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    Chinese Journal of Chromatography
    2007, Vol. 25, No. 6
    Online: 30 November 2007

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    Articles

    Non-Equilibrium Thermodynamic Separation Theory of Nonlinear Chromatography
    Ⅱ. The 0-1 Model for Nonlinear-Mass Transfer Kinetic Processes

    LIANG Heng, JIA Zhenbin
    2007, 25 (6):  785-798. 
    Abstract ( 1854 )   [Full Text(HTML)] () PDF (3492KB) ( 685 )  

    In the optimal design and control of preparative chromatographic processes, the obstacles appear when one tries to link the Wilson’s framework of chromatographic theories based on partial differential equations (PDEs) with the Eulerian presentation to optimal control approaches based on discrete time states, such as Markov decision processes (MDP) or Model predictive control (MPC). In this paper, the 0-1 model is presented to overcome the obstacles for nonlinear transport chromatography (NTC). With the Lagrangian-Eulerian description (L-ED), one solute cell unit is split into two solute cells, one (SCm) in the mobile phase with the linear velocity of the mobile phase, and the other (SCs) in the stationary phase with zero-velocity. The thermodynamic state vector, Sk, which comprises four vector components, i.e., the sequence number, the position and the local solute concentrations in both SCms and SCses, is introduced to describe the local thermodynamic path (LTP) and the macroscopical thermodynamic path (MTP). For the NTC, the LTP is designed for a solute zone to evolve from the state, Sk, to the virtual migration state, SM, undergoing the virtual net migration sub-process, and then to the state, Sk+1, undergoing the virtual net inter phase mass transfer sub-process in a short time interval. Complete thermodynamic state iterations with the Markov characteristics are derived by using the local equilibrium isotherm and the local lumped mass transfer coefficient. When the local thermodynamic equilibrium is retained, excellent properties, such as consistency, stability, conservation, accuracy, etc., of the numerical solution of the 0-1 model are observed in the theoretical analysis and in the numerical experiments of the nonlinear ideal chromatography. It is found that the 0-1 model could properly link up with the MDP or optimal control approaches based on discrete time states.

    Determination of Glutathione in a Single Human Hepatocarcinoma Cell Using a Microfluidic Device Coupled with Electrochemical Detection

    WANG Wenlei, JIN Wenrui
    2007, 25 (6):  799-803. 
    Abstract ( 2694 )   [Full Text(HTML)] () PDF (324KB) ( 776 )  

    A method for the determination of glutathione (GSH) in a single human hepatocarcinoma cell, using a microfluidic chip coupled with electrochemical detection, was developed. In this method, the cell injection, loading, and cytolysis, as well as the transportation and detection of intracellular GSH were integrated in a microfluidic chip with a double-T injector and an end-channel amperometric detector. A single cell was loaded in the double-T injector on the microfluidic chip, using liquid pressure. The docked cell was perforated in the electrophoretic buffer containing digitonin and was lysed under a direct current electric field. The GSH from the single cell was electrokinetically transported to the separation channel and was electrochemically detected at an Au/Hg electrode. The GSH in the single cell was quantitatively determined using a calibration curve.

    Separation of Peptides Using Off-Line pH Gradient-Strong Cation Exchange Chromatography

    ZHENG Zhaobin, YING Wantao, CAI Yun, TIAN Zhongmin, QIAN Xiaohong
    2007, 25 (6):  804-808. 
    Abstract ( 2160 )   [Full Text(HTML)] () PDF (1375KB) ( 844 )  

    On the basis of theoretical pH calculation for buffer systems, an off-line linear pH gradient-strong cation exchange chromatographic method was developed for peptides separation. For the acetate buffer system, the peptides from tryptic digest of BSA were eluted by the linear pH gradient (pH 3.7-6.0) with a low concentration of ammonium acetate salt gradient, whose salt is volatile and can be easily removed by lyophilization. As for the citrate buffer system, the peptides were eluted by a wider range of linear pH gradient (pH 3.0-8.5) with a even lower concentration of ammonium citrate salt gradient. Both methods are effective for the peptides separation and before mass spectrometric detection can simplify the desalting step, which is labor-intensive and may incur significant sample loss for the routine strong cation exchange chromatography.

    Purification of Plasmid DNA Using Anion-Exchange Chromatography and Removal of Endotoxin

    PI Wenhui, SUN Congjian, SONG Zhiqiang, MA Lianying, LIU Shuping, BAI Dingping, CAI Yidong, LIU Shouren
    2007, 25 (6):  809-813. 
    Abstract ( 2950 )   [Full Text(HTML)] () PDF (592KB) ( 1335 )  

    The plasmid DNA was purified using the Fractogel EMD TMAE (M) anion exchange media. The dynamic loading capacity of this media for plasmid DNA was 0.62 mg/mL. It was found that when the lysate of bacteria was incubated with either Triton X-114 or Triton X-100 before purification, the average content of endotoxin left in the purified plasmid DNA was 6.42 EU/mg or 9.50 EU/mg, respectively. These results were much lower than that without pre-incubation (67.82 EU/mg). The purification of plasmid DNA and the removal of endotoxin were achieved in one step using anion-exchange chromatography. This method is simple, fast and of low cost.

    Analysis of 3′,5′ Reversed-Sequence Oligonucleotide Isomers by Reversed-Phase Ion-Pair Chromatography

    LUO Xuefang, CHEN Rong, FU Jingjing, HU Yuzhu
    2007, 25 (6):  814-819. 
    Abstract ( 2183 )   [Full Text(HTML)] () PDF (598KB) ( 802 )  

    3′, 5′ Reversed-sequence oligonucleotides are isomers with the same length and base composition, except with reversed base sequence. In the current work, 6 oligonucleotide model samples were designed to study chromatographic behaviour of 3′,5′ reversed-sequence isomers by optimizing effects on retention and separation. The retention factor and resolution of isomers were investigated under triethylamine-acetic acid (TEAA) concentrations of 0.025-0.15 mol/L, pH values of 5.0-6.8, temperatures of 25-45 ℃ and flow rates of 0.3-0.7 mL/min by reversed-phase ion-pair chromatography (RP-IPC). The best resolution was observed under TEAA concentration of 0.05 mol/L, pH 6.8 and flow rate of 0.4 mL/min. While the effect of temperature on the separation was not apparent, effect of initial organic strength was stronger than that of the elution gradient. The retention and separation trends of the model samples were different, and weak retention of the samples on the solid phase contributes to good separation. It is concluded that 5′end of oligonucleotide sequence showed stronger interactions with the stationary phase than the 3′end did. This research might help to understand the retention mechanism of oligonucleotides by RP-IPC.

    Preparation of Biporous Polymeric Microspheres Coupled with Mercaptopyridine and Its Application in Rapid Purification of Plasmid DNA

    LI Yuan, DOU Guosheng
    2007, 25 (6):  820-824. 
    Abstract ( 2119 )   [Full Text(HTML)] () PDF (1691KB) ( 723 )  

    Plasmid is a kind of popular nonviral vector in gene therapy. To produce large quantities of plasmid, an efficient large-scale purification process needs to be developed. In general, liquid chromatography is the most important tool for the analytical and preparative separation of plasmid DNA. In this study, biporous polymeric microspheres coupled with mercaptopyridine were synthesized for the purification of plasmid DNA. From the results of experiments, it can be inferred that the mechanism for the purification of the plasmid DNA with MP-BiPR is based on the hydrophobic interaction. When the load was 10 mL with the content of plasmid of 0.30 mg/mL and the content of RNA of 0.44 mg/mL, a flow rate was set up to 4 mL/min (20 cm/min). The separation was finished in 10 min, and the plasmid was completely recovered with undetectable impurities of nucleic acids and proteins. The load of the column for RNA was up to 2.2 mg/mL.

    Determination of Jingzhaotoxin-I Phospholipid Membrane-Binding Activities by High Performance Liquid Chromatography with Fluorescence Detection

    ZENG Xiongzhi, PI Jianhui, LIANG Songping
    2007, 25 (6):  825-829. 
    Abstract ( 2651 )   [Full Text(HTML)] () PDF (538KB) ( 670 )  

    Jingzhaotoxin-I (JZTX-I), a 33-residue polypeptide with three disulfide bonds, was a novel spider neurotoxin preferentially inhibiting cardiac sodium channel inactivation. Its activities of phospholipid membrane-binding were studied by a combination of reversed-phase high performance liquid chromatography (HPLC) and fluorescence spectroscopy. Small unilamellar vesicles binding assays showed that the partitioning of JZTX-I into lipid bilayer did not require negatively charged phospholipids. Further, JZTX-I also exhibited a blue shift of 6.4 nm or 4.7 nm as well as red-edge excitation shift of 7.4 nm or 8.0 nm in the presence of 75% 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE)/25% 1-palmitoyl-2-oleoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (sodium salt) (POPG) or 100% 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) vesicles respectively, suggesting that some tryptophan residues on the hydrophobic surface of the toxin were located within a motion restricted membrane interfacial region. Fluorescence quenching experiments suggested that some tryptophan residues of JZTX-I were positioned within the membrane and protected from aqueous quenching agents. These findings should provide further insight into the molecular mechanism of the channel gating of JZTX-I.

    Separation of Paroxetine and Its Intermediate Enantiomers by High Performance Liquid Chromatography Using Carboxy-methyl-β-Cyclodextrin as Chiral Mobile Phase Additive

    LU Tiegang, YANG Maojun
    2007, 25 (6):  830-833. 
    Abstract ( 2354 )   [Full Text(HTML)] () PDF (443KB) ( 803 )  

    A high performance liquid chromatographic method to separate the respective enantiomers of paroxetine and its intermediate was developed using chiral mobile phase additive. Separation was performed on a Diamond C18 column (4.6 mm×250 mm, 5 μm). The mobile phase was 0.1% phosphate acid-methanol (65∶35, v/v) containing 0.38 g/L carboxymethyl-β-cyclodextrin and the pH was adjusted to 7.2 by triethylamine.The detection wavelength was set at 210 nm and the temperature was 25 ℃. With this method, paroxetine’s trans/cis isomers and their enantiomers as well as intermediate HFP’s trans/cis isomers and their enantiomers were separated simultaneously. The method is simple, rapid with high resolutions.

    Determination of Dencichine in Sanchi Using Liquid Chromatography on Porous Graphitic Carbon Column

    FU Chunmei, LIU Sankang, LI Zhangwan
    2007, 25 (6):  834-837. 
    Abstract ( 2326 )   [Full Text(HTML)] () PDF (363KB) ( 763 )  

    A simple reversed-phase high performance liquid chromatographic method was developed for the determination of dencichine in sanchi on a porous graphitic carbon (PGC) column. The effects of different buffers, buffer concentrations, pH values of mobile phase and mobile phase compositions as well as column temperatures on the retention of dencichine were studied. The retention mechanism of dencichine on a porous graphitic carbon column seems to be mainly hydrophobic interaction according to the study. The chromatographic method developed was used to determine dencichine in sanchi. The calibration curve was linear in the range of about 0.22-4.4 μg (r=0.9999) and the recovery for the extract was 99.5% with the relative standard deviation of 2.2% (n=9).

    Chromatographic Behavior of Purine Derivatives on Cucurbit[6]uril Monorotaxane-Bonded Silica Stationary Phase by High Performance Liquid Chromatography

    WANG Shangwen, LI Laisheng, YI Xiuguang
    2007, 25 (6):  838-843. 
    Abstract ( 1999 )   [Full Text(HTML)] () PDF (611KB) ( 767 )  

    The chromatographic behavior of purine derivatives on a new cucurbit[6]uril monorotaxane-bonded silica stationary phase (CB6MRBS) was studied using high performance liquid chromatography both under normal and reversed-phase modes. A comparative study of this phase with ODS was carried out as well. The influences of methanol content, pH value and ionic strength of mobile phases were investigated in detail. The results showed that various interactions occurred between the analytes and CB6MRBS besides hydrophobic interaction under reversed-phase were different from those on ODS. According to the chromatographic analysis, the separation mechanism of multiple interactions also exists under normal phase. The CB6MRBS can provide various sites for analytes, such as the hydrophobic, hydrogen-bonding, π-π and dipole-dipole interactions. Separations of purine derivatives on CB6MRBS were achieved with satisfaction due to the various retention mechanisms both under reversed- and normal phase modes.

    Analysis of Three Metabolite Residues of Dipyrone in Bovine Muscle and Pork Muscle Using High Performance Liquid Chromatography

    SHEN Jincan, PANG Guofang, XIE Liqi, CHEN Peijin, HAN Ruiyang
    2007, 25 (6):  844-847. 
    Abstract ( 2372 )   [Full Text(HTML)] () PDF (312KB) ( 830 )  

    A method for the determination of metabolite residues of dipyrone, 4-formylaminoantipyrine (FAA), 4-aminoantipyrine (AA) and 4-methylaminoantipyrine (MAA) in bovine muscle and pork muscle has been developed. Homogenized muscle sample was extracted with Na2SO4-Na2SO3 solution. After filtration, the extract was cleaned-up by a C18 solid phase extraction cartridge. Prepared sample was determined using high performance liquid chromatography under the following conditions: Inertsil ODS-3 column, methanol and water as mobile phase with gradient elution, detection wavelength of 265 nm. FAA was quantified by external standard method, while AA and MAA were quantified by internal standard method using isopropylaminoantipyrine as internal standard. Limits of detection of FAA was 12.5 μg/L, while those of AA and MAA were 15.0 μg/L and 20.0 μg/L, respectively. The limit of detection of this method was 50 μg/L for all the three metabolites. The recoveries of FAA, AA and MAA were 81.3%-92.5%, 82.0%-96.0%, and 80.4%-90.6%, respectively, at the spiked levels of 50-400 μg/kg. The relative standard deviations of the method were less than 7%.

    Determination of Six Secondary Metabolites Including Chlorogenic Acid in Tobacco Using High Performance Liquid Chromatography with Coulometric Array Detection

    WANG Wenxia, LI Shuguang, ZHAO Xiaoming, LIN Bingcheng, DU Yuguang
    2007, 25 (6):  848-852. 
    Abstract ( 2222 )   [Full Text(HTML)] () PDF (331KB) ( 700 )  

    A procedure utilizing reversed-phase high performance liquid chromatography coupled with a coulometric array detection system was developed for the characterization of several major secondary metabolites in tobacco. Chromatographic separation was achieved on a Hypersil BDS C-18 column (4.6 mm×200 mm), with linear gradient elution of 5%-70%(v/v) of acetonitrile in a buffer containing 30 mmol/L NaH2PO4, 0.25 mmol/L dodecyl sulfate sodium salt (pH 3.5) at a flow rate of 1 mL/min and column temperature of 30 ℃. Ten serial coulometric detectors were set on -20, 140, 210, 310, 400, 450, 490, 730, 800 and 900 mV. The method was reliable and sensitive. The relative standard deviations ranged from 0.71% to 15.31%. The recoveries were between 52.0% and 85.2%. The detection limits were 0.2-2 ng, and there were good linear correlations when injection amount was in a range from 20 ng to 500 ng, with the regression coefficient of standard calibration curves from 0.9910 to 0.9998. This method is easy to perform and can be applied to determine secondary metabolites in tobacco.

    Determination of Six Pesticides in Milk Using Cloud Point Extraction-High Performance Liquid Chromatography

    WANG Jian, CUI Yanmei, LIU Wei, YANG Mingmin, CHEN Jianbo
    2007, 25 (6):  853-856. 
    Abstract ( 2295 )   [Full Text(HTML)] () PDF (318KB) ( 959 )  

    The feasibility of employing cloud point extraction (CPE) as extraction and preconcentration method for the recovery of herbicides from milk samples followed by high performance liquid chromatography (HPLC) analysis is demonstrated. An aqueous surfactant solution containing 60 g/L Tween 20 or Triton X-100 was heated with an appropriate concentration of (NH4)2SO4 or NaCl for the extraction of herbicides. The extract was analyzed by HPLC subsequently. Six herbicides in milk were analyzed simultaneously. The results showed that the linear dynamic ranges of detection were 20-10000 μg/L for tralkoxydim, metribuzin and bromoxynil, 30-10000 μg/L for mefenacet, and 50-10000 μg/L for bensulfuron-methyl and nicosulfuron.The correlation coefficients were 0.9981-0.9997. The average recoveries of the six herbicides ranged from 85.09% to 96.74%. The relative standard deviations for the six herbicides were in the range of 1.90%-3.98%. The limits of detection for the six pesticides were lower than the maximum residue limits (MRL) of China. The results indicate that the method is easier, faster, sensitive and produces less pollutants.

    Determination of Twelve Active Compounds in Propolis Using Ultra-Performance Liquid Chromatography

    LI Yi, ZHAO Jing, XUE Xiaofeng, ZHOU Jinhui
    2007, 25 (6):  857-860. 
    Abstract ( 2072 )   [Full Text(HTML)] () PDF (208KB) ( 852 )  

    In this study, a fast, selective and sensitive ultra-performance liquid chromatographic method (UPLC) with photodiode array detection (DAD) was developed to determine 12 active compounds, such as flavonoids, ferulic acid, caffeic acid phenethyl ester, etc. in propolis. The propolis sample was diluted with methanol and extracted by sonication. The gradient separation was achieved within 9.5 min by using an Acquity BEH C18 column (100 mm×2.1 mm, 1.7 μm) with 0.4% phosphoric acid aqueous solution and methanol as the mobile phase. The experimental parameters were optimized and adapted to analyse propolis samples from different production areas in China. The spiked recoveries were 90.1%-104.3% with relative standard deviations of 2.12%-4.90%. This method can be used as a novel method for quality control of propolis. The results are validated through testing 106 propolis samples from various production areas.

    Determination of Praziquantel Residue in Aquatic Products Using High Performance Liquid Chromatography

    SHEN Xiaosheng, YU Huijuan, CAI Youqiong, HUANG Dongmei
    2007, 25 (6):  861-863. 
    Abstract ( 1930 )   [Full Text(HTML)] () PDF (185KB) ( 751 )  

    A sensitive and simple method for the determination of praziquantel residue in aquatic products has been established. The sample was extracted with ethyl acetate for three times (20 mL, 20 mL, 10 mL) and cleaned up with an LC-Si column. The extract was separated on a ZORBAX SB-C18 column (250 mm×4.6 mm, 5 μm). Ultraviolet detection was performed at 214 nm. Acetonitrile-water (50∶50, v/v) was used as the mobile phase at a flow rate of 0.9 mL/min. The calibration curve of praziquantel in aquatic products at the concentration range of 0.02-20 mg/L was linear (r=0.99998). The recovery of praziquantel was higher than 85%. The limit of detection was 10 μg/kg (S/N>3).

    Simultaneous Determination of Canthaxanthin and Sudan Red in Salted Duck Egg Yolk by Reversed-Phase High Performance Liquid Chromatography

    WANG Quanlin, SHI Pingping, ZHANG Shufen, SHEN Jian, FU Xiao
    2007, 25 (6):  864-867. 
    Abstract ( 2873 )   [Full Text(HTML)] () PDF (185KB) ( 764 )  

    A reversed-phase high performance liquid chromatographic (RP-HPLC) method for the simultaneous determination of canthaxanthin, Sudan Red Ⅰ, Sudan Red Ⅱ, Sudan Red Ⅲ and Sudan Red Ⅳ in salted duck egg yolk has been developed. These canthaxanthin and Sudan Red dyes were extracted with a mixture of acetonitrile, methanol, and chloroform (1∶0.5∶0.5, v/v). The extract was dried by a rotary evaporator. The residue was transferred to a graduated tube and diluted to 10 mL with acetonitrile. The canthaxanthin and Sudan Red dyes were separated on a XDB-C18 column (250 mm×4.6 mm), with acetonitrile-water (95∶5, v/v) as mobile phase. They were then detected at 478 nm-520 nm-471 nm at different retention times by UV/Vis spectrophotometer. The recoveries of sudan Ⅰ, sudan Ⅱ, sudan Ⅲ, sudan Ⅳ, and canthaxanthin were 97.34%,89.56%,90.98%,93.63% and 95.15% respectively. The relative standard deviations (RSDs) were 4.7%,4.3%,5.1%,4.9% and 3.1%, respectively. The method is simple, rapid and accurate.

    Simultaneous Determination of Nine Dyestuffs and Dyes Intermediates in Cosmetics by High Performance Liquid Chromatography/Photodiode Array Detection

    CHEN Juan, WANG Chao, WANG Xing, MA Qiang, LI Nan
    2007, 25 (6):  867-870. 
    Abstract ( 2102 )   [Full Text(HTML)] () PDF (265KB) ( 859 )  

    A new analytical method based on high performance liquid chromatography/photodiode array detection (HPLC/PDA) has been established for the simultaneous determination of nine dyestuffs and dyes intermediates in cosmetics. After the cosmetics were treated by ultrasonic extraction using methanol-0.01 mol/L NH4Ac aqueous solution (2∶1, v/v), the obtained liquid samples were analyzed by HPLC using a Waters Symmetry C18 column (4.6 mm×250 mm, 5 μm). Methanol-0.01 mol/L NH4Ac aqueous solution (pH 6.2) was used as the mobile phase for gradient elution. Nine dyestuffs and dyes intermediates were completely separated within 15 min. PDA spectrum was used for assistant identification. External standard method was applied for quantitation.The average recoveries (n=8) were from 81.0% to 105.6% with relative standard deviations between 0.8% and 4.9%. The detection limits (S/N=3) were in the range of 0.1-2 μg. The method is simple, rapid, accurate and suitable for the determination of nine dyestuffs and dyes intermediates in cosmetics.

    Inverse Gas Chromatographic Study of the Oxidation Stability of Lubricating Base Oils via Solubility Parameter Calculations
    MOUSTAFA Nagy Emam, EISSA Elham Ahmed
    2007, 25 (6):  871-875. 
    Abstract ( 1873 )   [Full Text(HTML)] () PDF (292KB) ( 507 )  
    The Flory-Huggins interaction parameter (χ∞1,2) and solubility parameter (δ2) and its hydrogen bonding sensing component (δh) were determined using inverse gas chromatography (IGC). These parameters were successfully used in the probes of chemical changes that occur during the oxidation of naphthenic and paraffinic base oils in a GC column. Changes in χ∞1,2 values reflect the different types of intermolecular interactions (dispersive, polar, hydrogen bonding) of the given lubricating base oil during oxidation. The obtained results showed that δh component of solubility parameter is the most important parameter for probing the oxidative-chemical changes during the oxidation of given lubricating oils.

    Determination of Seven Nitrobenzene Compounds in Water Samples by Single-Drop Microextraction with Capillary Gas Chromatography

    MU Yingfeng, YANG Lili, HU Enyu, JI Ying
    2007, 25 (6):  876-880. 
    Abstract ( 2503 )   [Full Text(HTML)] () PDF (364KB) ( 811 )  

    A method suitable for the extraction of nitrobenzene, nitrotoluenes and nitrochlorobenzenes from water samples using single-drop microextraction with capillary gas chromatography is presented. Parameters, such as organic solvents, drop volume of organics, agitation, immerge depth of needle point, aqueous sample volume, exposure time and temperature were controlled and optimized. The developed protocol was found to yield a linear calibration curve in a concentration range from 0.8 to 32 μg/L for nitrobenzene and nitrotoluenes and a range from 0.04 to 3.2 μg/L for nitrochlorobenzenes (r2>0.999). The limits of detection were found to be in the range between 0.01 and 0.3 μg/L.The relative standard deviations (RSDs) and relative recoveries (n=5) from tap water fortified samples were 3.1%-7.9%, and 101%-105%, and from waste water fortified samples were 3.3%-7.9%, and 92.5%-97.0%, respectively. The single-drop microextraction is proved to be a environmental friendly, sensitive, fast and simple tool for the preconcentration of trace nitrobenzene, nitrotoluenes and nitrochlorobenzenes from water samples.

    Analysis of Free Terpenoids in Four Vitis vinifera Varieties Using Solvent Assisted Flavour Evaporation and Gas Chromatography-Tadem Mass Spectrometry

    JIANG Wenguang, FAN Wenlai, XU Yan, ZHAO Guang’ao, LI Jiming, YU Ying
    2007, 25 (6):  881-886. 
    Abstract ( 2401 )   [Full Text(HTML)] () PDF (504KB) ( 1100 )  

    The free terpenoids in four Vitis vinifera varieties were studied by solvent assisted flavour evaporation (SAFE) and gas chromatography-tadem mass spectrometry (GC-MS/MS). The compounds of the grapes were extracted with vibrating extraction at constant temperature, and then the non-volatiles were removed by SAFE. The volatile compounds were concentrated with a stream of nitrogen and analyzed by GC-MS/MS. The temperature of cycle water and flow rate of the sample were optimized in SAFE procedure. In the four varieties of grapes, a total of 30 terpenoids were identified by mass spectral data from NIST05a and Kovats retention indices of the standards (RIS)or from the literature (RIL), including 10 monoterpenoids, 18 sesquiterpenoids, 1 diterpenoid, and 1 triterpenoid. Twenty-eight terpenoids were detected in Cabernet Gernischt, and 16, 17, and 16 in Merlot, Cabernet Sauvignon, and Cabernet Fanc, respectively. A total of 17 sesquiterpenoids were identified in Cabernet Gernischt, and it was the richest among the four grapes. According to semi-quantitative method, the concentration of monoterpenoids in Cabernet Sauvignon was the highest among the four grapes, whereas the concentration of sesquiterpenoids in Cabernet Gernischt was the highest. The results showed that this method can be used to identify and quantify the free terpenoids in grapes.

    Application of Automatic Clean-Up System to Simultaneous Analysis of Polychlorinated Dibenzo-p-Dioxins and -Furans and Planar Polychlorobiphenyls in Milk

    ZHANG Lei, LI Jingguang, WU Yongning, ZHAO Yunfeng
    2007, 25 (6):  887-892. 
    Abstract ( 2143 )   [Full Text(HTML)] () PDF (196KB) ( 713 )  

    Since the chemical nature and toxicity of planar polychlorobiphenyls (PCBs) are similar to those of polychlorinated dibenzo-p-dioxins and -furans (PCDD/Fs). Dioxin-like PCBs and PCDD/Fs are often surveyed together in their exposure assessments. The analysis of PCBs and PCDD/Fs in breast milk is specially emphasized by World Health Organization (WHO) due to their severe toxicity. The development of a method for the simultaneous analysis of PCBs and PCDD/Fs in milk samples is invaluable. In this work, three certified milk powder materials with different PCDD/Fs levels were Soxhlet-extracted and then cleaned up using Power-Prep system automatically. PCDD/Fs and planar PCBs were determined using isotope dilution and high resolution gas chromatography-high resolution mass spectrometry. The determined values of 17 PCDD/Fs were consistent with the certified values and the relative standard deviations (RSDs) of the determined values were less than 20%. The recoveries of 13C labeled PCDD/Fs and planar PCBs, and their RSDs were within the ranges specified in EPA1613 and 1668a methods, respectively. Meanwhile, the analytical results of breast milk in an interlaboratory comparison showed that this method has good reproducibility between different laboratories. An accurate and reliable method was successfully developed and can be used in the simultaneous analysis of PCDD/Fs and planar PCBs in milk.

    Analysis of Oxygenates from Fischer-Tropsch Synthesis Oil Using Column Liquid Chromatography and Gas Chromatography-Mass Spectrography

    FAN Gaixian, XU Yuanyuan, LI Ying, LI Ying, XIANG Hongwei, LI Yongwang
    2007, 25 (6):  893-897. 
    Abstract ( 2436 )   [Full Text(HTML)] () PDF (257KB) ( 751 )  

    A liquid chromatographic column filled with silica gel of 100-200 mesh was used to separate cold trap oil from Fischer-Tropsch synthesis with dimethylsulfoxide (DMSO) as eluent. With this pretreatment method, the cold trap oil was separated into two major classes, namely, hydrocarbons and oxygenates. Minor components were also enriched and determined, and small peaks adjacent to big peaks and tailings were also well solved. The oxygenates were then analyzed with gas chromatography-mass spectrometry (GC-MS), and 139 components were identified.

    Determination of Azoxystrobin Residues in Fruits and Vegetables by Gas Chromatography/Mass Spectrometry with Solid-Phase Extraction

    BO Haibo
    2007, 25 (6):  898-901. 
    Abstract ( 2484 )   [Full Text(HTML)] () PDF (202KB) ( 859 )  

    A method was developed for the determination of azoxystrobin residues in fruits and vegetables by gas chromatography/mass spectrometry (GC/MS). Azoxystrobin residues were extracted with ethyl acetate-cyclohexane (1∶1, v/v) by ultrasonication and then they were cleaned up on a silica solid-phase extraction (SPE) column to obtain an extract suitable for analysis by GC/MS in the selective ion monitoring (SIM) mode (the selected ion: m/z 344, 372, 388 and 403). The calibration curves were linear between area and concentration of azoxystrobin from 0.01 to 1.0 mg/kg with the correlation coefficient greater than 0.99. The average recoveries from spiked fruit and vegetable matrixes at three concentrations of 0.01, 0.1, 1.0 mg/kg ranged from 85.2% to 98.2% with relative standard deviation less than 21.5%. The limit of detection was 0.01 mg/kg and the limit of quantity was 0.05 mg/kg in fruit and vegetable matrixes, respectively.

    Determination of Endosulfans and Its Metabolite in Fishery Foods Using Gas Chromatography-Mass Spectrometry with Negative Ion Chemical Ionization

    HAN Li, GUO Dehua, DENG Xiaojun, WANG Min, WANG Chuanxian, MA Yingqing
    2007, 25 (6):  902-906. 
    Abstract ( 2088 )   [Full Text(HTML)] () PDF (420KB) ( 770 )  

    Endosulfan is one of the organochlorine pesticides and contains two stereoisomers, α-endosulfan and β-endosulfan. Endosulfan sulfate is the oxide of endosulfan with toxicity comparable to endosulfan. The method was developed for the analysis of α-endosulfan, β-endosulfan and endosulfan sulfate in fishery foods. Since the maximal residue level is set at about 4-6 μg/kg in many countries, the acceptable method must be sensitive and accurate. The conditions were systematically optimized and external standard method was used for the quantification. The sample was extracted by acetone and hexane (1∶1, v/v), removed fat by transfering to acetonitrile and cold, and cleaned up with an Envi-Carb column and an LC-Alumina-N column, and analyzed by gas chromatography-mass spectrometry negative ion chemical ionization with selective ion mode. The selective ions of endosulfans and endosulfan sulfate were m/z 406, 408, 404, 372 and m/z 386, 388, 384, 422, respectively. The lowest quantitative limited level of every compound was 0.5 μg/kg, and the recoveries were 83%-105%, and the relative standard deviations were less than 13%. The method is efficient, accurate and sensitive to meet the requirements for determining endosulfans in fishery foods.

    Screening Method for Multi Herbicide and Insecticide Residues in Soybeans Using High Performance Liquid Chromatography-Time-of-Flight Mass Spectrometry

    CHU Xiaogang, YONG Wei, LING Yun, YAO Huiyuan, ZWEIGENBAUM Jerry, FANG Yanyan
    2007, 25 (6):  907-916. 
    Abstract ( 2139 )   [Full Text(HTML)] () PDF (403KB) ( 699 )  

    A new multi-residue methodology using liquid chromatography-time-of-flight mass spectrometry (LC-TOF-MS) for the quantitative analysis of pesticides has been developed. The analytical performance of the method was evaluated by screening herbicide and insecticide residues in 10 kinds of imported soybeans. The accurate mass was obtained in different spiking levels (from 0.05 to 0.10 mg/kg) and the accuracy error was lower than 3×10-6, which is well within the accepted limits for target confirmation. The linearity of response ranged from 0.03 mg/kg to 1.0 mg/kg and the correlation coefficient was greater than 0.99. The average recoveries of herbicides and insecticides ranged from 60% to 120% of the fortified herbicides and insecticides in soybeans at 0.05-0.10 mg/kg levels for the majority of herbicides and insecticides, and the relative standard deviations (RSD) were between 2.17% and 13.54%. The limits of detection (LOD) were between 0.002 and 0.026 mg/kg. The results indicated that the method developed is easier, faster, and more sensitive. It also demonstrated that this method can meet the requirements for simultaneous determination of herbicides and insecticides in soybeans. This study provides valuable evidence for that LC-TOF-MS method has the potential in screening multi pesticide residues in soybeans.

    Determination of Tetrodotoxin in Nassarius by Solid-Phase Extraction, Ultrafiltration and Liquid
    Chromatography-Mass Spectrometry

    LUO Hedong, JIA Yuzhu, ZHU Baoping
    2007, 25 (6):  917-921. 
    Abstract ( 2276 )   [Full Text(HTML)] () PDF (380KB) ( 971 )  

    A method for the determination and analysis of tetrodotoxin (TTX) in nassarius using liquid chromatography-mass spectrometry (LC-MS) has been developed.The homogenized sample was extracted with 0.03 mol/L acetic acid by heating in a boiling water-bath for 10 min and then was cleaned up on a Sep-Pak C18 cartridge column and filtered through a Mr3000 cut-off ultrafree microcentrifuge filter. Chromatographic separation was performed on an Insertsil ODS-3 column using 30 mmol/L heptafluorobutyric acid in 1 mmol/L ammonia formate buffer-methanol (99∶1, v/v) as mobile phase at a flow rate of 0.3 mL/min. TTX was identified by retention time in positive mode with selected ion monitoring (SIM).The results showed that TTX and its analogs can be separated with the method. The linear range was 0.01-10.0 mg/L and the correlation coefficients were greater than 0.995 with a detection limit of 2 μg/L (S/N=3). The average recoveries were in the range of 72.5%-80.4% and the relative standard deviations were 4.48%-8.87%. TTX of 0.04-0.50 mg/kg was found in nassarius that was collected from Fujian Province after red tide.

    Determination of Nicotinamide in Formula Milk Powder Using Liquid Chromatography-Isotope Dilution Mass Spectrometry

    HUANG Ting, ZHANG Wei, LIU Yang, LIU Jun
    2007, 25 (6):  922-925. 
    Abstract ( 2053 )   [Full Text(HTML)] () PDF (572KB) ( 948 )  

    It is important to determine trace compounds in complex matrices. Internal standards are often introduced to circumvent loss of analytes during the preparation to achieve accurate measurement. Isotope internal standards are better than other types of internal standards, due to its high similarity to analyte in chemical properties. By introducing isotope-labeled nicotinamide, as an internal standard, a method for determining nicotinamide in formula milk powder by liquid chromatography-isotope dilution mass spectrometry (LC-IDMS) was developed with a relative standard deviation of 0.94%. The results suggested that the developed LC-IDMS method has high accuracy, high specificity, high repeatability, and is suitable for the determination of vitamins in complex matrices. This method was used to perform international comparison for CCQM-P78, and the result was consistent with that of international laboratories.

    Simultaneous Identification of Fifteen Glucocorticoids in Chinese Traditional Medicine Preparations by Liquid Chromatography-Mass Spectrometry

    XIA Rui, CHE Baoquan, ZHANG Zhe
    2007, 25 (6):  926-929. 
    Abstract ( 2183 )   [Full Text(HTML)] () PDF (275KB) ( 1021 )  

    To monitoring illegal abuse of these drugs, a liquid chromatography-mass spectrometry (LC-MS) method for identification of glucocorticoids in Chinese traditional medicine preparations was developed. Samples were extracted using different methods according to the nature of products. The analyses were performed on a Diamond C18 column (5 μm, 250 mm×4.6 mm) with gradient elution using water-tetrahydrofuran (100∶1, v/v) as mobile phase A and acetonitrile-water-tetrahydrofuran (80∶20∶1, v/v) as mobile phase B. Prednisone acetate in the preparation used to cure dermatitis was identified by comparing the retention time, full scan MS, and full scan MS2.

    Determination of the Binding Constant of Bovine Serum Albumin and Gatifloxacin Using Affinity Capillary Electrophoresis

    YAO Zhi, ZHANG Haobo, WU Yi, GUO Huaizhong,
    2007, 25 (6):  930-933. 
    Abstract ( 3186 )   [Full Text(HTML)] () PDF (277KB) ( 910 )  

    The interaction between bovine serum albumin (BSA) and gatifloxacin (GT) was investigated using affinity capillary electrophoresis (ACE) method, mobility-shift method. The mobility ratio of the internal standard and the sample was used to calculate the binding constant Kb of bovine serum albumin and gatifloxacin. At first, 20 mmol/L, pH 7.4 sodium phosphate buffer solution (PBS) added with 0-1000 μmol/L GT as running buffer was used, BSA as the sample was used. Kb calculated from this experiment was 4.4×104 L/mol. Then 0-12.5 μmol/L BSA was used as an additive to do the ACE experiment, the Kb obtained was 4.2×104 L/mol. The two values matched well with each other. In order to improve the shape of the peak and restrain the adsorption of BSA to the internal wall of the quartz column, in the second method, 0.25 mol/L Gly and 0.5 mmol/L ethylenediamine tetracetate (EDTA) were added to the running buffer, and 0.5%sodium dodecyl sulfate (SDS) solution was used to rinse the column. Satisfactory effect was obtained. The Kb from fluorescence method was also calculated with a value of 2.7×104 L/mol. This work demonstrated that the determination of the binding constant by ACE is simple with high performance.

    Determination of Seven Biogenic Amines in Fish Using Micellar Electrokinetic Capillary Chromatography

    GAN Ning, LI Tianhua, WANG Luyan, JIANG Qianli
    2007, 25 (6):  934-938. 
    Abstract ( 2464 )   [Full Text(HTML)] () PDF (444KB) ( 826 )  

    A method for the determination of histamine, 2-phenylethylamine, tryptamine, putrescine, cadaverine, spermidine and spermine in fish using micellar electrokinetic capillary chromatography (MECC) was developed. Seven biogenic amines (BAs) were extracted from a sample with 6% perchloric acid, then derivatized with benzoyl chloride. 0.02 mol/L borate buffer (pH 9.2) containing 0.06 mol/L sodium deoxycholate-methanol (95∶5, v/v)was used as a running buffer. The detection wavelength was set at 214 nm. The separation was achieved within 12 min. Good linearities were observed from the calibration plots in the concentration ranges. The detection limit of histamine was 15 μg/g and those of the other amines were 5 μg/g. The developed method was successfully employed for the simultaneous determination of 7 BAs in fish sample with satisfactory results.