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Chinese Journal of Chromatography
2011, Vol. 29, No. 08
Online: 28 August 2011

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Highlights of researches on chromatography LIAN Hongzhen; LI Peng 2011, 29 (08):  697-698.  DOI: 10.3724/SP.J.1123.2011.00697 Abstract ( 1820 )   [Full Text(HTML)] () PDF (88KB) ( 819 )

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Porgess of new functional materials for chromatographic separation YANG Gengliang 2011, 29 (08):  699-700.  DOI: 10.3724/SP.J.1123.2011.00699 Abstract ( 1726 )   [Full Text(HTML)] () PDF (88KB) ( 858 )

Communications

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Multiple headspace solid-phase microextraction after matrix modification for the determination of ethyl carbamate in alcoholic beverages using gas chromatography ZHANG Xuena, YE Changwen, ZOU Geng, HAN Yahong, LI Xiujuan* 2011, 29 (08):  701-705.  DOI: 10.3724/SP.J.1123.2011.00701 Abstract ( 2174 )   [Full Text(HTML)] () PDF (214KB) ( 623 )   A method based on multiple headspace solid-phase microextraction (MHS-SPME) combined with gas chromatography for determining ethyl carbamate (EC) in various alcoholic beverages was established. A novel polyethylene glycol/hydroxy-terminated silicone oil fiber was used instead of commercial ones because of its high extraction ability. Anhydrous sodium sulphate was added to modify the matrix and the extraction efficiency of EC was greatly improved. The optimum conditions for MHS-SPME were as follows: extraction time, 10 min; extraction temperature, 35 ℃; Na2SO4 addition, 4.0 mg Na2SO4 per microliter of sample; volume of sample, 20 μL. The proposed method was linear in the range of 0.04 to 100 mg/L with a correlation coefficient of 0.9997. The limit of detection was 34 μg/L and the repeatability of six replicates was 2.19%. The method was used to determine EC in various alcoholic beverages. The concentrations obtained were compared with those obtained by standard addition method and no statistically significant differences were observed. The application of MHS-SPME avoids the matrix effect, which commonly appears in SPME-based analysis. The results indicate that MHS-SPME has a great potential for EC quantification of complex samples due to its simplicity, sensitivity, reliability, ease of operation and environmental protection, especially for the analysis of a large number of samples in different matrices.

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Proteomic peptide library for determination of substrate motif of casein kinase 2 2011, 29 (08):  706-711.  DOI: 10.3724/SP.J.1123.2011.00706 Abstract ( 2089 )   [Full Text(HTML)] () PDF (360KB) ( 561 )   Substrate motif is of great importance in kinase-substrate recognition and contributes a lot to the understanding of signal transduction. In this study, a proteomic peptide library was generated to determine substrate motif of casein kinase 2. Firstly, whole cell lysate was digested by trypsin to generate a large number of candidate peptides, which were then incubated with alkaline phosphotase to dephosphorylate intrinsic phosphopeptides. Then, the unphosphorylated peptide mixture was incubated with casein kinase 2 (CK2) and adenosine-triphosphate (ATP) for 30 min, and the resulting phosphopeptides were enriched by immobilized metal affinity chromatography (IMAC) followed by reversed-phase liquid chromatographic separation coupled with tandem mass spectrometry detection. Finally, the 472 unique phosphopeptides and 451 unique phosphorylation sites were identified, resulting in the determination of a motif of S/T-D/E-x-D/E for CK2. This method enables accurate determination of substrate motif in a short time and can be readily applied to other kinases.

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Determination of 12 steroid hormone residues in pig tissues by liquid chromatography-tandem mass spectrometry combining with library search CAI Qinren1*, FENG Jiawang1, ZHANG Yi1, PENG Yufen1, XUE Liangchen1, DU Zhifeng2 2011, 29 (08):  712-717.  DOI: 10.3724/SP.J.1123.2011.00712 Abstract ( 2063 )   [Full Text(HTML)] () PDF (236KB) ( 605 )   A method was developed for the simultaneous determination and identification of 12 steroid hormone residues in pig tissues, including stanolone, aldosterone, boldenone, danazol, metandienone, methyltestosterone, nadrolone, norethindrone, progesterone, stanozolol, testosterone and testosterone propionate, using liquid chromatography-tandem triple-quadrupole linear ion trap mass spectrometry(LC-MS/MS). Homogenized pig tissue samples were purified with a Waters MCX solid phase extraction column after enzymatic hydrolysis by β-glucuronidase, then separated on a Venusil MP C18 column (100 mm×2.1 mm, 3 μm) using gradient elution with the mobile phases of acetonitrile and water with 0.1% (v/v) formic acid. A multiple reaction monitoring (MRM) as survey scan and an enhanced product ion (EPI) scan as dependent scan were performed in an information dependent acquisition (IDA) experiment. The compound identification was carried out by library search with a newly developed MS/MS library based on EPI spectra at three different collision energies in positive mode. The results showed that the limits of detection (LODs, S/N=3) were in the range of 0.2~0.5 μg/kg for the steroid hormones, and with a good linearity (r＞0.99) ranged from 0.5 to 100.0 μg/L. The average recoveries (n=6) of the 12 steroid hormones spiked in pig tissue samples at 5.0 μg/kg ranged from 72.0% to 98.1% with the relative standard deviations (RSDs) between 3.1% and 12.5%. The method was applied for the qualitative and quantitative determination of steroid hormone residues in pig tissues with sensitive and accurate characteristics.

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Simultaneous determination of 15 anti-obesity drugs in blood by high performance liquid chromatography-tandem mass spectrometry CHE Baoquan1,2, HUANG Xiaojun2, ZHANG Zhe2, WANG Zhibin2, DENG Yulin1* 2011, 29 (08):  718-722.  DOI: 10.3724/SP.J.1123.2011.00718 Abstract ( 1956 )   [Full Text(HTML)] () PDF (183KB) ( 589 )   An analytical method for the simultaneous determination of 15 anti-obesity drugs (caffeine, sibutramine, phenformin, etc.) in blood sample was developed using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). After a simple protein precipitation step, the HPLC separation was performed on an UltimateXB-C18 column with methanol and 20 mmol/L ammonium acetate (containing 0.1%(v/v) of glacial acetic acid) as the mobile phases in a gradient elution mode. The MS/MS detection was achieved by electrospray ionization in both positive and negative modes by rapid switching with selective reaction monitoring (SRM). The results showed that the limits of quantification of all anti-obesity drugs were in the range of 0.001~0.05 mg/L. The calibration curves of all anti-obesity drugs showed good linearity and the correlation coefficients were more than 0.99. The recoveries of all anti-obesity drugs at 3 spiked levels were in the range of 77.3%~110.8% with the intra-day and inter-day precisions less than 12.3%. The mass spectrum characterizations of 15 anti-obesity drugs were studied. The method is sensitive and reproducible for the detection of the 15 anti-obesity drugs in blood, and can also be applied to the determination of the anti-obesity drugs in pharmaceuticals or foods.

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Simultaneous determination of 17 preservatives and antioxidants in condiments using ultra performance liquid chromatography-electrospray ionization tandem mass spectrometry 2011, 29 (08):  723-730.  DOI: 10.3724/SP.J.1123.2011.00723 Abstract ( 2299 )   [Full Text(HTML)] () PDF (260KB) ( 644 )   An ultra performance liquid chromatography-electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS) method was developed for the simultaneous determination of 11 preservatives and 6 antioxidants in condiments. The condiment sample with low fat or middle fat was diluted with saturated NaCl solution (adjusting pH to 2~3 with phosphoric acid), then extracted with acetonitrile. The extract was purified using liquid-liquid extraction with hexane, and the sample with middle fat was further purified using solid phase extraction with a C8 column. The condiment sample with high fat was diluted with hexane, then dissolved with saturated NaCl solution (adjusting pH to 2~3 with phosphoric acid), and extracted with acetonitrile. The extract was purified using solid phase extraction with a C8 column. The analysis was performed on a C18 column (150 mm×2.1 mm, 1.7 μm) using a gradient elution with the mobile phases of 20 mmol/L ammonium acetate buffer and acetonitrile, and determined by tandem mass spectrometry in negtive ESI mode under multiple reaction monitoring (MRM) mode. The method had good linearity (r≥0.9955). The limits of quantification (LOQs) (S/N=10) of 17 analytes ranged from 0.05 mg/kg to 5 mg/kg. The recoveries ranged from 79.7% to 118% at three spiked levels, the relative standard deviations (RSDs) ranged from 0.57% to 13.1%. The method can be applied for the determination of preservatives and antioxidants in condiments.

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Simultaneous determination of six organophosphorous flame retardants in textiles by gas chromatography-tandem mass spectrometry combined with microwave assisted extraction WANG Chengyun*, LI Lixia, XIE Tangtang, ZHANG Weiya, LIU Caiming, ZHU Naiqing 2011, 29 (08):  731-736.  DOI: 10.3724/SP.J.1123.2011.00731 Abstract ( 2086 )   [Full Text(HTML)] () PDF (205KB) ( 641 )   An ultra performance liquid chromatography-electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS) method was developed for the simultaneous determination of 11 preservatives and 6 antioxidants in condiments. The condiment sample with low fat or middle fat was diluted with saturated NaCl solution (adjusting pH to 2~3 with phosphoric acid), then extracted with acetonitrile. The extract was purified using liquid-liquid extraction with hexane, and the sample with middle fat was further purified using solid phase extraction with a C8 column. The condiment sample with high fat was diluted with hexane, then dissolved with saturated NaCl solution (adjusting pH to 2~3 with phosphoric acid), and extracted with acetonitrile. The extract was purified using solid phase extraction with a C8 column. The analysis was performed on a C18 column (150 mm×2.1 mm, 1.7 μm) using a gradient elution with the mobile phases of 20 mmol/L ammonium acetate buffer and acetonitrile, and determined by tandem mass spectrometry in negtive ESI mode under multiple reaction monitoring (MRM) mode. The method had good linearity (r≥0.9955). The limits of quantification (LOQs) (S/N=10) of 17 analytes ranged from 0.05 mg/kg to 5 mg/kg. The recoveries ranged from 79.7% to 118% at three spiked levels, the relative standard deviations (RSDs) ranged from 0.57% to 13.1%. The method can be applied for the determination of preservatives and antioxidants in condiments.

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Simultaneous determination of six organophosphorous flame retardants in textiles by gas chromatography-tandem mass spectrometry combined with microwave assisted extraction FU Shanliang, DING Li, ZHU Shaohua, JIAO Yanna, GONG Qiang, CHEN Jitao, WU Xinhua, WANG Libing* 2011, 29 (08):  737-742.  DOI: 10.3724/SP.J.1123.2011.00737 Abstract ( 2251 )   [Full Text(HTML)] () PDF (267KB) ( 616 )   An effective method was established for the simultaneous determination of six banned organophosphorous flame retardants in textiles by gas chromatography-tandem mass spectrometry (GC-MS/MS) combined with microwave assisted extraction (MAE). By investigating the extraction efficiency of 12 different extraction solvents for the target analytes, the optimal conditions were that the sample was extracted by microwave assisted extraction using acetone as the solvent at 76 ℃ for 30 min. Then the extract was analyzed by GC-MS/MS in multiple reaction monitoring (MRM) mode, and the concentration of each analyte was calibrated by external standard method. The linear ranges of tris-(1-aziridinyl)phosphine oxide (TEPA), tris-(2-chloroethyl)phosphate (TCEP), tris-(1,3-dichloropropyl)phosphate (TDCP), bis-(2,3-dibromopropyl)phosphate (DDBPP), tri-o-cresyl phosphate (TOCP) and tris-(2,3-dibromopropyl)phosphate (TRIS) were 9.17~366.80, 0.95~75.98, 1.04~83.20, 41.60~832.00, 3.80~75.90, and 40.48~809.60 μg/L, respectively, the correlation coefficients were not less than 0.9975, while the limits of quantification (LOQ) (S/N=10) were 3.0, 0.2, 0.3, 25.0, 2.5 and 29.0 μg/kg, respectively. The spiked recoveries varied from 82.62% to 96.88% with the relative standard deviations of 3.80% to 8.79%. The proposed method was successfully applied to the determination of organophosphorous flame retardants in eight commercial textiles. The experimental results demonstrated that the method developed is simple, rapid, sensitive and accurate, which could satisfy the demand of the analysis of banned organophosphorous flame retardants in textiles.

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Determination of polybrominated diphenyl ethers in human serum using solid-phase extraction and gas chromatography coupled with negative chemical ionization mass spectrometry HUANG Feifei, ZHAO Yunfeng, LI Jingguang*, WU Yongning 2011, 29 (08):  743-749.  DOI: 10.3724/SP.J.1123.2011.00743 Abstract ( 1946 )   [Full Text(HTML)] () PDF (276KB) ( 553 )   A simplified analytical method comprised of solid-phase extraction (SPE) and gas chromatography coupled with negative chemical ionization mass spectrometry (GC-NCI/MS) has been developed for the determination of 10 polybrominated diphenyl ethers (PBDEs) congeners in human serum. After the extraction by OasisHLB custom-made SPE cartridges, the lipids in serum were decomposed by concentrated sulfuric acid directly added on the SPE column. The solvent for protein cleanup and the SPE conditions, such as elution solvent and its volume were optimized. The recoveries of the PBDEs spiked in fetal bovine serum relative to internal standards were in the range of 78.5%~109.7% at five spiked levels (three spiked levels for BDE-209). The intra-day relative standard deviations (RSDs) were between 0.3% and 7.4%, while the inter-day RSDs were between 1.42% and 14.1%. The limits of detection (LOD, S/N=3) and the limits of quantification (LOQ, S/N=10) were in the range of 0.10~0.27 ng/L and 0.35~0.91 ng/L respectively for all PBDEs, except BDE-209. The LOQ (blank concentration value×3) for BDE-209 was 7.91 ng/L. The method was verified by accurate analysis of organic contaminant standard reference materials (SRM) 1957 and 1958. The results indicated that the proposed method is sensitive, accurate, fast, simple, low solvent consumption and suitable for the determination of tri- to deca-BDE in human serum.

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Determination of imidocarb residue in swine tissues by high performance liquid chromatography 2011, 29 (08):  750-754.  DOI: 10.3724/SP.J.1123.2011.00750 Abstract ( 1921 )   [Full Text(HTML)] () PDF (191KB) ( 444 )   A quantitive method for the determination of imidocarb residue in edible tissues of swine by high performance liquid chromatography (HPLC) was developed. The analyte was digested by β-glucosidase first, and then extracted with 1 mol/L hydrochloric acid. The aqueous phase was back-extracted with the mixture of hexane-isoamyl alcohol (3:2, v/v) for the purification. The mobile phases were acetonitrile (phase A) and 0.0075 mol/L 1-pentansulfonic acid sodium aqueous solution containing 0.1% triethylamine, adjusted to pH 3.0 with glacial acetic acid (phase B). The analyte was detected by ultraviolet absorption spectroscopy after the separation was achieved on a C18 RP column. The linear range was 10~10000 μg/L, and the correlation coefficient was more than 0.999. The limit of detection (LOD) was 10 μg/kg, and the limit of qualification (LOQ) was 20 μg/kg. The mean recoveries of imidocarb in swine tissues at the added levels of LOQ, MRL (maximum residue limit) and 2MRL ranged from 80.04% to 110.32%, and the relative standard deviations (RSDs) of intra- and inter-day analyses ranged from 0.82% to 10.00%. The method is simple and sensitive for the quantification of imidocarb residue in swine tissues.

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Simultaneous determination of 9 heterocyclic aromatic amines in poultry products by solid-phase extraction-high performance liquid chromatography SHAO Bin1, PENG Zengqi1*, YANG Hongsheng2, WU Guanghong2, YAO Yao1, WAN Kehui1 2011, 29 (08):  755-761.  DOI: 10.3724/SP.J.1123.2011.00755 Abstract ( 2022 )   [Full Text(HTML)] () PDF (246KB) ( 581 )   A method was developed for the simultaneous determination of 9 heterocyclic aromatic amines (HAAs) including 2-amino-3-methylimidazo［4,5-f］quinoline (IQ), 2-amino-3,4-dimethylimidazo［4,5-f］quinoline (MeIQ), 2-amino-3,8-dimethylimidazo［4,5-f］quinoxaline (MeIQx), 2-amino-3,4,8-trimethyl-imidazo［4,5-f］quinoxaline (4,8-DiMeIQx), 2-amino-1-methyl-6-phenylimidazo［4,5-b］pyridine (PhIP), 3-amino-1-methyl-5H-pyrido［4,3-b］indole (Trp-p-2), 3-amino-1,4-dimethyl-5H-pyrido［4,3-b］indole (Trp-p-1), 9H-pyrido［3,4-b］indole (Norharman), 1-methyl-9H-pyrido［3,4-b］indole (Harman)) in poultry products using solid-phase extraction-high performance liquid chromatography (SPE-HPLC). The performance of 3 different organic extraction solutions, 2 solid phase extraction (SPE) procedures, three different reversed-phase columns and five different mobile phases were tested for optimizing separation conditions of the 9 HAAs from poultry products. In the end, ethyl acetate was selected as the extraction solution, and the extract was purified with propylsulfonic acid silica (PRS) and C18 SPE columns. The analysis was performed on a TSK-gel ODS-80TM column using a gradient elution with the mobile phases of 0.05 mol/L aqueous acetic acid-ammonium acetate buffer (pH 3.4) and acetonitrile. The results showed that the average recoveries (n=6) of the 9 HAAs spiked in meat samples at 3 levels ranged from 60.47% to 90.55% with the relative standard deviations (RSDs) between 0.49% and 9.74%, and the limits of detection (LODs, S/N=3) were in the range of 0.1~3.6 μg/kg. The method is simple, rapid, accurate and sensitive enough for the analysis of HAAs in poultry products.

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Determination of 12 sunscreen agents in cosmetics by high performance liquid chromatography HE Qiaosang1*, XU Na2, LI Jing1, LIAO Shangfu1 2011, 29 (08):  762-767.  DOI: 10.3724/SP.J.1123.2011.00762 Abstract ( 2191 )   [Full Text(HTML)] () PDF (218KB) ( 603 )   A comprehensive analytical method based on high performance liquid chromatography (HPLC) has been developed for the determination of 12 sunscreen agents in cosmetics. The cosmetic samples were extracted by methanol. The target compounds were separated on an SB-C8 column (250 mm×4.6 mm, 5 μm) in gradient elution mode using methanol and 0.1%(v/v) formic acid aqueous solution as mobile phases. The detective wavelength was 311 nm. The linear plots were obtained between 1.0 and 500 mg/L with good correlation coefficients larger than 0.9995. The limits of detection (LODs) for this method were in the range of 0.002~0.1 mg/L. The spiked recoveries of commercial cosmetics were in the range of 97.4%~107.5% with the relative standard deviations of 1.54%~4.98%. The results indicated that the developed method is simple, rapid, accurate and suitable for the determination of 12 sunscreen agents in cosmetics samples.

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Determination of propofol in human plasma by microemulsion liquid chromatography ZHANG Ting1, CUI Ying2* 2011, 29 (08):  768-772.  DOI: 10.3724/SP.J.1123.2011.00768 Abstract ( 2032 )   [Full Text(HTML)] () PDF (169KB) ( 431 )   A microemulsion liquid chromatographic (MELC) method was developed for the determination of propofol in human plasma. The assay was performed on a Hypersil BDS C18 column, and the effects of each component in the microemulsion mobile phase on the elution were investigated. The optimized microemulsion mobile phase consisted of 0.5% acetic acid containing 3.0% sodium dodecylsulfate, 0.8% n-heptane, 6.0% n-butanol. The flow rate was 1.0 mL/min, and the separation was operated at ambient temperature. The fluorescence excitation and emission wavelengths were 274 nm and 312 nm, respectively. The plasma samples were diluted with the mobile phase and centrifuged before injection. The calibration curve of propofol was linear within the range of 0.25~10 μg/mL. The method recoveries were (98.2±1.9)%－(104.6±2.2)%. The intra-day relative standard deviations (RSDs) of peak area were 1.42%~2.43%, and the inter-day RSDs were 2.75%~4.79%. The method is simple and reproducible. It can be used for the determination of propofol in human plasma.

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Determination of 23 organochlorine pesticides in soil and sediment by gas chromatography coupled with dual columns and dual electron capture detectorsorganochlorine pesticides in soils and sediments by Microwave Extraction and GC coupled with dual-column and dual-ECD ZHU Hengyi1, LIU Wenyuan1,2*, DING Xining3, ZHAO Yonggang3 2011, 29 (08):  773-780.  DOI: 10.3724/SP.J.1123.2011.00773 Abstract ( 2505 )   [Full Text(HTML)] () PDF (317KB) ( 440 )   Gas chromatography (GC) coupled with dual columns and dual electron capture detectors (ECD) was established to determine 23 organochlorine pesticides in 5 soil and 5 sediment samples. Microwave assisted extraction and solid phase extraction with a Florisil column and sulfur cleanup with copper powder were used in sample pre-processing. Chromatographic analysis was performed on DB-XLB and DB-1701 capillary columns by internal standard method. This method showed good extraction efficiency, high sensitivity and good reproducibility. In the same linear range of 0.005~0.5 mg/L of 23 pesticides, the correlation coefficients were higher than 0.997. The average spiked recoveries were 50%~119% with the relative standard deviations (RSDs) of 0.9%~16.1% (n=6) in 5 soil samples, and were 52%~120% with RSDs of 0.3%~28.4% (n=6) in 5 sediment samples, respectively. The detection limits were 0.00005~0.0005 mg/kg. The results indicate that this method is suitable for the determination of the 23 organochlorine pesticides in soil and sediment samples.

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Design and implementation of thermal conductivity detector for gas chromatography MAO Xiufen, JIN Bin*, SU Lei 2011, 29 (08):  781-785.  DOI: 10.3724/SP.J.1123.2011.00781 Abstract ( 2146 )   [Full Text(HTML)] () PDF (315KB) ( 624 )   In order to improve the performance of thermal conductivity detector (TCD) for gas chromatography, a precision constant current source circuit and a difference voltage detection circuit were designed. The constant current source was designed with a field effect tube IRF460, operational amplifiers AD8672 and a linear optical coupler HCNR201. The difference voltage detecting circuit was designed with two pieces of AD8597. The noise model of the difference voltage detecting circuit was established and the theoretical value of minimum noise was calculated. The experimental results showed that the baseline noise of TCD came up to 4 μV, that the baseline drift of TCD came up to 15 μV in 50 min, that the fluctuation of constant current source was about 1 μA, which were superior to current technical specification of existing TCD. The introduced design scheme and noise analysis method have reference value for new TCD design.

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Preparation and evaluation of open tubular capillaryelectrochromatographic column modified with carboxymethyl chitosan ZHOU Sunying1,2, LIN Xucong1, XIE Zenghong1* 2011, 29 (08):  786-790.  DOI: 10.3724/SP.J.1123.2011.00786 Abstract ( 1819 )   [Full Text(HTML)] () PDF (227KB) ( 425 )   Via covalent coupling of epoxy group, an open tubular column covalently modified with carboxymethyl chitosan (CMC) as stationary phase was prepared. The parameters of column pretreatment, silanization and chemically bonding of CMC were optimized. The morphology of inner wall of the open tubular column was observed by scanning electron microscope (SEM), which showed that the inner wall of the prepared column was evenly coated with a polymer film. Either positive or negative electroosmotic flow (EOF) could be achieved by varying the pH values of running buffer. Good reproducibility was obtained with the relative standard deviations (RSDs) of EOF less than 0.8% for run-to-run (n=6), less than 3.5% for day-to-day (n=3), less than 4.3% for column-to-column (n=3) and less than 6.1% for batch-to-batch (n=3). Nucleotides (AMP, GMP, CMP and UMP) were analyzed on the open tubular column modified with CMC, with high column efficiencies ranging from 36000 to 182000 plates/m. The results indicate that the developed method is effective, easy and stable.

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Analysis of nine narcotics in urine by microemulsion electrokinetic chromatography-field amplified sample injection ZHANG Yu1, LI Qin2, LU Minghua3, ZHANG Lan2, CHEN Guonan2, CAI Zongwei2,3* 2011, 29 (08):  791-797.  DOI: 10.3724/SP.J.1123.2011.00791 Abstract ( 2498 )   [Full Text(HTML)] () PDF (276KB) ( 442 )   A simple, sensitive and reproducible method using microemulsion electrokinetic chromatography (MEEKC)-field amplified sample injection (FASI) was developed for the analysis of nine narcotics (morphine, codeine, naloxone, heroin, thebaine, cocaine, pethidine, fentanyl and methadone) in urine. In the MEEKC method, sodium dodecyl sulfate (SDS), 1-butanol and ethyl acetate were used as surfactant, co-surfactant and organic solvent, respectively. The effects of the acidity and concentration of borate buffer, SDS, 1-butanol and ethyl acetate contents were investigated. The optimum concentrations (by mass fraction) of microemulsion system were 0.6% SDS, 1.2% 1-butanol, 0.6% ethyl acetate and 97.6% 10 mmol/L Na2B4O7 buffer (pH 9.5). The applied voltage was 25 kV. FASI was coupled with the MEEKC method to increase the sensitivity. Under the optimum conditions, the nine narcotics were baseline separated within 15 min and the detection limits (S/N=3) were in the range of 0.3~8.0 μg/L. The spiked recoveries in urine samples were between 79.4% and 119.9% with the intraday relative standard deviations (RSDs) less than 5.5%. The developed method has been successfully applied to the analysis of methadone in the samples from in vitro metabolism study.

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Analysis of glucocorticoids in hair by pressurized capillary electrochromatography with ultra-violet detection LI Boxiang, ZHENG Minmin, LU Lanxiang, WU Xiaoping* 2011, 29 (08):  798-804.  DOI: 10.3724/SP.J.1123.2011.00798 Abstract ( 1883 )   [Full Text(HTML)] () PDF (305KB) ( 537 )   This study describes an effective and convenient method for the separation and determination of the glucocorticoids residues in hair. Compared to most reported methods of high performance liquid chromatography using gradient elution，this analysis is performed utilizing isocratic elution reversd-phase pressurized capillary electrochromatography with UV detection. Eight glucocorticoids (betamethasone, dexamethasone, prednisone, prednisolone, prednisolone acetate, hydrocortisone acetate, cortisone acetate and corticosterone) are separated within 20min on a reversed-phase C18 column, with the Tris buffer (pH 8, 1.5 mM)– acetonitrile (65:35, v/v) as mobile phase and 245nm as the UV detection wavelength, and the flow rate of pump is 0.05 mL/min. All the compounds show good linearity in the concentration range of analysis. Detection limits (LODs) for all glucocorticoids are of 10-6 mol/L levels. The proposed method is applied to the analysis of hair samples. The interference of hair matrices were effectively eliminated by enzymatic digestion followed by a methanol extraction and a solid phase extraction (SPE) clean up step. Average recoveries of 71–85% at different fortified levels of glucocorticoids are achieved. This non-invasive method is useful for rapidly estimating the level of drug exposure in drug abuse and monitoring the compliance of therapeutic drugs.