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Chinese Journal of Chromatography
2008, Vol. 26, No. 1
Online: 30 January 2008

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Analysis of hexabromocyclododecane diastereoisomers in foods of animal origin using ultra performance liquid chromatography-mass spectrometry and isotope dilution SHI Zhixiong, FENG Jinfang, LI Jingguang, ZHAO Yunfeng, WU Yongning, 2008, 26 (1):  1-5.  Abstract ( 2407 )   [Full Text(HTML)] () PDF (360KB) ( 1243 )   A method for the detection of the α, β and γ-diastereoisomers of hexabromocyclododecane (HBCDs) in foods of animal origin, such as fish, chick, milk, butter etc., was developed using ultra performance liquid chromatography-electrospray ionization mass spectrometry (UPLC-ESI-MS) and isotope dilution. The HBCDs with the spiked isotopic 13C-HBCDs, the internal standards, were extracted using Soxhlet extraction, and further purified using acidic silica treatment and solid phase extraction. The separation of HBCDs was performed on Waters ACQUITY UPLCTM system with the column of BEH C18 and the gradient elution solvent of methanol-acetonitrile and water at a flow rate of 0.2 mL/min. The HBCDs were identified on the basis of the retention times and precursor ions, and quantitatively determined under the selected ion recording mode, m/z 640.7 for the ［M-H］- ion. The limits of detection (LODs) of HBCDs ranged from 0.1 to 0.4 ng/g; and the limits of quantification (LOQs) ranged from 0.4 to 1.2 ng/g. The average recoveries ranged from 92.9% to 99.3% for the spiked levels of 0.6, 2.0 and 6.0 ng/g, with the relative standard deviations (RSDs) between 3.1% and 8.0%.

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Determination of melamine residue in plant origin protein powders using high performance liquid chromatography-diode array detection and high performance liquid chromatography-electrospray ionization tandem mass spectrometry DING Tao, XU Jinzhong, LI Jianzhong, SHEN Chongyu, WU Bin, CHEN Huilan, LI Shujuan 2008, 26 (1):  6-9.  Abstract ( 2727 )   [Full Text(HTML)] () PDF (258KB) ( 2739 )   A method for the determination of melamine residue in plant origin protein powders was developed using high performance liquid chromatography-diode array detection (HPLC-DAD) and HPLC-electrospray ionization tandem mass spectrometry (ESI-MS/MS). HPL-DAD was used in preliminary screening of the samples for melamine, and HPLC-MS/MS was used in the confirmatory of melamine. Trichloroacetic acid solution was used to precipitate proteins and to dissociate the target analyte from the sample matrix. The supernatant was cleaned up with strong cation exchange column for HPLC-MS/MS. The HPLC-DAD separation was carried out on a C18 column (250 mm×4.6 mm, 5 μm) with 0.01 mol/L sodium n-heptanesulfate （pH adjusted to 4.5 with citric acid）-acetonitrile (90:10, v/v) as mobile phase at a flow rate of 1.0 mL/min, and detected at 240 nm. HPLC-MS/MS was performed in selected ion monitoring mode with trichloroacetic acid solution as ion pair reagent. The limits of detection were 10 mg/kg and 0.5 mg/kg for HPLC-DAD and HPLC-MS/MS, respectively. The mean recoveries were 76%-88% for HPLC-DAD and 72%-82%(matrix match calibration curve) for HPLC-MS/MS and the relative standard deviations were 3.4%-6.4% for both HPLC-DAD and HPLC-MS/MS.

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Determination of endogenous steroids in urine by liquid chromatography-tandem mass spectrometry WANG Mengye, XIANG Ping, YAN Hui, SHEN Baohua, SHEN Min 2008, 26 (1):  10-14.  Abstract ( 2304 )   [Full Text(HTML)] () PDF (472KB) ( 1061 )   A method was developed for the determination of endogenous steroids in urine using liquid chromatography-tandem mass spectrometry (LC-MS/MS) with methyltestosterone as internal standard. After enzymatic hydrolysis by β-glucuronidase and liquid-liquid extraction, the urine sample was chromatographed on a Cosmosil C18 column with a mixture of methanol and ammonium acetate-formic acid (68:32, v/v) as mobile phase, then detected using MS/MS system with electrospray ionization (ESI) in multi-reaction monitoring (MRM) mode. The detection limits ranged from 0.01 ng/mL to 10 ng/mL. The recoveries ranged from 96.7% to 106.5%, and the intra- and inter-day precisions (measured as relative standard deviations) were less than 7% and 11%, respectively. With simple and fast sample preparation, the method was sensitive and specific for simultaneous determination of these 5 kinds of endogenous steroids in urine. The method has been successfully applied in pharmacokinetic study and is thus a potential alternative for gas chromatography-mass spectrometry (GC-MS) based procedures in routine analysis of endogenous steroids such as DHEA in human urine.

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Application of two-dimensional liquid chromatography coupled with mass spectrometry for the separation of active compounds in Gegen Qinlian decoction GUO Fei, WANG Yan, WANG Renfeng, YAN Chao, 2008, 26 (1):  15-21.  Abstract ( 2375 )   [Full Text(HTML)] () PDF (4302KB) ( 1238 )   An system of two-dimensional liquid chromatography (2D-LC) coupled with mass spectrometry was developed for the separation of components in Gegen Qinlian decoction, a complex traditional Chinese medicine. A CN column was used in the first dimensional chromatography, with gradient elution using water and methanol as the mobile phase A and mobile phase B, respectively; an ODS column was used in the second dimensional chromatography, with gradient elution using 20 mmol/L ammonium acetate buffer and acetonitrile as the mobile phase A and mobile phase B, respectively. The effluent was detected by mass spectrometry with electrospray ionization （ESI）/atmospheric pressure ionization （APCI） combined ion source and positive and negative scan modes. The components in Gegen Qinlian decoction was separated with the 2D-LC system with peak capacity up to 8000. Compared with UV detection, MS detected more components, especially in the negative mode. The 2D-LC/MS system provides higher peak capacity, better resolution and the capacity of peak identification. It is suitable for the analysis of complex samples such as the traditional Chinese medicine.

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Determination of 33 pesticides in tea by accelerated solvent extraction-gel permeation and solid-phase extraction purification-gas chromatography-mass spectrometry HU Beizhen, SONG Weihua, XIE Liping, SHAO Tiefeng 2008, 26 (1):  22-28.  Abstract ( 3086 )   [Full Text(HTML)] () PDF (604KB) ( 1579 )   A method has been developed for the determination of 33 pesticide residues in tea, including organophosphorous, organochlorine and pyrethroid pesticides. The target analytes were extracted with the solution of acetone/dichloromethane (1:1, v/v) using accelerated solvent extraction (ASE) and then purified using gel permeation chromatography (GPC) to eliminate most of the coextracts, such as pigments, lipids and waxes. They were further purified using Carb-NH2 and Florisil solid-phase extraction (SPE) cartridges prior to the identification using gas chromatography-mass spectrometry (GC-MS). The quantitative analysis was performed with flame photometric detector (FPD) for organophosphorous pesticides and electron capture detector (ECD) for organochlorine and pyrethroid pesticides. At the spiked level of 0.05 mg/kg, the recoveries for most pesticides were between 70%-120%; the relative standard deviations were less than 20%; the limits of detection varied from 0.005 to 0.05 mg/kg (defined in terms of 10 times of the baseline noise). This method is precise, sensitive and highly efficient in extraction. After routine applications, the results indicated that this method is suitable for the determination of pesticide residues in the tea for export.

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Determination of dioxin like polychlorinated biphenyl residues in milk using isotope dilution gas chromatography-ion trap tandem mass spectrometry DING Gangdou, LI Xiang, LIU Hanxia, ZHONG Weike, HE Yinfeng, ZHANG Yao, SUN Yizhi 2008, 26 (1):  29-34.  Abstract ( 2735 )   [Full Text(HTML)] () PDF (876KB) ( 1001 )   A method for the determination of dioxin like polychlorinated biphenyl (DL-PCB) residues in milk has been developed using high resolution gas chromatography coupled with ion trap mass spectrometry (GC-MS/MS-IT). Analytical procedure consisted of accelerate solvent extraction (ASE), lipid removal with acidic silica and clean-up using anthropogenic isolation column packed with multilayer silica. The analytes were separated on a DB-5 capillary column, detected with multiple reaction monitor mode (MRM) and quantified using internal standard calibration curve of isotope dilution technique. The correlation coefficients of calibration standard solution were above 0.9999 for all the DL-PCBs. The recoveries and relative standard deviations of labeled compound solution were in the oranges from 39% to 129% and from 5% to 22%, respectively. The detection limits in the range from 3 to 11 pg/g (fat) were established for the 12 DL-PCBs.

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Determination of furan in baby foods using headspace gas chromatography-mass spectrometry LIU Ping, XUE Ying, JIN Qingzhong, XU Jun, ZHANG Zheng, WU Guohua 2008, 26 (1):  35-38.  Abstract ( 2532 )   [Full Text(HTML)] () PDF (247KB) ( 1035 )   A method for the determination of furan in baby foods was developed using headspace gas chromatography-mass spectrometry on an HP-PLOT Q capillary column, with D4-furan as an internal standard. The linearities of detection ranged from 10 ng to 70 ng in low concentration and from 50 ng to 400 ng in high concentration, with correlation coefficients of 0.997 and 0.997, respectively. The detection limit of the method was 3.8 ng/g and the limit of quantification was 10.0 ng/g. The average recoveries at the two spiked levels in different samples ranged from 90.0% to 98.4%, and the relative standard deviations were lower than 10%.

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Multi-residue analysis of 10 β2-agonists in animal tissues using gas chromatography-mass spectrometry WU Pinggu, CHEN Huihua, WANG Qiang, YING Yongfei, ZHAO Yongxin, SONG Guoliang, XU Xiaoming 2008, 26 (1):  39-42.  Abstract ( 2768 )   [Full Text(HTML)] () PDF (271KB) ( 1145 )   A method for multi-residue analysis of β2-agonists, mabuterol, terbutaline, carbuterol, clenbuterol, cimaterol, salbutamol, clenpenterol, isoxsuprine, bambuterol and ractopamine in animal tissues using gas chromatography-mass spectrometry, based on isotope dilution and solid phase extraction has been developed. The homogenized sample was spiked with isotope-labeled internal standards, D9-clenbuterol, D3-salbutamol and D5-ractopamine, extracted with anhydrous alcohol, defatted using hexane, and cleaned-up on an SLS cartridge, and derivatized with N,O-bis(trimethylsilyl)trifluoro acetamide （BSTFA）+1%trimethylchlorosilane （TMCS）. The experimental results indicated that the recoveries were 72.8%-110.3%, and the relative standard deviations were 1.2%-11.3% in blank samples spiked with the above mentioned agonists at 2.0-10.0 μg/kg, and the corresponding detection limits were 0.5-1.0 μg/kg.

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Identification of crude oils in Bohai Sea by polycyclic aromatic hydrocarbon fingerprinting ZHAO Yuhui, SUN Peiyan, WANG Xinping, CAO Lixin, ZHOU Qing, LI Guangmei, GAO Zhenhui 2008, 26 (1):  43-49.  Abstract ( 2522 )   [Full Text(HTML)] () PDF (739KB) ( 808 )   Crude oils from different sources have quite different polycyclic aromatic hydrocarbon (PAH) distributions. Also, many PAH compounds are more resistant to weathering than their saturated counterparts (n-alkanes and isoprenoids) and volatile alkylbenzene compounds, thus PAHs become one of the most valuable classes of hydrocarbons for oil identification using fingerprinting. A reliable, effective, and accurate gas chromatography/mass spectrometry (GC/MS) method for the differentiation and source identification of crude oils by the use of PAH compounds is described. PAH components of 6 crude oil samples from 5 different platforms in 4 different oil fields in Bohai Sea were analyzed by GC/MS. Using different methods, such as the comparisons of original fingerprinting, characteristic information, and diagnostic ratios of PAHs, 6 crude oil samples were identified completely, which showed distinctive characteristics of the same platform oils. Although distinction was diminutive, it can still be identified by GC/MS. PAHs could be used in weathering check of spilled oils in identification and to ensure the correctness of the identification.

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A simple and rapid method for the determination of taxol produced by fungal endophytes from medicinal plants using high performance thin layer chromatography GANGADEVI V, MUTHUMARY J 2008, 26 (1):  50-55.  Abstract ( 2124 )   [Full Text(HTML)] () PDF (1207KB) ( 591 )   Taxol is an important anticancer drug used widely in the clinical field. In this study, some endophytic fungi were isolated from selected medicinal plants, and were screened for their potential in the production of taxol, using a rapid separation technique of high performance thin layer chromatography (HPTLC). Of the 20 screened fungi, only 13 fungal species produced taxol in the artificial culture medium. The results of HPTLC showed that the 13 fungal species had identical ultraviolet (UV) characteristics, positive reactivity with a spray reagent, yielding a blue spot, which turned to dark gray after 24 hours, and had Rf values identical to that of the authentic taxol. The amount of taxol was also quantified by comparing the peak area and the peak height of the fungal samples with those of authentic taxol.

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Determination of jervine and veratramine in veratrum plants using high performance liquid chromatography coupled with evaporative light scattering detection ZHANG Sheng, ZHOU Jianxia, SHOU Qingyao, PENG Ying, SHEN Zhengwu, 2008, 26 (1):  56-59.  Abstract ( 2225 )   [Full Text(HTML)] () PDF (381KB) ( 1032 )   A method of reversed-phase high performance liquid chromatography (HPLC) coupled with evaporative light scattering detection (ELSD) was developed for the determination of jervine and veratramine in veratrum plants. The extraction method of total active alkaloids from the raw material was also established. The separation and quantification were achieved using a Kromasil C18column (250 mm×4.6 mm, 5 μm), and a mobile phase of acetonitrile and 0.1% trifluoroacetic acid with the following gradient elution: 20%acetonitrile at the first 5 min, 20%-40%acetonitrile at the 5-30 min, 40%-20%acetonitrile at the 30-40 min, 20%acetonitrile at the 40-45 min with a flow rate of 0.8 mL/min; column temperature of 35 ℃ and monitored by an ELSD detector with the drift tube of 98 ℃ and the nitrogen flow rate of 2.2 L/min. The calibration curves for jervine and veratramine were linear over the ranges of 42.05-980 mg/L and 43.52-1020 mg/L, respectively. The recoveries were 99.2% and 101.4% with relative standard deviations of 1.7% and 2.1% (n=6), respectively. The limits of detection for jervine and veratramine in raw material were 18.37 mg/kg and 21.50 mg/kg, respectively, with 3 times of the signal to noise ratio. This HPLC-ELSD method is rapid, simple, accurate and convenient. It can be used as one of the direct and reliable means for quantitative determination of the active alkaloids in veratrum plants.

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Determination of kynurenine in serum using high performance liquid chromatography-fluorescence detection LUO Xibo, TANG Aiguo, PI Langan, XIAO Ledong, AO Xiang, PU Yanhong, WANG Rui 2008, 26 (1):  60-63.  Abstract ( 2300 )   [Full Text(HTML)] () PDF (280KB) ( 966 )   A sensitive method of high performance liquid chromatography-fluorescence detection (HPLC-FLD) for the determination of kynurenine (Kyn) in serum was developed. A 20 μL supernatant of a serum sample deproteinized by 5% perchloric acid solution was assayed and separated on a Hypersil C8 column (300 mm×6.0 mm, 10 μm) with an isocratic elution of 0.25 mol/L zinc acetate-50 mmol/L acetate containing 3% (v/v) acetonitrile. The fluorescence excitation and emission wavelengths were 365 nm and 480 nm, respectively. The limit of detection was approximately 0.04 μmol/L (signal-to-noise ratio of 3) and the linearity of the assay was from 0.098 μmol/L to 19.6 μmol/L. The relative standard deviations of intraday and interday determinations were 3.8%and 4.6%, respectively. The results indicated tryptophan (Trp), 5-hydroxytryptamine (5-HT), kynurenic acid (KYNA), phenylalanine (Phe), tyrosine (Tyr) and creatinine (Cr) had no interfering effects to the determination of Kyn. The method is of high accuracy, easy operation, satisfactory recoveries and good reproducibility, and can be used for routine analysis.

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Establishment of high performance liquid chromatographic fingerprint of Fructus schisandrae chinensis FU Shaoping, YANG Bo, CHEN Tong, YU Hongshan, JIN Fengxie 2008, 26 (1):  64-67.  Abstract ( 2420 )   [Full Text(HTML)] () PDF (3967KB) ( 1151 )   The chromatographic fingerprint was established for evaluating and controlling the quality of Fructus schisandrae chinensis by reversed-phase high performance liquid chromatography (RP-HPLC). Ten different original samples were analyzed, and the chromatographic fingerprint of Fructus schisandrae chinensis was constructed with 26 fingerprint peaks, among which 19 peaks were common fingerprint peaks and 5 main compounds were identified using the Similarity Evaluation System of Chromatographic Fingerprint of Traditional Chinese Medicine (Version 2004 A) recommended by State Food & Drug Administration. Methods of vector cosine and correlation coefficient were used to calculate the similarity of ten samples, and satisfactory results were obtained. The chromatographic fingerprint can be used to differentiate the raw materials from different sources and be served as a powerful tool for the further quality control of Fructus schisandrae chinensis.

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Investigation on the convertion between ginkgolide B and its derivative YUAN Chuanxun, PAN Jian, HU Xueqiao, XU Jing, KAI Guiqing 2008, 26 (1):  68-74.  Abstract ( 2416 )   [Full Text(HTML)] () PDF (619KB) ( 934 )   A derivative decomposed from ginkgolide B （GB）was isolated by semi-preparative chromatography. The results of the high performance liquid chromatography （HPLC）showed that the retention time of the derivative was approximately three times of that of GB with ultraviolet detection （UV）, and the derivative can not exist independently without the presence of GB. The UV spectrum showed that the λmax of the derivative was 212.1 nm and the εmax was 2.29×104, which were approximately 100 times higher than those of GB. This means a new conjugation bond has been formed and that means that the conjugation bond’s π-π* electron jump occured in the derivative. Liquid chromatography-mass spectrometry showed the molecular ion peaks of the derivative in the positive mode and negative mode were m/z 429.1 (M +Na)+ and m/z 405.2 (M-H)-, respectively. The relative molecular mass of the derivative is 406.2. The derivative showed the same mode of fragment ion as GB in the mass spectrum, which might be due to the loss of a H2O from GB. Thermal stability of GB was greater than that of the derivative. They were both easily to be dissolved in dilute alkali. When the pH gradually increases, the ring-opening speed of the derivative is higher than that of GB. The derivative was obviously affected by solvent and higher temperatures. When GB was dissolved in PEG, the peak of the derivative disappeared at 50 ℃ for 15 h or at 120 ℃ for 4 h. Besides the main peak of GB, there appeared a small peak with a retention time of 1.2-3.0 min after heating 4 h at 120 ℃. The result showed that the derivative was in a high energy state, and GB had a better stabilization. They coexisted and converted to each other. Under some specific conditions, the derivative could all convert to GB.

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Determination of ceftazidime and impurities using high performance liquid chromatography JIANG Enzhu, HU Changqin 2008, 26 (1):  75-79.  Abstract ( 2398 )   [Full Text(HTML)] () PDF (345KB) ( 1066 )   A high performance liquid chromatographic （HPLC） method for the determination of ceftazidime and impurities in ceftazidime drug was developed and verified. An Alltima C18 column (250 mm×4.6 mm, 5 μm) was used as the analysis column. Acetonitrile and phosphate buffer (22.6 g/L aqueous solution of ammonium dihydrogen phosphate, adjusted to pH 3.9 with 10%(v/v) phosphoric acid) were used as mobile phases with gradient elution at a flow rate of 1.3 mL/min. The column temperature was kept at 35 ℃, and the detection wavelength was set at 255 nm. Fourteen impurities could be well separated. The assay exhibited a good linearity in the ceftazidime concentration range of 0.267-1069 μg/mL with a correlation coefficient of 1.0000. The limits of the quantitation and qualification of ceftazidime were 3.1 ng and 0.93 ng, respectively. The relative standard deviations (RSDs) of the interday and intraday （n=3） determinations at three concentration levels were 0.72% and 0.91%, respectively. At 4 ℃ ang under darkness, ceftazidime solution was stable for 24 h. The developed method is superior to the counterparts in British and Japanese pharmacopeias in the number of the impurities separated and detected.

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Determination of cytochrome P450 3A4 activity with testosterone probe using high performance liquid chromatography ZHANG Rong, LIU Changhui, WANG Ningsheng, MI Suiqing 2008, 26 (1):  80-83.  Abstract ( 2465 )   [Full Text(HTML)] () PDF (281KB) ( 988 )   A method was established for evaluating cytochrome P450 3A4 (CYP3A4) activity using testosterone in vitro by high performance liquid chromatography-ultraviolet detection (HPLC-UV). It employed a Phenomenex C18 column (4.6 mm×150 mm, 5 μm) at 30 ℃. The mobile phase consisted of (A) methanol-acetonitrile-0.05% phosphate solution (pH 2.45) (5:15:80, v/v) and (B) acetonitrile-0.05% phosphate solution (pH 2.45) (50:50, v/v) using a linear gradient elution of 100%A-100%B at 0-18 min, then held for 5 min and returned to A. The flow rate was set at 1.0 mL/min and the ultraviolet detector was operated at 245 nm. Firstly, testosterone was incubated with rat liver microsomes in vitro and extracted by solid phase extraction (SPE). Then, the methanol eluant was obtained and evaporated to thoroughly dry with a mild stream of N2 at 37 ℃. Finally, the residues were reconstituted with 200 μL 50%(v/v) methanol and further analyzed by HPLC. The retention time of 6β-hydroxylated testosterone was 11.60 min, the linear range of the method was from 0.5 μg/mL to 32 μg/mL, and the detection limit was 0.02 μg/mL. The method recoveries were from 99.07% to 101.30% and the extraction recoveries were from 88.41% to 92.73%. The retention time of testosterone was 19.27 min, the linear range of the method was from 0.5-40 μg/mL, and the detection limit was 0.01 μg/mL. The method recoveries were from 96.50% to 98.03% and the extraction recoveries were from 89.59% to 92.66%. All of the intraday and interday relative standard deviations were less than 10%. The method is fast, accurate, sensitive and suitable for the evaluation of CYP3A4 activity and research of enzyme metabolism kinetics in vitro.

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Determination of exogenous hormones in plant tissue culture media by reversed-phase high performance liquid chromatography CHEN Yongbo, ZHAO Qinghua, JIANG Qiaolong, TENG Jianxun 2008, 26 (1):  84-87.  Abstract ( 2621 )   [Full Text(HTML)] () PDF (251KB) ( 971 )   A method of high performance liquid chromatography coupled with photodiode array detector (PAD) was established for the determination of the content ratio and type of 6 exogenous hormones in plant tissue culture media. The column was a μBondaPak C18 (3.9 mm×300 mm, 10 μm, Waters), the mobile phase was 140 mmol/L sodium acetate in triethyl amine buffer (pH 4.95)-acetonitrile (75:25, v/v), and the flow rate was 1.0 mL/min. The column temperature was 37 ℃, and the detection wavelength was 285 nm. The six hormones reached the baseline separation in 9 minutes. The linear relationship was very good in the range of 4-200 ng (r2>0.9995). The exogenous hormones in the medium were extracted by methanol after vacuum dried. The average recoveries of the exogenous hormones were more than 85%. The method can be used for the analysis of exogenous hormones of plant tissue culture media, or of unknown hormone ratio and the type of media.

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Extraction of citric acid in multi-matrixby liquid phase microextraction DING Jianhua, HE Haixia, YANG Xinlei, LUO Mingbiao, QIU Changfu, ZHAO Zhigang 2008, 26 (1):  88-92.  Abstract ( 2178 )   [Full Text(HTML)] () PDF (1790KB) ( 891 )   A method for the determination of citric acid in multi-matrix by liquid phase chromatography with liquid phase microextraction (LPME) as sample-preparation technique is introduced. The method integrates extraction, enrichment and clean-up into a single step. It is a very fast, effective and virtually “green” sample-preparation technique, which provided a good linear range (0.7-600 μg/mL) with r2=0.9995, a low detection limit (0.27 μg/mL, S/N=3) and a satisfactory relative standard deviation (RSD<5%).

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Multi-residue determination of 15 phenylurea herbicides in vegetables using solid phase extraction and online post-column ultraviolet decomposition-fluorescent derivatization-high performance liquid chromatography ZHI Jianliang, MOU Renxiang, CHEN Mingxue, ZHU Zhiwei 2008, 26 (1):  93-97.  Abstract ( 2183 )   [Full Text(HTML)] () PDF (1327KB) ( 933 )   A high performance liquid chromatographic (HPLC) method for multi-residue analysis of phenylurea herbicides in vegetables was developed. The sample was extracted with acetonitrile and cleaned up by solid phase extraction (SPE) using a Florisil cartridge. The target compounds were separated on a C18 column (250 mm×4.6 mm, 5 μm) and detected by a fluorescence detector (FLD) after online post-column ultraviolet (UV) decomposition with a UV lamp with 254 nm wavelength and fluorescent derivatization. The elution gradient, sample pretreatment and conditions of decomposition and derivatization were also studied. The elution gradient was as follows: the mobile phase started with 70%A （water） and 30%B （acetonitrile）, which was increased linearly to 50%B in 15 min, and increased 90%B in the next 15 min and held for 2 min, then returned to the initial conditions in 0.5 min. The column was equilibrated for 10 min at 25 ℃. The flow rate was 0.75 mL/min for HPLC and 0.2 mL/min for derivatization reagent. In the linear ranges of concentrations, the correlation coefficients were between 0.9986 and 1.0000. The 15 herbicides were measured in fortified onion, spinach and cucumber samples at three spiked levels, the average recoveries (n=3) were in the range of 75.3%-121.6% with relative standard deviations of 0.4%-11.6%. The limits of detection (LOD) were 0.005-0.05 mg/kg. The method is simple, sensitive, selective and qualified for phenylurea herbicide multi-residue analysis.

Reviews

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Solutions to matrix-induced response enhancement in pesticide residue analysis by gas chromatography HE Limin, LIU Xiangguo, ZENG Zhenling 2008, 26 (1):  98-104.  Abstract ( 2615 )   [Full Text(HTML)] () PDF (348KB) ( 901 )   The sample matrix can cause an enhancement in the observed chromatographic response for pesticide residues in a matrix extract compared with the same concentration in a matrix-free solution. The matrix increases the transfer of pesticides from the hot vaporizing injectors by reducing the thermal stress for labile compounds and by masking the active sites in the injector responsible for the adsorption or decomposition of polar pesticides. The use of different injector types and matrix simplification procedures can reduce matrix-induced enhancement but do not eliminate it. The most effective strategy is to use matrix-matched calibration standards or analyte protectants which equalize the response enhancement for calibration standards and sample extracts. From a practical point of view, it is important that the method used to correct for matrix-induced enhancement is compatible with low system maintenance. The different approaches for correcting matrix-induced enhancement for calibration in pesticide residue analysis are discussed and compared in this review.

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Research progress of ultrahigh-pressure liquid chromatograph and the related issues caused by ultrahigh-pressure LI Duxin, TANG Tao, WANG Fengyun, LI Tong, ZHANG Weibing, 2008, 26 (1):  105-109.  Abstract ( 1931 )   [Full Text(HTML)] () PDF (4685KB) ( 976 )   Characterized by high performance and rapid analysis, ultrahigh-pressure liquid chromatography using sub-2 μm packings becomes one of the new orientations of liquid chromatography. On the basis of the research of influence of the pressure on the properties of chromatography, the development of ultrahigh-pressure liquid chromatograph and its related issues are reviewed, and 36 papers are cited.

Technical Notes

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Determination of emamectin benzoate residue in vegetables by high performance liquid chromatography with fluorescence detection ZHANG Yan, WU Yinliang, HU Jiye, WANG Hongwei, PAN Canping, LIU Fengmao 2008, 26 (1):  110-112.  Abstract ( 3046 )   [Full Text(HTML)] () PDF (193KB) ( 1082 )   A method was developed for the determination of emamectin benzoate residue in cabbage and mushroom using solid-phase extraction (SPE) and high performance liquid chromatography (HPLC) with fluorescence detection. The sample was extracted with ethyl acetate. Further cleanup was performed on a propylsulfonic acid solid phase extraction cartridge, followed by the derivatization with trifluoroacetic anhydride in the presence of N-methylimidazole. The amount of derivatized emamectin benzoate was determined by fluorescence detector after separation by HPLC. The detection limit was 0.10 μg/kg for cabbage and mushroom samples. The recoveries of emamectin benzoate in cabbage and mushroom samples were 78.6%-84.9%. The inter-day relative standard deviation (RSD) and intra-day RSD were 2.7%-6.0% and 3.1%-8.9%, respectively, at the fortified levels of 1.0-20.0 μg/kg. The calibration curve of emamectin benzoate in vegetables at the concentration range of 0.002 mg/L to 0.10 mg/L was linear (r=0.9999).

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Determination of vitamin D in calcium fortified foods using solid-phase extraction-high performance liquid chromatography ZHAO Rong, XUE Ying, WU Guohua, ZHAO Haiyan, LUO Rencai 2008, 26 (1):  113-115.  Abstract ( 2227 )   [Full Text(HTML)] () PDF (174KB) ( 1064 )   A method for the determination of vitamin D in calcium fortified foods using solid-phase extraction-high performance liquid chromatography has been developed. The Chromabond XTR solid-phase extraction column (14500 mg, 70 mL) was used to extract and clean-up the sample. The calibration curve of vitamin D showed good linearity in the range of 0.1-100.0 μg/mL with correlation coefficient of 0.999. The limit of qualification was 0.01 μg/g and the limit of quantification was 0.03 μg/g. The average recoveries at three spiking levels were 106.2%, 99.5%, 100.1%, and the relative standard deviations were lower than 10%.