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Chinese Journal of Chromatography
2009, Vol. 27, No. 2
Online: 30 March 2009

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Rapid screening and confirmation of 156 pesticide residues in concentrated fruit and vegetable juices using liquid chromatography-tandem mass spectrometry LI Yan, ZHENG Feng, WANG Minglin, PANG Guofang 2009, 27 (2):  127-137.  Abstract ( 2698 )   [Full Text(HTML)] () PDF (364KB) ( 1557 )   A multiresidue analytical method was developed for the determination of 156 pesticides in concentrated fruit and vegetable juices using liquid chromatography coupled with electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). The pesticide residues were extracted from the samples by acetonitrile containing 1% acetate acid, cleaned-up by a Waters Sep-Pak Vac cartridge, eluted with 25 mL acetonitrile-toluene (3∶1, v/v) and concentrated with a rotary evaporator. The sample was redissolved in the acetonitrile-water (3∶2, v/v), then analyzed using LC-MS/MS in multiple reaction monitoring (MRM) mode via positive electrospray ionization with an Agilent ZORBAX SB-C18 column as the analytical column. The method was validated at two fortification levels in five fruit and vegetable juices, orange, apple, grape, cabbage and carrot juices. The validation results were as follows: The overall recoveries were from 57.2% to 122.7% with the relative standard deviations (RSDs) of 0.9%-19.8%, and the limits of detection (S/N=3) and the limits of quantification (S/N=10) were 0.10-56.77 μg/kg and 0.33-189.23 μg/kg, respectively. The results demonstrated that this method is simple, rapid and characterized with acceptable sensitivity and accuracy to meet the requirements of the multiple pesticide residue analysis. This method is applicable to confirm 156 pesticide residues in the above five juices.

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Simultaneous determination of 33 quinolone and sulfonamide residues in eels and shrimps by high performance liquid chromatography-tandem mass spectrometry WANG Zhijie, LENG Kailiang, SUN Weihong, NING Jinsong, ZHAI Yuxiu 2009, 27 (2):  138-143.  Abstract ( 2683 )   [Full Text(HTML)] () PDF (282KB) ( 1214 )   The method for the simultaneous determination of 33 quinolone （QN） and sulfonamide （SA） residues in eels and shrimps was developed by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The deuterium substituted reagents which were used as internal standards were added to the sample before the extraction. The sample was extracted with acidified acetonitrile, cleaned-up by hexane, and concentrated with a rotary evaporator. The mass spectrometer was operated in the positive ion mode using selected reaction monitoring for the qualitative and quantitative analysis of 33 SAs and QNs at the same time. The limits of detection for 33 SAs and QNs were 1.0 μg/kg (S/N=3), and the limits of quantification were 2.0 μg/kg (S/N=10). The correlation coefficients of linear calibration curves were over 0.99 in the concentration range of 10.0-200.0 μg/L. The average recoveries for 33 SAs and QNs were between 66% and 123%. The advantages of the method are simple operation and low cost. The method realized fast routine analysis.

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Determination of clopidol residue in poultry products by liquid chromatography-electrospray ion trap tandem mass spectrometry YANG Wenquan, XU Jinzhong, YANG Gongjun, DING Tao, QI Juanfei, LIU Han, SHEN Chongyu, WU Bin, YU Shu 2009, 27 (2):  144-148.  Abstract ( 2874 )   [Full Text(HTML)] () PDF (431KB) ( 728 )   A method is presented for the determination of clopidol residue in poultry products by liquid chromatography-electrospray ion trap tandem mass spectrometry (LC-ESI-MS/MS). Clopidol residue was extracted with methanol and cleaned-up by n-hexane from different poultry products. The extract was cleaned-up by an LC-18 column and an ion exchange solid phase extraction (SPE) column. Quantification was achieved by matrix calibration. The recoveries of clopidol in poultry products were in the range from 55.38% to 132.44% at the four spiked levels, 2, 5, 10, and 20 μg/kg. The intra-day relative standard deviation (RSD) and inter-day RSD were less than 9.54% and 15.27%, respectively. The linearity of the method was good from 1 μg/kg to 40 μg/kg. The limit of detection (LOD) was 0.5 μg/kg, and the limit of quantification (LOQ) was 2.0 μg/kg. The method is selective without interference and suitable for the determination and confirmation of clopidol residue in poultry products.

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Determination of levamisole residue in milk and milk powder by ultra performance liquid chromatography-tandem mass spectrometry BO Haibo, PANG Guofang, LUO Lili, CAO Yanzhong 2009, 27 (2):  149-152.  Abstract ( 2614 )   [Full Text(HTML)] () PDF (293KB) ( 663 )   A sensitive and selective method is presented for the determination of levamisole residues in milk and milk powder by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Levamisole in the test samples was extracted with ethyl acetate under alkaline condition, then transferred into dilute hydrochloric acid, and cleaned-up with a strong cation exchange (SCX) column to obtain an extract suitable for the analysis by UPLC-MS/MS. Levamisole was separated by a BEHC18 UPLC column and acetonitrile-1.0% formic acid (15∶85, v/v) as mobile phase, and electrospray ionization was applied and operated in the positive ion mode. The calibration curve was good linear between the peak area and the mass concentration of levamisole from 2.0 to 100.0 μg/L with the correlation coefficient of 0.997. The average recoveries of levamisole spiked in milk and milk powder samples at the three concentrations ranged from 64.5% to 102.0% with the relative standard deviations less than 13.1%. The detection limits of levamisole were 0.4 μg/kg in milk and 2 μg/kg in milk powder.

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Determination of avermectin residues in tea by ultra-performance liquid chromatography-electrospray tandem mass spectrometry YANG Fang, YANG Shoushen, LIN Yonghui, ZHENG Danping, LU Shengyu, HUANG Zhiqiang, ZHANG Ying 2009, 27 (2):  153-157.  Abstract ( 2952 )   [Full Text(HTML)] () PDF (496KB) ( 886 )   A simple and rapid analytical method for the simultaneous determination of abamectin, emamectin, eprinomectin, ivermectin, doramectin and moxidectin residues in tea by ultra-performance liquid chromatography-electrospray tandem mass spectrometry (UPLC/ESI-MS/MS) has been developed. The avermectins were extracted from the tea with acetonitrile after the tea was infiltrated in saturated aqueous NaCl solution, then cleaned up with a C18 solid phase extraction cartridge. The linear ranges were 2.0-50 μg/L and the correlation coefficients were all above 0.9920. Several UPLC-MS/MS conditions that included the mobile phase, monitor ions and the selection of calibration of the measurement were studied . The average recoveries and the relative standard deviations ranged from 61.7% to 85.4% and from 9.37% to 17.19%, respectively, in spiked samples at the concentrations of 5, 10, 20 μg/kg for moxidectin and 2, 5, 10 μg/kg for other analytes. This method is suitable for the determination of avermectin residues in tea.

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Sulfonation modification-assisted enrichment and identification of histidine-containing peptides by strong cation exchange chromatography and mass spectrometry CAO Dong, ZHOU Chunxi, ZHANG Yangjun, HAN Chunguang, DENG Yulin, 2009, 27 (2):  158-163.  Abstract ( 2547 )   [Full Text(HTML)] () PDF (692KB) ( 675 )   By the sulfonation at the N-terminal of peptides, the charge state of histidine-containing peptides is different from that of other peptides in pH<3.0 solution. Based on this difference, a new method was developed to isolate and identify sulfonated histidine-containing peptides from tryptic digest of proteins by strong cation exchange (SCX) chromatography and matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometry (MALDI-TOF MS/MS). Using the standard proteins containing histidines as the model, the methodology was evaluated. The results show that sulfonated histidine-containing peptides were efficiently enriched by SCX, and the N-terminal sulfonation of the peptides simplifies the interpretation of the acquired mass spectra and facilitates the sequencing of histidine-containing peptides by producing consecutive and predominant ions in positive mode MS2 spectra, which is thought to be the result of the charge neutralization of b ions by the N-terminal sulfonic acid group. The discrimination of b ions and y ions can greatly enhance the confidence in peptide and subsequent protein identification. It is feasible to isolate and enrich the histidine-containing peptides by using this method which has the potential applications in proteomics.

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A novel fluorescence reagent for the analysis of trace free oestradiol and oestriol in urine by reversed-phase high performance liquid chromatography with fluorescence detection and mass spectrometry identification ZHAO Huaixin, SUN Zhiwei, XIA Lian, SUN Xuejun, SUO Yourui, LI Yulin, YOU Jinmao, 2009, 27 (2):  164-168.  Abstract ( 2653 )   [Full Text(HTML)] () PDF (408KB) ( 728 )   A new fluorescent derivatization reagent, 10-ethyl-9-oxo-9,10-dihydroacridine-2-sulfonyl chloride (EASC), was synthesized. A pre-column derivatization with EASC and reversed-phase high performance liquid chromatographic (RP-HPLC) method with fluorescence （FL） detection and mass spectrometry （MS） identification was performed for the trace analysis of oestradiol (E2) and oestriol (E3) in urine. This reagent shows higher sensitivities in ultraviolet （UV）, FL and MS detection than those of dansyl chloride (DNS-Cl), and the fluorescence intensity of EASC is 1000 times higher than that of DNS-Cl. The results of derivatization indicated that the derivatives can be obtained by the labeling reaction of EASC with estradiol (E2) and estriol (E3) in the presence of NaHCO3 buffer (pH 10.5) at 60 ℃ for 3 min. The excitation wavelength (λex) and emission wavelength (λem) were 270 nm and 430 nm, respectively. The established method exhibited excellent reproducibility and recovery. The calibration curves were linear with regression coefficients over0.9990, and the detection limits (S/N=3) were 40, 31 fmol for the studied compounds. The practical applicability of the method was demonstrated by analyzing trace of free oestradiol and oestriol in the urine of root voles.

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Determination of 29 pesticide residues in tobacco by gas chromatography-electron impact ionization mass spectrometry ZOU Ximei, LIN Zhuguang, PENG Shunü, CHEN Zhaobin 2009, 27 (2):  169-175.  Abstract ( 2547 )   [Full Text(HTML)] () PDF (370KB) ( 792 )   A method was developed for rapid determination of 29 pesticide residues in tobacco based on gas chromatography coupled with electron impact ionization mass spectrometric detection (GC-EI/MS). After the optimization of different parameters, such as the extraction solvent, elution solvent, purificant, pesticides were extracted from tobacco with hexane-acetone (1∶1, v/v) in an ultrasonic bath, cleaned-up on a column, packed with Florisil and neutral alumina, eluted with dichloromethane-hexane (95∶5, v/v), and then determined by GC-EI/MS in the selected ion monitoring mode (SIM) with triphenyl phosphate (TPP) as internal standard. The recoveries were performed at 20, 50 and 100 μg/kg fortification levels for each pesticide, and the recoveries ranged from 70% to 110% with the relative standard deviations between 2% and 8%. The detection limits were less than 0.8 μg/kg for 26 pesticides except for the fenpropathrin, deltamethrin and permethrin. The method was linear over the range of 5.0-500.0 μg/kg with the correlation coefficients between 0.9994 to 0.9999. The method was successfully applied to the analysis of these pesticides in tobacco.

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Determination of 20 kinds of pesticide residues in soybeans and corn using gas chromatography-negative chemical ionization mass spectrometry coupled with offline disperse solid-phase extraction LI Chunfeng, SHEN Weijian, JIANG Yuan, SHEN Chongyu, ZHAO Zengyun, YU Keyao, GUI Qianwen, SUN Ningning, YUAN Zonghui 2009, 27 (2):  176-180.  Abstract ( 3226 )   [Full Text(HTML)] () PDF (316KB) ( 950 )   A method was developed for the determination of 20 kinds of pesticide residues in soybeans and corn with the technique of offline disperse solid-phase extraction and gas chromatography-negative chemical ionization mass spectrometry (GC-NCI/MS). The pesticides interested were extracted twice from the samples with acetonitrile. The combined extract was concentrated to dryness and redissolved in acetonitrile, then cleaned up by dispersive solid-phase extraction with sorbents of N-propyl ethylene diamine （PSA）, graphited carbon black, and C18, and determined and confirmed by GC-NCI/MS. The recoveries of all pesticides were in the range of 70%-130% at three spiked levels （5, 10 and 20 μg/kg）, and the relative standard deviations were below than 17%. The linearity of the method was good in the concentration range of 20-400 μg/L, and limits of quantification (LOQs) were no more than 2 μg/kg. The method is selective well with no interference and suitable for the confirmatory of pesticide residues in soybeans and corn.

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Determination of 28 organochlorine and pyrethroid pesticides in pine nuts using solid-phase extraction and on-line gel permeation chromatography-gas chromatography/mass spectrometry KANG Qinghe, WU Yan, GAO Kaiyang, LI Zhibin 2009, 27 (2):  181-185.  Abstract ( 2784 )   [Full Text(HTML)] () PDF (411KB) ( 1168 )   An analytical method has been developed for the determination of 28 organochlorine pesticides and pyrethroid pesticides in pine nuts. The sample was extracted With acetonitrile-water (4∶1, v/v) as the extraction solution by means of high-speed homogenization. The crude extract was purified by an Aluminium-N solid phase extraction column to remove most of the fat and sterols in the sample, then on-line gel permeation chromatography-gas chromatography/mass spectrometry （GPC-GC/MS） analysis was performed. The recoveries for the most of pesticides in the sample spiked with the standards of 0.05 mg/kg were 70%-120%, and the relative standard deviations were less than 15%. The limits of detection of 28 organochlorine pesticides and pyrethroid pesticides were 0.002-0.05 mg/kg. The linear relationship and the recovery results were satisfactory. The method is rapid, accurate, highly senstive, and can be used for the simultaneous determination of pesticide residues in pine nuts.

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Preparation of a reversed-phase capillary monolithic column and its application in the separation of polypeptide mixtures XIE Jingxin, BI Kaishun, QIAN Xiaohong, ZHANG Yangjun 2009, 27 (2):  186-190.  Abstract ( 2277 )   [Full Text(HTML)] () PDF (517KB) ( 1068 )   Capillary monolithic columns (75 μm i.d.) were prepared by the copolymerization of lauryl methacrylate as the basic monomer, ethylene dimethacrylate as the cross-linking agent and 1-dodecyl alcohol, 1,4-butanediol and dimethyl sulfoxide as the porogenic mixture. The synthetic stationary phases had better mechanical properties and chemical stabilities. A series of characterization and evaluations were performed on the capillary monolithic columns including the scanning electron microscope (SEM) images, the influences of pressure and the effects on the separation of peptide mixtures by changing the proportions of the porogen solution and cross-linking agent. The final prescription contained 15% (w/w) monomer, 15% (w/w) cross-linking agent, and 70% (w/w) porogenic agent. Then the solution was heated at 70 ℃ for 24 h. The test of relationship between column length and back pressure showed that the capillary monolithic columns prepared have superior permeability, so a longer column can be used to improve the effects of separation. The prepared capillary monolithic columns are fitted on the nano-scale high performance liquid chromatography for the separation of tryptic digests of bovine serum albumin (BSA) and human plasma samples, and better results have been obtained.

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Preparation of weak cation exchange packing based on macroporous monodisperse hydrophilic resins and their application for the separation and purification of protamine YANG Chunxia, ZHOU Jing, GONG Bolin 2009, 27 (2):  191-196.  Abstract ( 2573 )   [Full Text(HTML)] () PDF (4218KB) ( 818 )   A new kind of weak cation exchange (WCX) stationary phase for high performance liquid chromatography （HPLC） was synthesized by the chemical modification of 5.0 μm macroporous monodisperse hydrophilic poly(glycidylmethacrylate-co-ethylenedimethacrylate)(PGMA/EDMA) beads. The stationary phase was evaluated in detail to determine its separability, hydrophilicity, reproducibility and stability. It was found that the column exhibited excellent properties on the protein separation, reproducibility and stability. Four proteins were separated with linear gradient elution on the synthesized WCX stationary phase in 6 min. The highest dynamics protein loading capacity of the WCX packing for lysozyme （Lys） was 29.86 mg/g. The WCX packing was used for the fast separation and purification of protamine from carp with only one step. The purity of the obtained protamine detected by reversed-phase HPLC was 99.2%. Therefore satisfactory results have been obtained. Compared with the Shodex IEC SP-825 strong cation exchange column for the purification of protamine, the purity of protamine obtained from this column was almost same.

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Preparation of weak cation exchange monolithic column and its applications for on-line determination of nifedipine in human plasma YANG Xinru, YANG Gengliang, ZHU Tao, FENG Xiaojuan, YANG Guanqun 2009, 27 (2):  197-200.  Abstract ( 2387 )   [Full Text(HTML)] () PDF (339KB) ( 613 )   A cation exchange monolithic column was prepared with methylacrylic acid (MAA) as the functional monomer and ethylene dimethacrylate (EDMA) as the cross linker. This column was applied to remove the matrix compounds and enrich the ionic medicines in human plasma with water as the mobile phase. As a result, the human plasma samples can be directly injected into chromatographic system. The relationship between the mobile phase flow rate and back pressure was studied. The results showed that the monolithic column had good performances in lower pressure and higher permeability. In addition, the maximum adsorption of nifedipine on this monolithic column was investigated. The on-line clean-up and enrichment of samples were carried out using this column as the solid-phase extraction material and the C18 column as the analytical column. The chromatography was performed on a C18 reversed-phase high performance liquid chromatographic column with ultraviolet detection at 235 nm. The mobile phase was a mixture of methanol-water (70∶30, v/v), and the flow rate was 1.0 mL/min. The linear range of nifedipine in human plasma was 5.0-75.0 μg/L. The intra- and inter-day relative standard deviations (RSDs) were both less than 5.0%. The limit of detection (LOD) was 1 μg/L and the limit of quantification (LOQ) was 4 μg/L. In this method tedious pretreatment procedure is not necessary. It is a fast, economical, reproducible and efficient method for assaying trace nifedipine in human plasma.

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Determination of fluoxastrobin and fluacrypyrim residues in fruits and beverages by ultra performance liquid chromatography LUO Lili, BO Haibo, BI Yang, WU Yonglong 2009, 27 (2):  201-205.  Abstract ( 2572 )   [Full Text(HTML)] () PDF (256KB) ( 637 )   A method was developed for the determination of fluoxastrobin and fluacrypyrim residues in fruits and beverages by ultra performance liquid chromatography with photo-diode array (UPLC-PDA) detection. The sample was extracted with ethyl acetate-cyclohexane (1∶1, v/v) by ultrasonic, cleaned-up by gel permeation chromatography (GPC), and then determined by UPLC-PDA. The quantification was performed by external standard. A BEH C18 colunm (50 mm×2.1 mm, 1.7 μm) was used, and water-acetonitrile (3∶7, v/v) was used as mobile phase at a flow rate of 0.3 mL/min. The column temperature was set at 40 ℃, and ultraviolet absorption wavelength was set at 251 nm. The calibration curves were linear between the peak area and the concentration in the range of 0.05-2 mg/L for fluoxastrobin and fluacrypyrim, the correlation coefficients were greater than 0.999. The average recoveries spiked in fruit and beverage matrices at the three concentration levels of 0.01, 0.05, 0.1 mg/kg ranged from 82.60% to 101.11% with the relative standard deviations of 5.4%-15.3%. The limits of detection (LOD) were not greater than 6 μg/kg and the limits of quantification (LOQ) were not greater than 20 μg/kg in fruit and beverage matrices for fluoxastrobin and fluacrypyrim.

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Multi-residue determination of 11 quinolones in chicken muscle by high performance liquid chromatography with fluorescence detection LIN Baoyin 2009, 27 (2):  206-210.  Abstract ( 2661 )   [Full Text(HTML)] () PDF (318KB) ( 696 )   A high performance liquid chromatographic (HPLC) method with fluorescence detection was developed for the simultaneous determination of 11 quinolones (QNs) (norfloxacin, ofloxacin, ciprofloxacin, pefloxacin, lomefloxacin, danofloxacin, enrofloxacin, sarafloxacin, difloxacin, oxolinic acid and flumequine) residues in chicken muscle. The chicken muscle samples were extracted by 10% trichloroacetic acid/acetonitrile (7∶3, v/v) twice, diluted and cleaned up by a reversed-phase solid-phase extraction (SPE) cartridge. The QNs were separated on a reversed-phase C18 column (Hypersil BDS-C18) with mobile phase gradient elution (acetonitrile and water as mobile phases) and detected by a fluorescence detector with a wavelength program. The linear ranges of quinolone calibrations were 5-1200 μg/L in chicken muscle with the correlation coefficients more than 0.998. The recoveries for chicken muscle fortified with 11 QNs at three levels were 56%-119% with acceptable intra-batch relative standard deviations (RSD) (0.4%-16.1%) and inter-batch RSD (1.4%-23.0%). The limits of detection (LOD) and limits of quantification (LOQ) were 1-23 μg/kg and 4-40 μg/kg for the 11 QNs, respectively. The sensitivity meets the quantification requirements for the residue analysis.

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Simultaneous determination of four highly polar anti-diabetic drugs in Chinese traditional patent medicines using high performance liquid chromatography GUO Dong, Nashunchaoketu, WANG Jianghua, LIU Xiaohui, WU Shuhong, ZHAO Xiumei, YANG Binghu 2009, 27 (2):  211-215.  Abstract ( 3064 )   [Full Text(HTML)] () PDF (525KB) ( 678 )   A high performance liquid chromatographic (HPLC) method was established for the simultaneous determination of four highly polar anti-diabetic drugs, metformin hydrochloride, phenformin hydrochloride, acarbose, and voglibose, in Chinese traditional patent medicines. The separation was performed on a Thermo NH2 analytical column (4.6 mm×250 mm, 5 μm), the mobile phase consisted of 30%A and 70%B, where A included 0.06% potassium dihydrogen phosphate and 0.028% disodium hydrogen phosphate, B was acetonitrile. The flow rate was 1 mL/min, the detection wavelength was set at 195 nm, and the column temperature was 30 ℃. The limits of detection were 0.1-3 mg/L. The linear regression equation for each component was obtained, and the correlation coefficients （r2） were better than0.9981. The intra-day and inter-day relative standard deviations (RDSs) were 0.10%-5.07% and 0.19%-6.41%, respectively. The average recoveries of four anti-diabetic drugs spiked in blank Chinese traditional patent medicine matrixes were more than 80% except that for the low concentration of voglibose was 64.05%. The RSDs of the recoveries were 1.14%-4.82%. The method can be used in the analysis of the four highly polar anti-diabetic drugs in Chinese traditional patent medicines, and it is rapid, convenient, economic and specific.

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Determination of 6-hydroxy-1-methyl-1,2,3,4-tetrahydro-β- carboline, 5-hydroxytryptamine and 5-hydroxyindole acetic acid in the neonatal rat brains using high performance liquid chromatography-electrochemical detection MAO Jian, SU Yang, LUAN Yujing, CHEN Xuechai, DENG Yulin 2009, 27 (2):  216-219.  Abstract ( 2481 )   [Full Text(HTML)] () PDF (244KB) ( 625 )   A simple method was developed for the analysis of 6-hydroxy-1-methyl-1,2,3,4-tetrahydro-β-carboline (6-OH-MTHβC), 5-hydroxytryptamine (5-HT) and 5-hydroxyindole acetic acid (5-HIAA) in rat brain by high performance liquid chromatography with electrochemical detection (HPLC-ECD). The separation of the sample was performed on a Discovery HS F5 column (250 mm×4.6 mm, 5 μm) with a mobile phase of the buffer（40 mmol/L citric acid+20 mmol/L Na2HPO4+0.3 mmol/L EDTA2Na, pH 4.0）-methanol （78∶22, v/v） at a flow rate of 1.0 mL/min. The electrochemical detector was Coularray Detector-4. This method showed good linearity (r>0.9992) for the quantification of 6-OH-MTHβC, 5-HT and 5-HIAA in the concentration range of 1.0-500.0 μg/L. The limits of detection were 0.56, 0.26 and 0.53 μg/L, respectively. The recoveries of 6-OH-MTHβC, 5-HT and 5-HIAA spiked in rat brain samples were 87.1%-98.2%, 87.0%-95.3%, 90.1%-97.7%, respectively, and the relative standard deviations of intra-day and inter-day determinations were both less than 6.1%. In comparison with the control, the analysis of alcohol-exposed neonatal rat brain samples revealed a significant difference in the level of 6-OH-MTHβC (P<0.05). The method was proved to be simple, highly sensitive, and could be applied in the analysis of 6-OH-MTHβC, 5-HT and 5-HIAA in the rat brain.

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Simultaneous determination of kynurenine and kynurenic acid in serum by high performance liquid chromatography-fluorescence detection XIAO Ledong, TANG Aiguo, MO Ximing, LUO Xibo, PI Langang 2009, 27 (2):  220-223.  Abstract ( 2617 )   [Full Text(HTML)] () PDF (252KB) ( 807 )   A method of high performance liquid chromatography-fluorescence detection (HPLC-FLD) for the simultaneous determination of kynurenine (Kyn) and kynurenic acid (KYNA) in serum was developed. A 20 μL of the supernatant of a serum sample deproteinized by 5% perchloric acid solution was 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 at the beginning of the run; and 10 min later, the excitation and emission wavelengths were changed to 344 nm and 404 nm, respectively. The retention times of Kyn and KYNA were 8.1 min and 13.0 min, respectively. The linearities of the assay were from 98 to 19600 nmol/L for Kyn and from 2.62 to 1047 nmol/L for KYNA; the detection limits were 50 nmol/L for Kyn and 0.11 nmol/L for KYNA. The average recoveries were 94.88% for Kyn, and 102.72% for KYNA. The within-day and between-day relative standard deviations (RSD) were 3.87% and 3.94% for Kyn; and 3.79% and 4.71% for KYNA, respectively. The results indicated phenylalanine (Phe), tyrosine (Tyr), tryptophan (Trp), 5-hydroxytryptamine (5-HT), and creatinine (Cr) had no interfering effects to the determination of Kyn and KYNA. Kyn and KYNA concentrations in the sera of 71 health people were (1.40±0.34) μmol/L and (24.22±8.67) nmol/L, respectively. The method is simple, rapid, accurate, convenient, and suitable for routine analysis.

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Chromatographic separation of cerium(Ⅲ) in L-valine medium using poly［dibenzo-18-crown-6］ SABALE Sandip R, MOHITE Baburao S 2009, 27 (2):  224-228.  Abstract ( 1795 )   [Full Text(HTML)] () PDF (267KB) ( 366 )   A column chromatographic method has been developed for the separation and determination of cerium(Ⅲ) using poly［dibenzo-18-crown-6］. The separation was carried out in L-valine medium. The adsorption of cerium(Ⅲ) was quantitative from 1×10-1 to 1×10-4 mol/L L-valine. Amongst the various eluents, 1.0-8.0 mol/L hydrochloric acid, 1.0-8.0 mol/L hydrobromic acid, 1.0-8.0 mol/L perchloric acid, 1.0-2.0 mol/L sulfuric acid and 4.0-5.0 mol/L acetic acid, were found to be the efficient eluents for cerium(Ⅲ). The capacity of poly［dibenzo-18-crown-6］ for cerium(Ⅲ) was （0.428±0.01） mmol/g. The method was applied to the separation of cerium(Ⅲ) from associated elements link uranium(Ⅵ) and thorium(Ⅳ). It was also applied for the determination of cerium(Ⅲ) in geological samples. The method is simple, rapid and selective with good reproducibility (approximately±2%).

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Determination of active components in Radix Astragali and its medicinal preparations by capillary electrophoresis with electrochemical detection JIN Shuping, LI Ping, DONG Shuqing, WANG Qingjiang, FANG Yuzhi 2009, 27 (2):  229-232.  Abstract ( 2469 )   [Full Text(HTML)] () PDF (346KB) ( 589 )   A simple, fast, and reliable method based on capillary electrophoresis with electrochemical detection (CE-ED) was developed for the separation and determination of rutin, ferulic acid, vanillic acid, chlorogenic acid, quercetin and caffeic acid in Radix Astragali and its medicinal preparations. The effects of several important factors, such as detection potential, pH, running buffer concentration, separation voltage and injection time, were investigated to acquire the optimum conditions. Under the optimum conditions, the analytes could be separated within 17 min in a 75 cm length capillary at a separation voltage of 18 kV in a 10 mmol/L borate buffer (pH 8.2). A 300 μm diameter carbon disk electrode generated a good response at+0.95 V (vs. saturated calomel electrode (SCE)) for all analytes. The relationship between peak currents and analyte concentrations was linear over about three orders of magnitude with detection limits (S/N=3) ranging from 78 μg/L to 110 μg/L for all analytes. The average recoveries were 96.0%-103.0% with the relative standard deviations of 1.9%-3.6%(n=3). This method has been successful used for the determination of these analytes in real samples, and the assay results were satisfactory.

Technical Notes

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Determination of melamine and cyanuric acid in milk by gas chromatography-mass spectrometry LI Fengge, YAO Weiqin, SU Min, LI Shiyu, DOU Hui, SHANG Dejun, ZHU Huiping 2009, 27 (2):  233-236.  Abstract ( 2745 )   [Full Text(HTML)] () PDF (275KB) ( 1155 )   A gas chromatography-mass spectrometry method was developed for the quantitative determination and confirmation of melamine and cyanuric acid in milk. The milk sample was extracted with diethylamine-acetonitrile-water solution. The extract was evaporated to dryness and derivatized with N,O-bis(trimethylsilyl)trifluoroacetamide （BSTFA） and chlorotrimethylsilane （TMCS）, then analyzed using gas chromatography-mass spectrometry （GC-MS） in selected ion monitoring (SIM) mode. The external standards were used for the quantitative determination. The linear range was from 0.025 to 2 mg/kg. The average recoveries were 84%-87% for melamine and 75%-102% for cyanuric acid, and the relative standard deviations were 5.7%-11.7% for melamine and 4.9%-7.8% for cyanuric acid in the spiked levels at 0.5, 1.0 and 2.5 mg/kg. The limits of detection of melamine and cyanuric acid were 0.05 mg/kg and 0.10 mg/kg, respectively. The method is suitable for the quantitative determination and confirmation of melamine and cyanuric acid residues in milk.

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Simultaneous determination of nitrofurantoin and furazolidone in cosmetics using high performance liquid chromatography ZHANG Qing, WANG Chao, WANG Xing, WU Ting, MA Qiang 2009, 27 (2):  237-239.  Abstract ( 2240 )   [Full Text(HTML)] () PDF (201KB) ( 685 )   A method was developed for the simultaneous determination of nitrofurantoin and furazolidone in cosmetics using reversed-phase high performance liquid chromatography. Cosmetics samples of various types, including lotion, cream, emollient, waterpowder and lipstick, were extracted under ultrasonication with acetonitrile-methanol (1∶1, v/v). A Kromasil C18 analytical column (250 mm×4.6 mm, 5 μm) was used for the separation at 25 ℃. Acetonitrile-0.4% acetic acid (30∶70, v/v) was used as the mobile phase at a flow rate of 1.0 mL/min. The detection was performed at 365 nm by a diode array detector. The quantitative analysis was performed using external standard calibration curve. The linear ranges for nitrofurantoin and furazolidone were 0.1-20 mg/L (r=0.9999). The average recoveries were 88.0%-104.6% with the relative standard deviations of 0.5%-4.8%. The method is convenient, rapid, reliable and suitable for the determination of nitrofurantoin and furazolidone in cosmetics.

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Separation of ketoconazole enantiomers using high performance liquid chromatography with chiral mobile phase additives LIU Ai, GE Wenna, WU Shuyan, XU Qian, WANG Min, YIN Xueyan 2009, 27 (2):  240-243.  Abstract ( 2675 )   [Full Text(HTML)] () PDF (378KB) ( 732 )   A simple and effective method for the separation of ketoconazole enantiomers was developed using the chiral mobile phase additive on a C18 reversed-phase column. Several β-cyclodextrins were investigated as chiral mobile phase additives separately. The results showed that ketoconazole enantiomers were well separated by only adding sulfobutyl ether-β-cyclodextrin （SBE-β-CD） into the mobile phase. Excellent enantioseparation was achieved with the mobile phase composed of methanol-0.02 mol/L NaH2PO4 (60∶40, v/v, containing 1.0 mmol/L SBE-β-CD and 0.02% triethylamine, at pH 3.00 adjusted with phosphoric acid aqueous solution). The flow rate was 1.0 mL/min. The detection wavelength was set at 225 nm and the column temperature at 30 ℃. Under the optimized conditions, the resolution of ketoconazole enantiomers was 2.05.

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Preparative isolation and purification of flavones from Pericarpium Citri Reticulatae by high-speed counter-current chromatography SUN Yinshi, LIU Zhengbo, WANG Jianhua, WANG Ying, ZHU Lixiang, LI Lailing 2009, 27 (2):  244-247.  Abstract ( 2750 )   [Full Text(HTML)] () PDF (333KB) ( 1053 )   Three flavones were prepared, isolated and purified from Pericarpium Citri Reticulatae by high-speed counter-current chromatography (HSCCC). A two-phase solvent system composed of light petroleum-ethyl acetate-methanol-water (2∶4∶3∶3, v/v/v/v) was used. Within 6 hours, 10.1 mg of heseridin, 49.8 mg of 5,6,7,8,4′-pentamethoxyflavone and 50.6 mg of 5-hydroxy-6,7,8,3′,4′-pentamethoxyflavone with their purities over 97.0% were obtained from 4.0 g of the crude extract of Pericarpium Citri Reticulatae in one-step elution under the conditions of a flow rate of 1.70 mL/min, 800 r/min and the detection wavelength of 280 nm. The obtained fractions were analyzed by high performance liquid chromatography (HPLC), and identified by mass spectrometry (MS), 1H-nuclear magnetic resonance (NMR) and13C-NMR. The results indicate that HSCCC is a powerful technique for the purification of flavones from Citrus reticulata Blanco.