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Chinese Journal of Chromatography
2015, Vol. 33, No. 9
Online: 08 September 2015

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Progress in sample preparation and analytical methods for trace polar small molecules in complex samples ZHANG Qianchun, LUO Xialin, LI Gongke, XIAO Xiaohua 2015, 33 (9):  904-909.  DOI: 10.3724/SP.J.1123.2015.08012 Abstract ( 676 )   [Full Text(HTML)] () PDF (772KB) ( 193 )   Small polar molecules such as nucleosides, amines, amino acids are important analytes in biological, food, environmental, and other fields. It is necessary to develop efficient sample preparation and sensitive analytical methods for rapid analysis of these polar small molecules in complex matrices. Some typical materials in sample preparation, including silica, polymer, carbon, boric acid and so on, are introduced in this paper. Meanwhile, the applications and developments of analytical methods of polar small molecules, such as reversed-phase liquid chromatography, hydrophilic interaction chromatography, etc., are also reviewed.

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Preparation of xylitol and maltitol modified silica as novel stationary phases for hydrophilic interaction liquid chromatography and evaluation of their separation performance YONG Tian, WU Fan, XIAO Hongbin, WAN Boshun 2015, 33 (9):  910-916.  DOI: 10.3724/SP.J.1123.2015.04024 Abstract ( 688 )   [Full Text(HTML)] () PDF (855KB) ( 126 )   New types of stationary phases for hydrophilic interaction liquid chromatography (HILIC) with unique selectivity are very important for the separation of various polar and hydrophilic analytes. Two novel HILIC stationary phases based on sugar alcohol modified silica were synthesized by a simple two-step reaction in which xylitol and maltitol were bonded onto the surface of silica particles via the addition reaction between-NCO and-OH. The effect of acetonitrile content on the retention indicated that the two stationary phases were of typical HILIC character and exhibited strong retention for polar and hydrophilic analytes. They succeeded in the separation of a wide range of polar and hydrophilic analytes including water soluble vitamins, salicylic acid and its analogues, nucleic acid bases and nucleosides, and icariin and its analogues with unique selectivity. Especially, the maltitol stationary phase showed unique selectivity on glycosyl group, compared to xylitol stationary phase. Furthermore, the effects of buffer pH as well as salt concentration on the retention indicated that electrostatic interaction played an important role in the separation mechanism of the two stationary phases. For sure, the efficient stationary phases are of great potential applications in HILIC.

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Preparation and evaluation of N-acryloyltris(hydroxymethyl) aminomethane-bonded chromatographic stationary phase CHENG Xiaodong, FENG Yuqi 2015, 33 (9):  917-921.  DOI: 10.3724/SP.J.1123.2015.05006 Abstract ( 526 )   [Full Text(HTML)] () PDF (796KB) ( 114 )   The present study described the preparation of N-acryloyltris(hydroxymethyl) aminomethane-bonded silica (NAS) stationary phase based on "thiol-ene" click chemistry. The composition of the surface grafts of NAS stationary phase was determined by elemental analysis and the results demonstrated the successful introduction of the N-acryloyltris (hydroxymethyl) aminomethane groups to the silica surface. Similar elemental composition of three batches of the NAS stationary phases exhibited good reproducibility of the preparation strategy. A set of standard compounds were employed to investigate the retention mechanism of the NAS stationary phase by three different empirical equations. The results indicated the retention of the tested analytes on the NAS stationary phase was based more on a mixed-mechanism rather than a simple partitioning or adsorption process. Eight compounds were selected to study the hydrophobic and hydrophilic properties of the NAS stationary phase in mobile phase with different ACN contents. Due to its hydrophilic triolacrylamide groups and short hydrophobic alkyl chains, the NAS phase was successfully applied in both reversed-phase liquid chromatography (RPLC) mode and hydrophilic interaction liquid chromatography (HILIC) mode. The influence of flow rate on the column efficiency was compared in these two modes. In contrast to RPLC columns, the overall heights equivalent to a theoretical plate (HETP) in HILIC is weakly dependent on the retention of the analyte and the HETP curve is much flatter in RPLC than in HILIC at larger reduced velocities. Furthermore, the separation of alkylbenzenes, nucleosides and nucleobases, water-soluble vitamins was achieved on the new stationary phase, demonstrating the excellent application potential.

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Chromatographic evaluation and application of silica based azide-modified stationary phase under hydrophilic interaction liquid chromatography mode ZHAO Yanyan, LI Xiuling, GUO Zhimou, LIANG Xinmiao 2015, 33 (9):  922-928.  DOI: 10.3724/SP.J.1123.2015.03028 Abstract ( 570 )   [Full Text(HTML)] () PDF (848KB) ( 138 )   Hydrophilic interaction liquid chromatography (HILIC) has attracted more and more interests in recent years. However, the stationary phases for HILIC are still scarce. More stationary phases and separation methods should be developed. Silica based azide-modified stationary phase was synthesized and characterized by our group. The nucleosides were selected as the test samples. The retention property of nucleosides on the azide-modified stationary phase was shown with typical HILIC characterization. Moreover, the glycopeptide selectivities of azide-modified stationary phase under HILIC mode by adding two species of salts (ammonium bicarbonate and ammonium formate) and acid in mobile phase were compared. The results showed that better glycopeptide selectivity could be obtained under acid condition without adding salt in the mobile phase. With the optimized conditions, nine MS signals of glycopeptides were detected after enrichment from the tryptic digest of horseradish peroxidase (HRP). Silica based azide-modified stationary phase has the potential in further application in glycopeptide enrichment under HILIC mode.

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Evaluation of retention behavior of carbohydrate compounds on the zwitterionic hydrophilic interaction liquid chromatographic column JIANG Ge, SHEN Aijin, GUO Zhimou, LI Xiuling, LIANG Xinmiao 2015, 33 (9):  929-933.  DOI: 10.3724/SP.J.1123.2015.05011 Abstract ( 746 )   [Full Text(HTML)] () PDF (885KB) ( 153 )   Because of the strong polarity of carbohydrate compounds which have weak retention in reverse-phase liquid chromatography (RPLC), hydrophilic interaction liquid chromatography (HILIC) is suitable for the separation and analysis of the carbohydrate compounds. In this study, nine carbohydrate compounds were selected as the test probes to systematically evaluate the retention behavior of the carbohydrate compounds on a Click TE-Cys column with zwitterionic stationary phase. And the effects of the ratio of organic phase and salt concentration in mobile phase on the retention behavior were investigated as well. The experiments proved that the nine carbohydrate compounds could be eluted in the order of their polarities from the Click TE-Cys column. With the increase of organic phase ratio, the retention of carbohydrate compounds was enhanced. As the increase of salt concentration, the retention of the carbohydrate compounds increased except sialic acid. Using displacement-adsorption liquid phase interaction model to simulate the retention behavior of the carbohydrate compounds under HILIC, the retention behavior of HILIC was described by the retention equation of ln k=a+bln CB+cCB, and the retention values of HILIC were analyzed by multiple linear regression. The results demonstrated that the retention behavior of carbohydrate compounds on the Click TE-Cys was in accordance with the retention regularity of HILIC.

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Deep eutectic solvent: a new kind of mobile phase modifier for hydrophilic interaction liquid chromatography TAN Ting, QIAO Xin, WAN Yiqun, QIU Hongdeng 2015, 33 (9):  934-937.  DOI: 10.3724/SP.J.1123.2015.05002 Abstract ( 889 )   [Full Text(HTML)] () PDF (749KB) ( 214 )   Deep eutectic solvents (DESs) were used as a new kind of mobile phase modifier in hydrophilic interaction liquid chromatography (HILIC). In our experiment, a SiO2 column (150 mm×4.6 mm, 3 μm) was selected to separate several nucleobases and nucleosides by using the mixed solution of acetonitrile and DES (choline chloride-ethylene glycol (1:3, mol/mol)) as mobile phase. Subsequently, the concentrations of DESs in acetonitrile and the column temperature on the effect of separation were investigated. According to the experimental results, better separation of nucleobases and nucleosides was obtained by using acetonitrile and DESs mixed solution as mobile phase than that using traditional water-based solution. For example, a baseline separation between cytosine and cytidine cannot be achieved by HILIC with water-based mobile phase, however, greater improvement was gained by HILIC with modified DES-acetonitrile mobile phase. Meanwhile, the retention times of nucleobases and nucleosides decreased as the proportion of DESs in acetonitrile increased, the most significant decrease of which was with cytidine. Similar retention behavior took place with the effect of column temperature. Decreased retention times of the analytes were observed as column temperature increased. The experimental results indicated that this new method may solve some separation difficulties in traditional water-based HILIC, which also successfully verify the feasibility of DESs as mobile phase modifiers.

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Quantitative analysis of five antiviral drugs by hydrophilic interaction liquid chromatography-charged aerosol detection LONG Zhen, JIN Yan, LIU Xiaoda, GUO Zhimou, SHEN Aijin, HU Xingjuan, WU Ningpeng 2015, 33 (9):  938-942.  DOI: 10.3724/SP.J.1123.2015.03031 Abstract ( 555 )   [Full Text(HTML)] () PDF (787KB) ( 151 )   Antiviral drugs are widely used for human and animals. However, the analysis of the mixture of antiviral drugs is a challenge for high performance liquid chromatography, since some of the antiviral drugs have weak UV absorbance and poor retention in reversed phase liquid chromatography. A method of hydrophilic interaction liquid chromatography-charged aerosol detection (HILIC-CAD) was optimized for the qualitative and quantitative analysis of five antiviral drugs. In this study, Click TE-Cys was used as the stationary phase and CAD was used as the detector. Various chromatographic conditions including the kind of detector, chromatographic mode, column and mobile phase composition were investigated. Compared to UV-Vis, more antiviral drugs could be detected by CAD, since it is a universal detector. HILIC mode is an alternative to reversed phase liquid chromatography mode. HILIC provides higher sensitivity and unique selectivity to target compounds. After the optimized parameters were obtained, the developed method was used for the quantitative analysis of the five antiviral drugs. As a result, the current method has good repeatability, a wide linear range (0.07-2.28 mg/mL) and good sensitivity (LOQ≤0.04 mg/mL). The RSDs of intra-day and inter-day peak areas were less than 3.06% and 5.38% respectively. The above results demonstrated that the current method is sensitive, robust and effective for the separation and determination of these five antiviral drugs.

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Determination of L-carnitine in milk and dairy products by hydrophilic liquid chromatography-tandem mass spectrometry LIU Yanming, XUE Xia, LIU Guoqiang, REN Xuemei, HU Mei, ZHU Jianhua 2015, 33 (9):  943-945.  DOI: 10.3724/SP.J.1123.2015.04003 Abstract ( 825 )   [Full Text(HTML)] () PDF (728KB) ( 138 )   An analytical method was developed for the determination of L-carnitine in milk and dairy products using hydrophilic interaction chromatography-tandem mass spectrometry (HILIC-MS/MS). The samples were extracted with 2%(v/v) acetic acid solution, and the protein was precipitated with acetonitrile subsequently. The separation of L-carnitine was carried out on an Acquity UPLC BEH HILIC column using ammonium acetate and acetonitrile as mobile phases. The quantification analysis of the target compound was performed under multiple reaction monitoring (MRM) mode by external standard method. A good linear relationship was obtained between the peak area and concentration of L-carnitine in the range of 1-100 μg/L with the correlation coefficient more than 0.99. The limit of quantification (LOQ) of L-carnitine was 0.01 mg/kg. The spiked recoveries were 96.0%-103.4%. The precisions (RSDs) were 1.2%~4.3%. The sample preparation was simple and rapid, and the results were precise and sensitive. The developed method is suitable for the study of concentration of L-carnitine in milk and dairy products, and the technical support for the infant formula is provided.

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Analysis of carbapenems by hydrophilic interaction chromatography and its application ZHU Yinfang, JI Shunli, LI Shaohui, LI Cheng, ZHANG Feifang, LIANG Xinmiao 2015, 33 (9):  946-950.  DOI: 10.3724/SP.J.1123.2015.05005 Abstract ( 490 )   [Full Text(HTML)] () PDF (786KB) ( 109 )   A hydrophilic interaction chromatographic (HILIC) method has been developed for the determination of the four carbapenems in human urine and tap water. The parameters including acetonitrile amount, buffer concentration and pH on the retention behavior of the four carbapenem antibiotics on an XAmide column were explored and the possible HILIC retention mechanism was proposed. Good linearities were obtained over the mass concentration ranges of 0.1-250 mg/L for biapenem, doripenem and ertapenem with correlation coefficients (R2)=0.9999 and while it was 0.5-250 mg/L with R2=0.9998 for meropenem. The limits of quantification (LOQs) of all carbapenems were 0.1-0.5 mg/L. The spiked recoveries were within 100.4%-111.9% (RSD< 1%) for urine samples and 79.6%-107.4% (RSD< 5%) for tap water samples all at the spiked levels of 5 mg/L and 25 mg/L. The proposed method is accurate, sensitive, simple and suitable for the determination of the four carbapenems in human urine samples and tap water samples.

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Analysis of vancomycin and its related impurities by hydrophilic interaction liquid chromatography YAN Jingyu, GUO Zhimou, DING Junjie, SHEN Aijin, WANG Jixia, JIN Gaowa, LIANG Xinmiao 2015, 33 (9):  951-956.  DOI: 10.3724/SP.J.1123.2015.05032 Abstract ( 950 )   [Full Text(HTML)] () PDF (834KB) ( 188 )   The current reversed-phase liquid chromatography as the main analytical method for vancomycin is inappropriate due to its poor polarity selectivity and mass spectrometry compatibility. Hydrophilic interaction chromatography (HILIC) method has been verified to provide the glycopeptide substances with good retention and polarity selectivity, therefore, an HILIC method was developed for the analysis of vancomycin and its related impurities including norvancomycin, desvancosaminyl vancomycin, dedichloro vancomycin and crystalline degradation product (CDP-1). In this work, a systematic evaluation of retention behavior of vancomycin and its related impurities in hydrophilic interaction chromatography was performed and the influences of stationary phase, acetonitrile content, buffer salt and pH of mobile phase were studied. According to the results, Click XIon column was selected as stationary phase and ammonium formate was additive in the mobile phase. Vancomycin and its related impurities were totally separated under the optimization conditions. It is concluded that hydrophilic interaction chromatography may be a new strategy for the separation of vancomycin and its structural analogues.

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Preparation of surface molecularly imprinted polymers for penicilloic acid and its adsorption properties ZHENG Penglei, LUO Zhimin, CHANG Ruimiao, GE Yanhui, DU Wei, CHANG Chun, FU Qiang 2015, 33 (9):  957-965.  DOI: 10.3724/SP.J.1123.2015.04036 Abstract ( 691 )   [Full Text(HTML)] () PDF (2210KB) ( 140 )   On account of the specificity and reproducibility for the determination of penicilloic acid in penicillin, this study aims to prepare penicilloic acid imprinted polymers (PEOA-MIPs) by surface polymerization method at the surface of modified silica particles by using penicilloic acid (PEOA) as the template molecule, methacrylic acid (MAA) as the functional monomer, ethylene glycol dimethacrylate (EGDMA) as the cross linker, and methanol/acetonitrile as the solvents. The synthesis conditions were optimized, and PEOA-MIPs had the best adsorption capacity when the molar ratio of template molecule/functional monomer was 1:4, cross linking degree was 85% and the solvent ratio of methanol/acetonitrile was 1:1 (v/v). The adsorption properties were evaluated by adsorption experiments, including the adsorption isotherms, kinetics and selectivity. The adsorption process between PEOA-MIPs and PEOA fitted the Langmuir adsorption isotherm with the maximum adsorption capacity of 122.78 mg/g and the pseudo-second-order reaction kinetics with fast adsorption kinetics (the equilibrium time of 45 min). The as-synthesized PEOA-MIPs were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and thermal gravimetric analysis (TGA). The results indicated that the MIPs layer has been successfully grafted on the surface of SiO2 microparticles and the PEOA-MIPs had the excellent thermal stability. The PEOA-MIPs showed the highest selective recognition for PEOA. The PEOA-MIPs possess a high adsorption capacity, rapid mass-transfer rate and high selectivity to PEOA when compared with non-imprinted polymers (PEOA-NIPs). The PEOA-MIPs was expected to be used as the solid phase extraction medium and this study provides the potential applications for fast recognition and analysis of the penicilloic acid in penicillin.

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Using liquid chromatography-mass spectrometry based metabolomics to discriminate between cold pressed rice bran oils produced from two different cultivars of Oryza sativa L. ssp. indica in Thailand Tossaton CHAROONRATANA, Thanapat SONGSAK, Apirak SAKUNPAK, Pathamaporn PATHOMPAK, Laksana CHAROENCHAI 2015, 33 (9):  966-973.  DOI: 10.3724/SP.J.1123.2015.04006 Abstract ( 554 )   [Full Text(HTML)] () PDF (689KB) ( 170 )   A newly developed liquid chromatography-mass spectrometry (LC-MS) method for the analysis of cold pressed rice bran oil (RBO) was established and used to discriminate between RBOs produced from two different cultivars of major Thai fragrant rice species. The cold pressed RBO was prepared using the screw compression method. The LC-MS data were preprocessed with MZmine 2.10 program before evaluating with principal component analysis using SIMCA 13 software. The LC-MS method was able to detect and quantify several kinds of valuable constituents such as fatty acids, vitamin E, and γ-oryzanol. The chromatographic condition was feasible; short time for analysis and simple method were achieved. From score plot and loading plot of principle component analysis (PCA), two rice cultivar samples were clearly separated, and it was revealed that Khao-Hom-Pathum was more suitable than Khao-Hom-Mali for cold pressed RBO production since it contained high total γ-oryzanol and less saturated free fatty acids. As with the fixed price of all the rice brans, this information can be used in order to, if possible, preserve the price of rice brans from different cultivars.

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Determination of flavonol glycosides in tea samples by ultra-high performance liquid chromatography-photodiode array detection-tandem mass spectrometry WANG Zhicong, SHA Yuebing, YU Xiaobo, LIANG Yuerong 2015, 33 (9):  974-980.  DOI: 10.3724/SP.J.1123.2015.04028 Abstract ( 771 )   [Full Text(HTML)] () PDF (1362KB) ( 156 )   An ultra-high performance liquid chromatography-photodiode array detection-tandem mass spectrometry (UPLC-PDA-MS/MS) method was developed for the determination of flavonol glycosides in tea samples. The chromatographic separation was performed on an UPLC HSS T3 column by gradient elution with the mobile phases of acetonitrile and water both containing 0.1%(v/v) formic acid. A total of 15 flavonol glycosides which include 3 myricetin glycosides, 6 quercetin glycosides and 6 kaempferol glycosides were positively identified in green and black tea samples by comparing the retention times and mass spectra of the samples with standards and publications. The quantities of flavonol glycosides were relatively calculated with the standard quercetin-3-rhamnosylglucoside (Q-GRh) which was calibrated with external quantification method using multi-reaction monitoring (MRM) mode. The results showed that there were different flavonol glycoside distributions in green tea and black tea. The total amount of flavonol glycosides in green tea was 1.7 times of that in black tea. The major flavonol glycosides in green tea were myricetin-3-galactoside (M-Ga), myricetin-3-glucoside (M-G), quercetin-3-glucosyl-rhamnosyl-galactoside (Q-GaRhG), quercetin-3-glucosyl-rhamnosyl-glucoside (Q-GRhG), kaempferol-3-glucosyl-rhamnosyl-galactoside (K-GaRhG) and kaempferol-3-glucosyl-rhamnosyl-glucoside (K-GRhG), but for black tea, the major flavonol glycosides were quercetin-3-rhamnosylglucoside (Q-GRh), quercetin-3-glucoside (Q-G), kaempferol-3-rhamnosylglucoside (K-GRh) and kaempferol-3-galactoside (K-Ga). The present method is accurate, convenient for the rapid identification of flavonol glycosides and analysis of constituent distribution for green and black teas.

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Determination of L-dopa and dopamine in rat brain microdialysate by ultra high performance liquid chromatography-tandem mass spectrometry using stable isotope-coded derivatization coupled with dispersive liquid-liquid microextraction QI Weimei, ZHAO Xian-en, QI Yong, SUN Zhiwei, CHEN Guang, YOU Jinmao, SUO Yourui 2015, 33 (9):  981-987.  DOI: 10.3724/SP.J.1123.2015.04049 Abstract ( 818 )   [Full Text(HTML)] () PDF (1252KB) ( 202 )   The sensitive detection method of levodopa (L-DOPA) and dopamine (DA) in rat brain microdialysate of Parkinson's disease (PD) is an essential tool for the clinical study and attenuated synergistic drug screening for L-DOPA from traditional Chinese medicines. Using d0/d3-10-methyl-acridone-2-sulfonyl chloride (d0/d3-MASC) as stable isotope derivatization reagent, a novel ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was developed and validated for L-DOPA and DA by stable isotope-coded derivatization coupled with ultrasonic-assisted dispersive liquid-liquid microextraction (UA-DLLME). d0-MASC (light) and d3-MASC (heavy) were used as derivatization reagents for microdialysate samples and standards, respectively. Mixtures of the two solutions were prepared by UA-DLLME for UHPLC-MS/MS analysis with multiple reaction monitoring (MRM) mode. With d3-MASC heavy derivatives as internal standards for corresponding light derivatives from samples, the stable isotope internal standard quantification for L-DOPA and DA was carried out. The stable derivatives were obtained in aqueous acetonitrile (pH 10.8 sodium carbonate-sodium bicarbonate buffer) at 37 ℃ for 3.0 min, and then were separated within 2.0 min using gradient elution. Linear range was 0.20-1500.0 nmol/L (R> 0.994). LODs were 0.005 and 0.009 nmol/L for DA and L-DOPA (S/N=3), respectively. This method was validated, and it showed obvious advantages in comparing with the reported methods in terms of sensitivity, analysis speed and anti-matrix interference. This method has been successfully applied to the study of effect of Shouwu Fang on L-DOPA and DA concentration fluctuations in PD rat brain microdialysate.

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Pressure-assisted electrokinetic injection stacking for citalopram drug to achieve highly sensitive detection and enantioseparation by capillary electrophoresis XU Zhongqi, YE Feng, WANG Yongle, LI Aimei 2015, 33 (9):  988-994.  DOI: 10.3724/SP.J.1123.2015.03038 Abstract ( 529 )   [Full Text(HTML)] () PDF (1303KB) ( 105 )   Pressure-assisted electrokinetic injection (PAEKI) was applied to the highly sensitive enantioseparation of the positively charged drug citalopram (CIT) by capillary electrophoresis (CE). It was found that the injection discrimination occurred in electrokinetic injection (EKI) process due to the different dynamic equilibrium constant between chiral selector (sulfated-β-cyclodextrin, S-β-CD) and two isomers of CIT. Herein, it was proposed to use the background electrolyte (BGE) without chiral selector to fill the capillary, and then start the EKI step to eliminate the injection discrimination of free analytes. The critical parameters in PAEKI could be optimized in two steps to seek the balance between the electroosmotic flow (EOF) and the counterbalance pressure. Under the optimized PAEKI conditions (+10 kV, 0.2 psi (ca. 1.4 kPa)), the obtained LODs (S/N=3) of the two isomers were 1.1 and 2.2 ng/mL under UV detection (205 nm), which was averaged 62-fold improved in comparison with normal hydrodynamic injection (HDI). The proposal offered ng/mL (ppb) level sensitivity of CIT determination and could be an effective method in the applications in human body biofluids.

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Determination of 35 antibiotic residues of tetracyclines, sulfonamides, penicillins, macrolides and amphenicols in milk by liquid chromatography-tandem mass spectrometry WANG Hao, ZHAO Li, YANG Hongmei, PAN Hongyan, SHI Hailiang, QIAN Cong, ZHANG Shan 2015, 33 (9):  995-1001.  DOI: 10.3724/SP.J.1123.2015.04046 Abstract ( 817 )   [Full Text(HTML)] () PDF (782KB) ( 308 )   A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was established for the simultaneous determination of 35 antibiotic residues of tetracyclines, sulfonamides, penicillins, macrolides and amphenicols in milk. The samples were extracted with alkaline acetonitrile and Mcllvaine buffer solution under ultrasonication. The separation of target compounds was performed on an Eclipse XDB-C8 column (150 mm×2.1 mm, 3.5 μm) with gradient elution at a flow rate of 0.25 mL/min, and with an injection volume of 10 μL. The identification and quantification of the compounds were completed by liquid chromatography-tandem mass spectrometry in multiple reaction monitoring (MRM) mode. The limits of detection were all below 10.0 μg/kg. The average spiked recoveries of the method ranged from 70.1% to 109.9% with relative standard deviations (RSDs) of 2.89%-9.99%. After validation, the method was applied to the analysis of antibiotic residues in milk products in China. Fifty samples were screened under the well defined methodology, and the results showed that chloramphenicol, only in one sample, was monitored with the content of 0.48 μg/kg. A risk of contamination of milk with chloramphenicol has been determined to exist. Therefore this method is convenient, rapid, sensitive and reliable, and can be successfully applied to the simultaneous detection of the 35 antibiotic residues of tetracyclines, sulfonamides, penicillins, macrolides and amphenicols in milk.

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Simultaneous determination of multi-classes of veterinary drug residues in pork by ultra performance liquid chromatography coupled with quadrupole-time of flight mass spectrometry ZHU Wanyan, ZHANG Xin, YANG Juan, XU Wenyuan, XU Meiling 2015, 33 (9):  1002-1008.  DOI: 10.3724/SP.J.1123.2015.04033 Abstract ( 585 )   [Full Text(HTML)] () PDF (1113KB) ( 156 )   An analytical method was established for the simultaneous determination of six classes of 33 veterinary drug residues in pork by ultra performance liquid chromatography coupled with quadrupole-time of flight mass spectrometry (UPLC-Q-TOF MS). The QuEChERS method has been validated for the extraction. In this method, the sample was extracted by acetonitrile containing 5%(v/v) acetic acid and cleaned-up with C18 and NH2 adsorbents. The extract was measured directly by UPLC-Q-TOF MS with electrospray ionization in positive mode. The compounds were separated on a ZORBAX SB-C18 column (100 mm×2.1 mm, 3.5 μm) with acetonitrile-0.1% formic acid containing 5 mmol/L ammonium acetate as mobile phases under gradient elution. The confirmatory analysis was carried out by determining the retention times and accurate masses of all the compounds and fragment ions upon Target MS/MS. The correlation coefficients of the 33 veterinary drugs were more than 0.99 within their linear ranges. The limits of quantification (LOQs) were 2.5-100 μg/kg. The recoveries ranged from 67.0% to 109.0% with the relative standard deviations (RSDs, n=6) not more than 15.1%. The method is rapid, sensitive, and suitable for the simultaneous determination of multi-classes of veterinary drugs in pork.

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Separation of C5-C7 hydrocarbon components on Al2O3 capillary column and its application LI Jiwen, JIANG Liyan, LIU Junyan, WANG Chuan 2015, 33 (9):  1009-1014.  DOI: 10.3724/SP.J.1123.2015.03027 Abstract ( 560 )   [Full Text(HTML)] () PDF (797KB) ( 117 )   The separation and qualitative analysis of 54 common C5-C7 hydrocarbon components on three Al2O3 capillary columns, including S type, KCl type and M type, were investigated in detail. The results showed that the separation of the 54 C5-C7 hydrocarbon components were partly different on these three Al2O3 capillary columns, and the most of C5-C7 hydrocarbon components could be well separated, except that some of them couldn't achieve a baseline separation or co-eluted. Linear temperature programmed retention indices of the 54 C5-C7 hydrocarbon components, including 15 C5 hydrocarbons, 25 C6 hydrocarbons and 14 C7 hydrocarbons, were determined on these three Al2O3 capillary columns. The determination of linear temperature programmed retention indices for these C5-C7 hydrocarbon components on Al2O3 capillary columns provided a basis for the qualitative analysis of them. At the same time, a real pyrolysis gas sample from one of the petrochemical plants was qualitatively analyzed according to the linear temperature programmed retention indices, and the contents of C5-C7 hydrocarbon components were determined. The application field of Al2O3 capillary column was expanded and it is helpful for the analysis of light hydrocarbons in petrochemical enterprises.