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Chinese Journal of Chromatography
2012, Vol. 30, No. 05
Online: 28 May 2012

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Progress in techniques for determination of microcystins in aquatic products FAN Sai, ZHAO Rong-*, LI Bing, LIU Wei, WU Guo-Hua 2012, 30 (05):  434-439.  DOI: 10.3724/SP.J.1123.2011.09031 Abstract ( 1870 )   [Full Text(HTML)] () PDF (178KB) ( 578 )   Microcystins (MCs) produced by blue-green algae, is one of the algal toxins with features of highest frequency and production. MCs could cause serious multi-organ toxicity, genetic toxicity and carcinogenicity. Monitoring of MCs residue in aquatic products is important for evaluating the potential risk for human beings. Therefore, the trace analytical technique of MCs is needed. In this paper, the progress of the microcystins extraction, purification and analytical techniques is reviewed.

Articles

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Preparation of poly(methyl acrylate) microfluidic chips with surface-modified by hyperbranched polyamide ester and their application in the separation of biomolecules LIU Bing1, LIN Dong2, XU Lin1, LEI Yanhui1, BO Qianglong1, SHOU Chongqi1* 2012, 30 (05):  440-444.  DOI: 10.3724/SP.J.1123.2011.12041 Abstract ( 1774 )   [Full Text(HTML)] () PDF (245KB) ( 290 )   The surface of poly(methyl acrylate) (PMMA) microfluidic chips were modified using hyperbranched polyamide ester via chemical bonding. The contact angles of the modified chips were measured. The surface morphology was observed by scanning electron microscope (SEM) and stereo microscope. The results showed that the surface of the modified chips was coated by a dense, uniform, continuous, hydrophilic layer of hyperbranched polyamide ester. The hydrophilic of the chip surface was markedly improved. The contact angle of the chips modified decreased from 89.9° to 29.5°. The electro osmotic flow (EOF) in the modified microchannel was lower than that in the unmodified microchannel. Adenosine and L-lysine were detected and separated via the modified PMMA microfluidic chips. Compared with unmodified chips, the modified chips successfully separated the two biomolecules. The detection peaks were clear and sharp. The separation efficiencies of adenosine and L-lysine were 8.44×104 plates/m and 9.82×104 plates/m respectively, and the resolutions (Rs) was 5.31. The column efficiencies and resolutions of the modified chips were much higher than those of the unmodified chips. It was also observed that the modified chips possessed good reproducibility of migration time. This research may provide a new and effective method to improve the hydrophilicity of the PMMA surface and the application of PMMA microfluidic chips in the determination of trace biomolecules.

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Simultaneous determination of penicillin G and its major metabolites in blood using ultra performance liquid chromatography-tandem mass spectrometry CHEN Cong1,2,3, YAN Hui1, SHEN Baohua1, ZHUO Xianyi1* 2012, 30 (05):  445-451.  DOI: 10.3724/SP.J.1123.2011.11036 Abstract ( 1644 )   [Full Text(HTML)] () PDF (285KB) ( 313 )   A fast method for the quantitative determination of penicillin G (PEN G), penicilloic acid and penilloic acid in blood with ultra performance liquid chromatography-electrospray tandem mass spectrometry was developed. A simple deproteinization of the blood was used with a mixed solution of acetonitrile and water (4:1, v/v) as extraction solvent. The blood extract was directly injected onto an LC column. The chromatographic separation of the components was performed on a BEH C18 column (50 mm×2.1 mm, 1.7 μm) using acetonitrile and water containing 0.1% formic acid. The mass spectrometer was operated in positive electrospray ion mode. Finally, the analysis was carried out with multiple reaction monitoring (MRM) mode. The limits of detection (LODs) for these three compounds were in the range of 0.1 to 2.0 ng/mL and the limits of quantification (LOQs) in the range of 0.5 to 5.0 ng/mL. Within the linear range, the correlation coefficients (r) of PEN G and its metabolites were all more than 0.9974. Accuracies for these targeted compounds were ranged from 92.3% to 105.5%, and the within-day precisions were less than 10%. The stabilities of the components were evaluated in the temperature range from 18 to ~80 ℃, and the mass concentration of penicillin G was decreased significantly with the extensions of storage temperature and storage time. Biological samples of the rats medicated with PEN G were analyzed using the developed method. The results show that PEN G can just be detected at 0.5 h after administration. However, the detection time limitation of penicilloic acid can be extended to 36 h. The established method has been further expanded for the applicability of forensic identification, and has a reference value for the detection of penicillin G residue in food.

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Determination of ilaprazole in beagle plasma and its pharmacokinetics by high performance liquid chromatography-mass spectrometry ZHOU Lijun1,2, LI Jinglai2, WANG Xiaoying2, QIAO Jianzhong2, ZHANG Zhenqing2* 2012, 30 (05):  452-456.  DOI: 10.3724/SP.J.1123.2011.12081 Abstract ( 2134 )   [Full Text(HTML)] () PDF (187KB) ( 384 )   A sensitive, simple and specific high performance liquid chromatography-electrospray ionization mass spectrometry method was developed for the determination of ilaprazole in the plasma of beagles administered via i.v. bolus doses of ilaprazole. The procedure employed buspirone as the internal standard and a simple protein precipitation step. The separation was achieved using a C18 column (100 mm×2.1 mm, 5 μm) with a mobile phase consisting of water-methanol-acetonitrile (69:8:23, v/v/v) containing 0.1% (v/v) formic acid at a flow rate of 0.2 mL/min. The detection was accomplished by a mass spectrometer using selected ion monitoring (SIM) in positive mode. The linearity was from 5 μg/L to 10000 μg/L with a sensitivity of 5 μg/L as the lower limit of quantification. The inter- and intra- day precisions were within 9.00%. The mean recoveries at three spiked levels were about 106% and the matrix effects were less than 142.0%. The method described above was successfully applied to analyze the beagle plasma samples of ilaprazole in a pharmacokinetic study. The area under the plasma concentration-time curve (AUC(0~∞))of ilaprazole after i.v. doses of 0.2, 0.8 and 3.2 mg/kg were (2.4×104±3×103)、(8.8×104±1.6×104) and (5.4×105±8×104) μg/L•min, respectively. On the basis of AUC, the pharmacokinetic property of ilaprazole was proposed to be linear dynamics.

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Simultaneous determination of 10 unapproved sedative drugs in feeds by ultra-performance liquid chromatography-quadrupole-time-of-flight mass spectrometry XU Cheng-Bao-1, 2 , SUO Ran-1*, ZHANG Feng-2*, CHU Xiao-Gang-2, DING Fei-2, 3 , LING Yun-2, YANG Min-Li-2, SUN Li-2 2012, 30 (05):  457-462.  DOI: 10.3724/SP.J.1123.2011.12032 Abstract ( 1736 )   [Full Text(HTML)] () PDF (242KB) ( 368 )   A new analytical method using ultra-performance liquid chromatography-quadrupole-time-of-flight mass spectrometry (UPLC-Q-TOF-MS) was developed for screening and confirmation of 10 unapproved sedative drugs in feeds. The samples were extracted using the solution of methanol-0.1 mol/L HCl (9:1, v/v), and the extracts were centrifuged and then directly purified through MCX cartridges. The identification and detection were achieved in positive electrospray ionization (ESI) mode using Q-TOF-MS. The potential of UPLC-Q-TOF MS for confirmatory analysis was shown by determining the accurate mass of all the compounds and fragment ions upon collision-induced-dissociation (CID) at different energies. The extra mass measurement errors for all the sedative drugs were found to be within 5 ppm. The calibration graphs were linear in the concentration range of 5~100 μg/L with the correlation coefficients more than 0.99 for the 10 drugs. The limits of quantification (LOQ, S/N=10) were 8 μg/kg for nitrazepam, zolpidem and thioridazine; 10 μg/kg for thriazolam, estazolam, diazepam, promethazine, chlorpromazine and midazolam; 20 μg/kg for clozapine. The recoveries for all the compounds in feeds were 60.6%~108.5% with the relative standard deviations less than 10% at the spiked levels of LOQ, 2LOQ and 4LOQ.

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Determination of virginiamycin M1 and S1 residues in livestock and poultry products by liquid chromatography-tandem mass spectrometry QIU Yuanjin*, YANG Fang, LIU Zhengcai, LIN Yonghui, LIU Suzhen 2012, 30 (05):  463-467.  DOI: 10.3724/SP.J.1123.2012.01020 Abstract ( 1750 )   [Full Text(HTML)] () PDF (185KB) ( 302 )   A liquid chromatography-tandem mass spectrometry method was established for the determination of virginiamycin M1 and S1 residues in livestock and poultry products. The sample was extracted by methanol-acetonitrile solution (1:1, v/v). The supernatant was diluted with 0.01 mol/L ammonium dihydrogen phosphate solution, then purified and concentrated on an Oasis HLB cartridge. The separation of virginiamycin M1 and S1 was performed on a Luna C18 column with the mobile phases acetonitrile and 5 mmol/L ammonium acetate aqueous solution (containing 0.1% (v/v) formic acid) in a gradient elution mode. The identification and quantification of the drugs were carried out by positive electrospray ionization (ESI+) in the multiple reaction monitoring (MRM) mode using external standard method. The calibration curves showed good linearity in the range of 0.15~10.0 μg/L with correlation coefficients (r2) above 0.999. The limits of quantities (LOQs) were both 0.25 μg/kg. The average recoveries of the two drugs spiked at 0.25, 0.5 and 2.5 μg/kg levels in different matrices were between 71.2% and 98.4%, and the relative standard deviations (RSDs) were between 3.6% and 15.4%. The method is simple, rapid, sensitive and accurate. It is suitable for the confirmation and quantification of virginiamycin M1 and S1 residues in livestock and poultry products.

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Simultaneous determination of 8 polybrominated biphenyls in human serum using gas chromatography-mass spectrometry LIU Xiao1,2, LI Jingguang1,2*, HUANG Feifei2,3, WU Yongning2 2012, 30 (05):  468-473.  DOI: 10.3724/SP.J.1123.2011.11055 Abstract ( 1886 )   [Full Text(HTML)] () PDF (198KB) ( 311 )   A comprehensive analytical method based on gas chromatography-mass spectrometry (GC-MS) has been developed for the simultaneous determination of 8 polybrominated biphenyl congeners (PBBs: BB-15, 18, 52, 101, 153, 180, 194 and 206) in human serum. After the protein was removed, the sample was cleaned-up by an Oasis HLB solid-phase extraction (SPE) cartridge, then purified further by a two-layer cartridge containing activated silica gel and a mixture of silica gel and sulfuric acid, in which elution solvent was optimized. The eluent was evaporated to about 100 μL by a gentle nitrogen stream for GC-MS analysis. The separation was performed on a DB-5ms column (15 m×0.25 mm×0.1 μm) and the qualitative and quantitative analyses were carried out in electron impact (EI) selected ion monitoring (SIM) mode, in which isotope was used as internal standard. The limits of detection (LODs, 3.14 times of standard deviation) and the limits of quantification (LOQs, 10 times of standard deviation) were 0.002~0.029 ng/mL and 0.008~0.092 ng/mL respectively for the 8 PBBs. The average recoveries for all PBBs at three spiked levels were 74.24%~119.49% with the relative standard deviations in the range of 1.23%~12.02%. The method was verified by accurate analysis of BB-153 in organic contaminant standard reference materials (SRM) 1957 and 1958. This method is simple, rapid, accurate, precise and fit for the determination of PBBs in human serum.

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Rapid determination of benzene series in seawater by gas chromatography-mass spectrometry with static headspace extraction BAI Hongyan1,2, HAN Bin1*, CHEN Junhui1, ZHENG Li1, YANG Dongfang2, WANG Xiaoru1 2012, 30 (05):  474-479.  DOI: 10.3724/SP.J.1123.2011.12042 Abstract ( 2002 )   [Full Text(HTML)] () PDF (246KB) ( 362 )   A method for the simultaneous determination of 13 benzene series (BTEX) in seawater using gas chromatography-mass spectrometry with static headspace extraction (HS-GC/MS) was developed. To carefully characterize the performance of this method, several factors affecting parameters were studied in detail, such as the type of column, heating procedure, equilibrium temperature, equilibrium time and the volume ratio of gas phase to liquid phase. The optimized conditions were as follows: the polar column of DB-WAX; heating procedure, 40 ℃ kept for 4 min, then raised to 120 ℃ at 10 ℃/min, to 180 ℃ at 25 ℃/min; equilibrium temperature, 80 ℃; equilibrium time, 10 min; and the volume ratio of gas phase to liquid phase, 1:1. Under the optimized conditions, the linear equations were obtained in the concentration range of 0.16~320 μg/L with correlation coefficients greater than 0.999. The limits of detection (S/N=3) were 0.019~0.033 μg/L. The recoveries at the three spiked levels of 1.6, 16 and 160 μg/L ranged from 81.25% to 103.73% with the relative standard deviations (RSD, n=6) from 0.3% to 4.4%. The analytical results of the practical seawater samples from Shanghai Huangpu District were satisfactory. The determination of the 13 benzene series can be finished in 12 min. The method is simple, accurate, reliable, efficient and environmental-friendly.

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Determination of 21 fragrance allergens in toys by gas chromatography-ion trap mass spectrometry LV Qing, ZHANG Qing*, BAI Hua, LI Haiyu, KANG Suyuan, WANG Chao 2012, 30 (05):  480-486.  DOI: 10.3724/SP.J.1123.2011.12005 Abstract ( 1674 )   [Full Text(HTML)] () PDF (204KB) ( 341 )   A method of gas chromatography-ion trap mass spectrometry (GC-IT-MS) was developed for the determination of 21 fragrance allergens in sticker toys, plush toys and plastic toys. The experimental conditions, such as sample pretreatment conditions, and the analytical conditions of GC-IT-MS, were optimized. The sticker toy samples and plush toy samples were extracted with acetone by ultrasonic wave, and the extracts were separated on an Agilent HP-1MS column (50 m×0.2 mm×0.5 μm), then determined by IT-MS and quantified by external standard method. The plastic toy samples were extracted by the dissolution-precipitation approach, cleaned up with an Envi-carb solid phase extraction column and concentrated by rotary evaporation and nitrogen blowing, then determined by GC-IT-MS and quantified by external standard method. The calibration curves showed good linearity in the range of 0.002~50 mg/L with the correlation coefficients greater than 0.9968. The limits of quantification (LOQ, S/N＞10) were 0.02~40 mg/kg. The average recoveries of the target compounds spiked in the sample at three concentration levels were in the range of 82.2%~110.8% with the relative standard deviations (RSDs) of 0.6%~10.5%. These results show that this method is accurate and sensitive for the qualitative and quantitative determination of the 21 fragrance allergens in the 3 types of toys.

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Preparation of new hydrophilic monolithic columns and their applications in capillary liquid chromatography and pressurized capillary electrochromatography GAO Ye, WANG Yan, WANG Chaoran, GU Xue, YAN Chao 2012, 30 (05):  487-494.  DOI: 10.3724/SP.J.1123.2011.12038 Abstract ( 2035 )   [Full Text(HTML)] () PDF (371KB) ( 288 )   New hydrophilic monolithic columns were prepared with ｛［3-(methacryloylamino)propyl］dimethyl(3-sulfopropyl)ammonium hydroxide inner salt (SPP)｝ as monomer, pentaerythritol triacrylate (PETA) as crosslinking agent, azobisisobutyronitrile (AIBN) as initiator with two different porogens consisting of ethanol/ethylene glycol and methanol/1,4-butanediol, separately. In order to obtain monolithic columns with satisfactory efficiency, electroosmotic flow (EOF) velocity and permeability, the contents of the polymerization mixture were investigated and optimized. The performances of the two columns were compared in the permeability and separation performance. It was found that the monolithic column prepared with ethanol/ethylene glycol had a better column efficiency and selectivity than that with methanol/1,4-butanediol, but was inferior to the latter in permeability. The effect of salt concentration (from 10 to 70 mmol/L ammonium formate) on the retention of nucleosides was investigated. It was observed that the retention factors of these nucleosides increased at first and then decreased. The columns were used in capillary liquid chromatography (cLC) and pressurized capillary electrochromatography (pCEC) for the separation of a test mixture of amines, phenols and nucleosides separately, and satisfactory separations for these samples were achieved. The column used in pCEC system showed better separation and higher speed of the mixture consisted of phenols and nucleosides compared to those used in cLC system.

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Capillary electrophoresis fingerprints of Baizi Yangxin Wan SUN Guoxiang*, YIN Ruijuan 2012, 30 (05):  495-500.  DOI: 10.3724/SP.J.1123.2011.12085 Abstract ( 1803 )   [Full Text(HTML)] () PDF (255KB) ( 293 )   The capillary electrophoresis fingerprint (CEFP) of Baizi Yangxin Wan (BZYXW) was established by capillary zone electrophoresis (CZE). The chromatographic fingerprint resolution index (RF) was applied to optimize the CEFP conditions. The electrophoretic separation was performed on a 75 cm (the effective length of 57 cm)×75 μm uncoated fused silica capillary with 50 mmol/L sodium borate-50 mmol/L Na2HPO4-200 mmol/L H3BO3-150 mmol/L NaHCO3 (7:7:1:1, v/v/v/v) containing 4% acetonitrile (pH 9.70) as the background electrolyte (BGE), and the BGE was chosen by using the triangular prism optimization method. The running voltage was set at 12 kV, and the detection wavelength at 228 nm. The sample solution was injected into the capillary by hydraulic pressure in 25 s. The CEFPs were produced by the electropherograms from 12 batches of BZYXW, and the 17 co-possessing peaks were selected as the fingerprint peaks of BZYXW’s CEFP by choosing ferulic acid peak as the referential peak. According to the results of classification, the reference CEFP (RCEFP) was synthesized from 12 batches of BZYXW. Taking the RCEFP for the qualified model, the systematically quantified fingerprint method(SQFM)was applied to evaluate the quality of 17 batches of BZYXW, in which the qualities of 3 batches was evaluated as good, 1 batch as fine, 3 batches as moderate, 1 batch as common, and 4 batches as inferior. The triangular prism optimization method was suggested to be good to optimize the BGE. The results showed that the BZYXW-CEFP was established with good precision and reproducibility, which can be served as a novel reference to identify and control the quality of BZYXW.

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Separation and determination of loureirin A and loureirin B in dragon’s blood by capillary zone electrophoresis YANG Xueying1, HU Xufang1, LI Fei1, WANG Xinghong2, CAO Qiue1* 2012, 30 (05):  501-506.  DOI: 10.3724/SP.J.1123.2011.12006 Abstract ( 1717 )   [Full Text(HTML)] () PDF (215KB) ( 314 )   A capillary zone electrophoresis method (CZE) for the simultaneous determination of loureirin A and loureirin B was developed based on the optimized conditions of the pH, composition and concentration of the running buffer solution. Loureirin A and loureirin B were separated and determined effectively within 15 min in a running buffer solution of 20 mmol/L Na2B4O7 (pH 9.98 adjusted with NaOH solution) containing 10.0%(v/v) acetonitrile, 5.0%(v/v) ethylene glycol and 1.0%(v/v) butanol, with the applied voltage of 20 kV, capillary temperature of 25 ℃, detection wavelength of 211 nm, and injection of 5 s at 3447 Pa. The linear ranges for the determination of loureirin A and loureirin B were 1.00~100 mg/L and 0.50~100 mg/L, respectively. The determination of loureirin A and loureirin B in dragon’s blood from natural and artificial inoculation was performed by the proposed method. The relative standard deviations for the determination of the two constituents in samples were from 0.6% to 3.8%, and the recoveries ranged between 95.1% and 105.8%. The method is simple, rapid and possesses higher reproducibility and efficiency. It can be used for the determination of loureirin A and loureirin B in dragon’s blood.

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Analysis of emodin and its metabolites based on hollow fiber liquid phase microextraction TIAN Jie2, CHEN Xuan1, BAI Xiaohong1* 2012, 30 (05):  507-514.  DOI: 10.3724/SP.J.1123.2011.12001 Abstract ( 1456 )   [Full Text(HTML)] () PDF (304KB) ( 275 )   Hollow fiber liquid phase microextraction (HFLPME) coupled with high performance liquid chromatography (HPLC) has been developed to analyze the emodin and its metabolites in plasma and urine samples. The abilities of the absorption and metabolism for the active components in traditional Chinese medicines between the male and female rats were compared, and the biological metabolism and transmutation of the analyte were detailed discussed. Emodin and its metabolites in plasma and urine samples were extracted into n-octanol (acceptor) in hollow fiber. The acceptor phase was dried and dissolved by 50 μL methanol and then analyzed by HPLC. Under the optimal conditions, the linearities of the analytes were all very good in biological samples (r＞0.9960), the detection limits of the analytes were within the ranges of 0.1~3.0 μg/L. The enrichment factors were 12.2 to 26.3. The relative standard deviations for intra-day and inter-day precision were lower than 11.0%. The average recoveries of the analytes in plasma and urine samples were all in the range of 97.9% to 103%. HFLPME-HPLC can eliminate interference from complex biological samples, improve the sensitivity and reduce the detection limit, thus this method is suitable for the determination of trace compounds in complex sample.

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Analysis of volatile compounds from Curcuma by microwave assisted solid phase headspace-gas chromatography FU Xiaohong, CHEN Hua*, YANG Fengqing, XIA Zhining 2012, 30 (05):  515-521.  DOI: 10.3724/SP.J.1123.2011.11024 Abstract ( 1966 )   [Full Text(HTML)] () PDF (253KB) ( 261 )   A novel method of microwave assisted solid phase headspace gas chromatography (MASP-HSGC) was developed through online coupling of solvent-free microwave extraction (SFME) and headspace-gas chromatography via a six-way valve. The method can quickly and directly analyze the volatile compounds from solid samples with its ability of simultaneous extraction, separation and analysis without any pretreatment. The method was applied to analyze the volatile compounds of solid Curcuma. Some experimental parameters such as the chromatographic conditions, microwave power and irradiation time were studied. Curcumol was used as the standard to evaluate the recovery, the limit of detection and the contents of compounds in a Curcuma sample. The essential oils were prepared by hydrodistillation extraction (HD) and SFME separately, and analyzed by gas chromatography-mass spectrometry (GC-MS) to compare the results with those from the developed method. It showed that the numbers of compounds obtained by the three methods of HD-GC, SFME-GC and MASP-HSGC were 35, 33, 40 respectively. The contents of curcumol using the three methods were (0.294±0.015), (0.331±0.023), (0.297±0.009) mg/g respectively. The method was approved to be suitable for the rapid analysis of volatile components in Curcuma.

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Adsorption behavior of plasmid DNA onto perfusion chromatographic matrix Miladys LIMONTA1*, Lourdes ZUMALACRREGUI2, Dayana SOLER1 2012, 30 (05):  522-526.  DOI: 10.3724/SP.J.1123.2011.11045 Abstract ( 1273 )   [Full Text(HTML)] () PDF (201KB) ( 257 )   Anion exchange chromatography is the most popular chromatographic method for plasmid separation. POROS R1 50 is a perfusion chromatographic support which is a reversed phase matrix and is an alternative to conventional ones due to its mass transfer properties. The adsorption and elution of the pIDKE2 plasmid onto reversed phase POROS R1 50 was studied. Langmuir isotherm model was adjusted in order to get the maximum adsorption capacity and the dissociation constant for POROS R1 50-plasmid DNA (pDNA) system. Breakthrough curves were obtained for volumetric flows between 0.69-3.33 mL/min, given dynamic capacity up to 2.3 times higher than those reported for ionic exchange matrix used during the purification process of plasmids with similar size to that of pIDKE2. The efficiency was less than 45% for the flow conditions and initial concentration studied, which means that the support will not be operated under saturation circumstances.

Technical Notes

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Simultaneous determination of 6 forbidden colorants in cosmetics by high performance liquid chromatography-tandem mass spectrometry LIN Weixuan1*, SUN Xingquan1, ZHAO Xuerong1, XU Wei1, GUO Guiyuan2 2012, 30 (05):  527-532.  DOI: 10.3724/SP.J.1123.2011.11049 Abstract ( 2052 )   [Full Text(HTML)] () PDF (292KB) ( 368 )   A method of high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) has been established for the simultaneous determination of six forbidden colorants including Sudan IV, Acid Violet 49, Sudan Blue 2, Solvent Red 49, Basic Violet 1 and Pigment Orange 5 in cream and powdery matrix cosmetics. The samples were extracted with ethanol-acetonitrile (3:2, v/v) solution by ultrasonic technique for 20 min, then centrifuged for purification and enriched by nitrogen blowing sequentially. The analytes were isolated on a Luna C18 column (150 mm×2.1 mm, 5 μm) by gradient elution with methanol and 10 mmol/L ammonium acetate as the mobile phases, and detected by MS/MS in the multiple reaction monitoring (MRM) mode. The qualitative analysis was based on the retention time and the relative abundance ratio of the characteristic ions, and the quantitative analysis on calibration curve method. The results showed that the limits of quantification (LOQ, S/N=10) of the six colorants ranged from 0.1 to 10 μg/kg and the average recoveries were from 86.67% to 98.22% with the relative standard deviations (RSDs) from 4.01% to 7.01%. The method is simple and rapid with high sensitivity and good reproducibility, and suitable for the determination of the six forbidden colorants in cosmetics.

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Analysis of global deoxyribonucleic acid 5-hydroxymethylcytosine in tissue by liquid chromatography-tandem mass spectrometry CHEN Liyu, ZHANG Lijian, ZHANG Liangtao, CAI Chun* 2012, 30 (05):  533-537.  DOI: 10.3724/SP.J.1123.2011.12015 Abstract ( 1851 )   [Full Text(HTML)] () PDF (163KB) ( 354 )   As preventing deoxyribonucleic acid (DNA) methylation transferase 1 (DNMT1) methylation of the target cytosine, 5-hydroxymethylcytosine could cause alterations in DNA methylation. A rapid analytical method for the determination of the degree of global DNA hydroxymethylation in tissues using liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been developed. After the extraction with phenol-chloroform, DNA was hydrolyzed to nucleobases by 88% formic acid at 140 ℃, dried under nitrogen, followed by spiking with cytosine-13C15N2 as internal standard, and reconstituted in a mixture of acetonitrile-water (9:1, v/v) for the analysis with LC-MS/MS. The LC separation was performed on a BEH HILIC column (100 mm×2.1 mm, 1.7 μm) by gradient elution with 10 mmol/L ammonium acetate and acetonitrile as mobile phases. The analytes were detected by MS/MS with positive ion electrospray ionization (ESI+) in multiple reaction monitoring (MRM) mode to satisfy qualitative and quantitative detections. The results showed that the linear range of the calibration curve for 5-hydroxymethylcytosine was 0.1~30 ng/mL, and the correlation coefficient was higher than 0.99. The limit of detection (LOD, S/N=3) and the limit of quantification (LOQ, S/N=10) were 0.057 and 0.090 ng/mL, respectively. The intraday and interday precisions were 5.13% and 6.24%, respectively. The recoveries of the spiked standards varied from 90.24% to 97.53%. The method was applied to the analysis of DNA from cerebrums of rats, and the average degree of 5-hydroxymethylcytosine was 0.66%. The method is simple, reproducible, sensitive and suitable for the quantitative analysis of 5-hydroxymethylcytosine in global DNA from tissues.

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Highly efficient and rapid capillary electrophoretic analysis of seven organic acid additives in beverages using polymeric ionic liquid as additive HAN Haifeng1,2, WANG Qing1,2, LIU Xia1*, JIANG Shengxiang1 2012, 30 (05):  538-542.  DOI: 10.3724/SP.J.1123.2011.12013 Abstract ( 1806 )   [Full Text(HTML)] () PDF (189KB) ( 338 )   A new capillary electrophoretic method for the rapid and direct separation of seven organic acids in beverages was developed, with poly(1-vinyl-3-butylimidazolium bromide) as the reliable background electrolyte modifier to reverse the direction of anode electroosmotic flow (EOF) severely. Several factors that affected the separation efficiency were investigated in detail. The optimal running buffer consisted of 125 mmol/L sodium dihydrogen phosphate (pH 6.5) and 0.01 g/L poly(1-vinyl-3-butylimidazolium bromide). Highly efficient separation (105000 to 636000 plates/m) was achieved within 4 min and standard deviations of the migration times (n=3) were lower than 0.0213 min under optimal conditions. The limits of detection （S/N=3） ranged from 0.001 to 0.05 g/L. The present method was applied to determine a beverage sample (Mirinda) for sodium citrate, benzoic acid and sorbic acid with concentration of 2.64, 0.10 and 0.08 g/L, respectively. The recoveries of the three analytes in the sample were 100.3%, 100.7% and 131.7%, respectively. The method is simple, rapid, inexpensive, and can be applied to determine organic acids as additives in beverages.

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Preparative separation of two xanthones from Halenia elliptica by high-speed counter-current chromatography LIU Yongling1,2, CHEN Tao1,2, WANG Ping1,2, YOU Jinmao1, LIU Yongjun1, LI Yulin1* 2012, 30 (05):  543-546.  DOI: 10.3724/SP.J.1123.2011.11045 Abstract ( 1587 )   [Full Text(HTML)] () PDF (162KB) ( 220 )   A high performance method for isolation and purification of two xanthones from a crude extract of Halenia elliptica was successfully established by utilizing high-speed counter-current chromatography (HSCCC). The separation was performed with a two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water (5:5:7:5, v/v/v/v) with the lower phase as the mobile phase at a flow rate of 1.5 mL/min. The apparatus was rotated at 800 r/min. The effluent was detected at 254 nm. Under the optimized conditions, 18 mg of 1-hydroxy-2,3,5-trimethoxyxanthone and 14 mg of 1-hydroxy-2,3,4,5-tetramethoxyxanthone were obtained from 100 mg of the crude extract of Halenia elliptica in one-step separation within 360 min. The results of high performance liquid chromatographic (HPLC) analysis showed that the purity of each of the target compounds was over 98%. The chemical structures of the two compounds were confirmed by 1H nuclear magnetic resonance (1H NMR) and 13C NMR. The established method is simple, highly efficient and suitable for large scale separation of xanthones from Halenia elliptica.