer concentration and pH, the content of acetonitrile, which influenced the separation and accurate assay of compound chemical disinfectants were investigated in detail. The intra-day and inter-day precisions of the method were below 3.0% and 3.7%, respectively. The limits of detection (LOD, signal to noise ratio (S/N)=3) for chlorhexidine acetate, C12-BAC, C14-BAC and C16-BAC were 0.3, 0.5, 0.5 and 0.5 mg/L, respectively. The limits of quantification (LOQ, S/N=10) were 1.0, 1.5, 1.5, and 1.5 mg/L, respectively. The corrected peak area and the mass concentration of the four components mentioned above showed good linear relationships within the ranges of 1.0~400 mg/L, 1.5~200 mg/L, 1.5~200 mg/L and 1.5~200 mg/L, with linear correlation coefficients (r) of 0.9995, 0.9998, 0.9997 and 0.9998, respectively. The established method was used for the determination of the four disinfectants in the compound chemical disinfectants. The results were in good agreement with those obtained by the high performance liquid chromatographic method.
    Analysis of phthalate esters in plastic-packaging bags by on-line sample stacking-microemulsion electrokinetic chromatography
    XIAO Jia1, HUANG Ying1*, WANG Minyi2, CHEN Guonan3
    2012, 30 (09):  951-956.  DOI: 10.3724/SP.J.1123.2012.05024
    Abstract ( 1652 )   [Full Text(HTML)] () PDF (1096KB) ( 344 )  
    Two convenient, effective, and reproducible methods using microemulsion electrokinetic chromatography (MEEKC)-normal stacking mode (NSM) and reversed electrode polarity stacking mode (REPSM) were developed for the on-line sample stacking of phthalate esters (PAEs). REPSM coupled with MEEKC increased the sensitivity of 937.5 to 7143 times for four PAEs compared to the conventional MEEKC. The separating conditions in the MEEKC method were studied, and many factors influencing the two sample stacking processes were investigated in detail. The optimum sample matrices for the two stacking methods were as follows: 30 mmol/L sodium cholate (SC) and 30.0 mmol/L borate (pH 8.5). Additionally, sample injections as large as 3.45 kPa×40 s and 3.45 kPa×90 s were applied for NSM-MEEKC and REPSM-MEEKC, respectively. The linear relationship and reproducibility were also examined. Under the optimum conditions, the detection limits (S/N=3) of the PAEs were in the ranges of 0.021~0.33 mg/L and 0.7~4 μg/L for NSM-MEEKC and REPSM-MEEKC, respectively. The proposed REPSM-MEEKC has been successfully applied to determine PAEs in plastic-packaging bags, and the spiked recoveries were in the range of 89.1%~105.6% with satisfactory results.
    Technical Notes
    Determination of patulin in juice by ultra performance liquid chromatography-tandem mass spectrometry
    NIU Hua, FENG Lei*, NIU Zhirui, ZHU Na, ZHU Hongkun, WANG Yaqin
    2012, 30 (09):  957-961.  DOI: 10.3724/SP.J.1123.2012.04026
    Abstract ( 1593 )   [Full Text(HTML)] () PDF (879KB) ( 457 )  
    A method was developed for the simultaneous determination of patulin in juice by solid phase extraction (SPE)-ultra performance liquid chromatography coupled with electro-spray ionization tandem mass spectrometry (UPLC-ESI-MS/MS). The cloudy juice was hydrolyzed by enzyme and extracted by ethyl acetate. The extract of cloudy juice was then enriched and purified by an HLB SPE cartridge. If the juice was clear it was directly treated by the cartridge as above.The separation was performed on a C18 column with the gradient elution of acetonitrile and water. The patulin was detected by MS with electrospray negative ionization (ESI~) in the mode of multiple reaction monitoring (MRM). The good linearity was observed in the range of 1.0~500 μg/L with the correlation coefficient of 0.999 and the limit of quantitation of 5.0 μg/kg. The recoveries were in the range of 80.6%~91.8% at three spiked levels of 5.0, 25.0 and 100.0 μg/kg with the relative standard deviations of 1.5%~7.3%. It was proved to be a simple, reliable and accurate method which can fully meet the requirements of patulin detection in juice samples according to most domestic and international legislations.
    Determination of meptyldinocap residues in vegetable and fruit by liquid chromatography-tandem mass spectrometry
    Zhi-Yong ZHANG
    2012, 30 (09):  962-965.  DOI: 10.3724/SP.J.1123.2012.06008
    Abstract ( 2217 )   [Full Text(HTML)] () PDF (852KB) ( 497 )  
    A method was developed for the determination of the residues of meptyldinocap (2,4-dinitro-6-(1-methylheptyl) phenyl crotonate, 2,4-DNOPC) as 2,4-dinitrooctylphenol (2,4-dinitro-6-(1-methylheptyl) phenol, 2,4-DNOP), which is a hydrolysate of 2,4-DNOPC, in six vegetable and fruit by using liquid chromatography coupled with electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). The residues of 2,4-DNOPC in vegetable and fruit samples were extracted by the mixture of acetone, methanol and hydrochloric acid, then extracted by liquid-liquid partitioning, hydrolyzed under alkaline condition with ultrasonication, and extracted again by liquid-liquid partitioning, then analyzed by using LC-MS/MS in multiple reaction monitoring (MRM) mode via negative electrospray ionization with an Agilent ZORBAX SB-C18 column. The method was validated at four fortification levels in vegetable and fruit. The validation results were as follows: the recoveries of 2,4-DNOPC in cabbages were from 89.7% to 93.3% (the relative standard deviations (RSD) of 6.3%~8.5%), in cucumbers from 87.7% to 95.1% (RSD of 5.8%~10.4%), in tomatoes from 89.3% to 96.0% (RSD of 6.8%~9.2%), in apples from 92.0% to 98.3% (RSD of 5.1%~10.3%), in pears from 89.0% to 95.0% (RSD of 5.3%~10.2%), in grapes from 81.2% to 95.8% (RSD of 5.8%~10.4%). The limits of quantification of 2,4-DNOPC in all the test samples were 0.01 mg/kg. The results showed that the method is simple, rapid, and is characterized with acceptable sensitivity and accuracy to meet the requirements of the pesticide residue analysis. This method is applicable to confirm the residues of meptyldinocap in vegetable and fruit samples.
    Determination of the trace residues of four organochlorine pesticides in agricultural products by high performance liquid chromatography with modified multi-walled carbon nanotubes as solid phase extraction adsorbent
    PENG Xiaojun*, PANG Jinshan, DENG Aihua, LIANG Weihua, LIANG Youzhen, WEN Qijing
    2012, 30 (09):  966-970.  DOI: 10.3724/SP.J.1123.2012.05010
    Abstract ( 1627 )   [Full Text(HTML)] () PDF (2291KB) ( 453 )  
    A novel method for the simultaneous determination of the trace residues of four organochlorine pesticides such as p,p′-DDD, p,p′-DDT, o,p′-DDT and p,p′-DDE in agricultural products by multi-walled carbon nanotubes (MWNTs) modified by acid oxidation on the surface as solid phase extraction (SPE) adsorbent coupled with high performance liquid chromatography (HPLC) was developed. The effects of the surface acid oxidation, SPE operations and HPLC conditions on the determination of the four pesticide residues were investigated. Under the optimized experimental conditions, the novel method provided wide linear ranges for the pesticides with correlation coefficients of 0.9978~0.9995, the detection limit was 0.050 mg/L for each pesticides. The recoveries from the samples spiked with the pesticide standards at three concentration levels of 0.10, 2.0 and 50 mg/L were in the range of 78%~104% with the relative standard deviations (RSDs) of 2.7%~7.6%. This study indicated the MWNTs SPE was an efficient clean-up method to agricultural products (included dried orange peel, gin-seng, cabbage and tea). The proposed method showed the advantages of accuracy and sensitivity, and can meet the requirements for the determination of low residue pesticide in agricultural products. The study provides a useful method for the analysis of trace substance of agricultural products.
    Preparative isolation and purification of scopoletin from Lycium barbarum L. by high-speed counter-current chromatography
    LI Xiaoduo1, LI Xuegang2, SONG Shanghua2, ZHANG Bo2, LIU Xujing2, YE Xiaoli1*
    2012, 30 (09):  971-974.  DOI: 10.3724/SP.J.1123.2012.05037
    Abstract ( 1998 )   [Full Text(HTML)] () PDF (858KB) ( 425 )  
    An effective and rapid method for the separation of scopoletin from Lycium barbarum L. by high-speed counter-current chromatography (HSCCC) was established. The ethyl alcohol extract of the Lycium barbarum L. was initially separated using D-101 macroporous resins and further purified by HSCCC. The thin layer chromatography coupling with fluorometric spectrophotometry (TLC-F) method was used to determine the partitioning coefficient of scopoletin in different solvent systems. The results showed the solvent system of chloroform-methanol-water (10:7:3, v/v/v) was the best one for the HSCCC separation. A total of 10.2 mg of scopoletin with high purity (98.3%, analyzed by high performance liquid chromatography (HPLC)) was obtained in one step by the following separation procedures: the upper phase as the stationary phase, the lower phase as the mobile phase, with a flow rate of 1.5 mL/min, with the apparatus rotated at 850 r/min, and detected at 365 nm. The structure of the obtained compound was identified by 1H-nuclear magnetic resonance and 13C-nuclear magnetic resonance. The sample could be injected into HSCCC twice successively and the whole separation was achieved with satisfactory peak resolution. These results suggested that the TLC-F method is useful in measuring the partitioning coefficients of the target compound in HSCCC solvent systems and HSCCC is a fast and convenient method for the separation of scopoletin.