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Chinese Journal of Chromatography
2017, Vol. 35, No. 11
Online: 08 November 2017

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Preparation and evaluation of multidentate ligand-bonded silica chromatographic medium CHEN Bin, ZHANG Ning, LI Rong, LI Chen, FAN An 2017, 35 (11):  1113-1119.  DOI: 10.3724/SP.J.1123.2017.07018 Abstract ( 402 )   [Full Text(HTML)] () PDF (938KB) ( 87 )   Iminodisuccinic acid (IDS), a green environment-friendly multidentate chelating agent, was used as a ligand to synthesize IDS-Silica stationary phase under the optimized conditions. The binding capacity of IDS on the stationary phase was measured by potentiometric titration. The chromatographic properties and metal chelating property on IDS-Silica column were investigated. Three standard protein mixtures were separated successfully with IDS-Silica column. The results showed that the IDS-Silica column displayed a typical cation exchange property. The binding characteristics of six different metal ions on IDS-Silica stationary phase were examined by inductively coupled plasma-atomic emission spectroscopy (ICP-AES). The results validated that the variation of binding capacities of metal ions on the stationary phase were consistent with the chelating stability order of the IDS-Silica column for metal ions. Compared with the other silica columns bonded with the three different aminocarboxyl ligands, the bonding amounts of Cu2+ on IDS-Silica column was the largest, which indicated that IDS had stronger chelating ability for metal ions. This characteristic lays the foundation for IDS as a good chromatographic packing used in the field of immobilized metal affinity chromatography (IMAC), thus probably provides an effective solution to reduce the leaking problem of metal ion from IMAC column during protein elution with one competitive agent.

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Preparation and investigation of novel pyrrolidinium-bonded stationary phase for reversed-phase high-performance liquid chromatography Elahe NAGHDI, Kourosh TABAR HEYDAR, Ali SHARIFI, Seyyed Hamid AHMADI 2017, 35 (11):  1120-1128.  DOI: 10.3724/SP.J.1123.2017.07008 Abstract ( 404 )   [Full Text(HTML)] () PDF (691KB) ( 83 )   A new ionic liquid-based high-performance liquid chromatography stationary phase is reported. A derivative of N-methyl pyrrolidinium tetrafluoroborate was covalently immobilized on the surface of silica particles to prepare silica-based N-methyl pyrrolidinium tetrafluoroborate (SilprMP BF4) stationary phase. The obtained ionic liquid-modified silica was evaluated and confirmed by elemental analysis, infrared spectroscopy, and thermogravimetric analysis. A column was packed with the modified particles. The retention behavior of aromatic compounds, alkyl benzenes, and acidic and basic compounds on the SilprMP BF4 stationary phase was studied under reversed-phase liquid chromatography conditions. The effect of the eluent pH on the separation of the acidic and basic compounds was also studied. The new stationary phase involves multiple retention mechanisms, such as electrostatic, hydrophobic, ion-dipole, and anion-exchange interactions, which might lead to multipurpose separation media.

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Rapid determination of 55 fungicides in siraitia grosvenoriis by QuEChERS and high performance liquid chromatography-tandem mass spectrometry QIN Fu, DENG Quandao, LI Yong, HUANG Daxin, WANG Wenlong 2017, 35 (11):  1129-1136.  DOI: 10.3724/SP.J.1123.2017.07019 Abstract ( 526 )   [Full Text(HTML)] () PDF (3417KB) ( 119 )   A method for the determination of 55 fungicides in siraitia grosvenoriis by QuEChERS and high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was established. The samples were extracted with acetonitrile containing 1%(v/v) acetic acid, then dehydrated by anhydrous magnesium sulfate and purified by anhydrous sodium sulfate, N-propyl ethylenediamine (PSA) and C18. Then, 95% (v/v) acetonitrile aqueous solution (organic phase) and water (aqueous phase), both containing 0.005 mol/L ammonium formate and 0.01% (v/v) formic acid, were used as mobile phases with gradient elution. The compounds were tested by positive electrospray ion source (ESI+) and dynamic multiple reaction monitoring (DMRM) mode. Fifty-five fungicides were quantified by external standard method considering matrix effects. The correlation coefficients (R2) were greater than 0.99, which indicated that the linear dependence of the 55 fungicides were good in the range of 1.0-100.0 μg/kg. The LODs (S/N>3) and LOQs (S/N>10) of all the fungicides were 1.0 μg/kg and 10.0 μg/kg, respectively. The recoveries were in the range of 76.96%-118.45% and the relative standard deviations (RSDs) ranged from 3.44% to 19.63% (n=6). This method has the advantages of rapidity, accuracy and sensitivity for the high-throughput detection of fungicides residues in siraitia grosvenoriis.

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Fast determination of pericarpium papaveris illegally added in foods by TurboFlow online purification-ultra performance liquid chromatography-triple quadrupole/linear ion trap mass spectrometry ZHANG Xiuyao, CAI Xinxin, ZHANG Xiaoyi, LI Ruifen 2017, 35 (11):  1137-1144.  DOI: 10.3724/SP.J.1123.2017.06027 Abstract ( 478 )   [Full Text(HTML)] () PDF (1326KB) ( 165 )   A fast confirmation method was developed for the determination of the six markers of pericarpium papaveris, morphine, codeine, narcotine, papavarine, thebaine and protopine in foods, by TurboFlow online purification-ultra performance liquid chromatography-triple quadrupole/linear ion trap mass spectrometry (TF-UPLC-QTRAP MS). The sample was extracted with 0.10 mol/L HCl. After the procedure of removal of lipid with hexane, the extraction solution was analyzed by TF-UPLC-QTRAP MS. The main factors influencing the purification efficiency including TurboFlow column, mobile phase and elution solution were optimized. The six opium alkaloids were detected by positive electrospray ionization tandem mass spectrometry in the multiple reaction monitoring-information-dependent acquisition-enhanced product ion (MRM-IDA-EPI) mode, and quantified by solvent standard internal standard method. The limits of detection were 0.05-0.5 μg/kg and the limits of quantification were 0.2-2 μg/kg for the six opium alkaloids. The recoveries were in the range of 81.1%-98.6% with the relative standard deviations ranging from 2.9% to 15.7% (n=6). The method is sensitive and accurate, and has been successfully applied to the detection of pericarpium papaveris illegally added in foods.

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Determination of six allergenic coumarin compounds in children's toys using hollow-fiber liquid-phase microextraction followed by ultra-performance liquid chromatography-tandem mass spectrometry HU Mingzhu, LIAN Xianhui, LIU Han, GUO Xiangyu, LÜ Yueguang, BAI Hua, XUE Hongyu, MA Qiang 2017, 35 (11):  1145-1151.  DOI: 10.3724/SP.J.1123.2017.08011 Abstract ( 410 )   [Full Text(HTML)] () PDF (1032KB) ( 114 )   A comprehensive analytical method was developed for the determination of six allergenic coumarin compounds (coumarin, 7-methyl coumarin, 7-methoxycoumarin, 7-ethoxy-4-methyl coumarin, 4,6-dimethyl-8-tert-butyl coumarin and hexahydrocoumarin) in children's toys based on hollow-fiber liquid-phase microextraction (HF-LPME) followed by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). HF-LPME was employed in sample pretreatment with the following parameters:extraction solvent of n-octanol, stirring rate of 700 r/min, extraction time of 50 min and amount of sodium chloride of 0.7 g. After chromatographic separation on an ACQUITY UPLC BEH Phenyl column (150 mm×2.1 mm, 1.7 μm), the target compounds were analyzed under multiple reaction monitoring (MRM) mode in positive electrospray ionization mode. The limits of quantification (LOQs) of the six allergenic coumarin compounds were either 2 μg/kg (7-ethoxy-4-methyl coumarin and 4,6-dimethyl-8-tert-butyl coumarin) or 10 μg/kg (coumarin, hexahydrocoumarin, 7-methyl coumarin and 7-methoxycoumarin). The average recoveries at different spiked levels ranged from 70.8% to 118.9% with relative standard deviations (RSDs) of 0.19%-16.34% (n=6). The proposed method is accurate, sensitive, reliable, and can be applied for the inspection and quality control of toy products.

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High sensitive non-derivative determination of cyclovirobuxin D by high-performance liquid chromatography-electrochemical determination LONG Zhen, GAMACHE Paul, GUO Zhimou, PAN Yuanyuan, RAN Liangji, LIU Xiaoda, JIN Yan, LIU Xingguo, LIU Lüye, LIANG Lina 2017, 35 (11):  1152-1159.  DOI: 10.3724/SP.J.1123.2017.07020 Abstract ( 356 )   [Full Text(HTML)] () PDF (852KB) ( 139 )   A high-performance liquid chromatography-electrochemical detection (HPLC-ECD) method was developed to determine cyclovirobuxin D (CVB-D) levels in tablets and human blood samples. A column with a positive charge-modified C18 stationary phase, C18HCE, was selected to analyze CVB-D, because it provided a sharper and more symmetric peak for CVB-D than conventional C18 stationary phase. Two types of working electrode materials, glassy carbon (GC) and boron-doped diamond (BDD), were evaluated. BDD was found to provide better sensitivity than GC owing to its lower background current and baseline noise. Utilizing the BDD electrode, C18HCE column, and optimized mobile phase composition, the developed HPLC-ECD method showed a much better sensitivity. The limit of detection and limit of quantification of the HPLC-ECD method for CVB-D were 0.198 and 0.297 μg/L, respectively. It was approximately 12727, 11481, and 2630 times more sensitive than ultraviolet (UV), evaporative light scattering detection, and charged aerosol detection, respectively. The sensitivity of the developed HPLC-ECD method was comparable or even better (16.8 times) than reported mass spectrometry (MS) methods for the determination of CVB-D. Additionally, it offered a much wider linear dynamic range (up to 4 orders of magnitude, 0.297-1891 μg/L) and was much less complicated than MS methods for determination of CVB-D. The developed HPLC-ECD method can be used for determination of CVB-D at both high and low concentrations. Good intra-day (relative standard deviation (RSD) of peak area<5.08%) and inter-day (RSD of peak area<5.57%) reproducibilities of the developed HPLC-ECD method were obtained even for a low mass concentration (59.1 μg/L) sample. After the optimized parameters were acquired, this method was applied to the quantitative analysis of CVB-D in CVB-D tablets and human blood samples. With a slight modification, the current HPLC-ECD method can also be applied to analyze many other basic compounds including basic drugs and environmental pollutants.

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Determination of patulin in fruits and jam by solid phase extraction-ultra performance liquid chromatography LÜ Weichao, SHEN Shuchang, WANG Chao 2017, 35 (11):  1160-1164.  DOI: 10.3724/SP.J.1123.2017.07005 Abstract ( 442 )   [Full Text(HTML)] () PDF (765KB) ( 124 )   With magnesium silicate, silica gel, diatomite and calcium sulfate as raw materials, a new solid phase extraction column was prepared through a series of processes of grinding to ethanol homogenate, drying and packing into polypropylene tube. The sample was hydrolyzed by pectinase, extracted by acetonitrile and purified by solid phase extraction. The target compounds were separated on a C18 column (100 mm×2.1 mm, 1.8 μm), using 0.8% (v/v) tetrahydrofuran solution as mobile phase with a flow rate of 0.5 mL/min. The detection wavelength was 276 nm. The effect of pectinase on extraction yield and purification effect of solid-phase extraction column were investigated. The optimum chromatographic conditions were selected. There was a good linear relationship between the peak heights and the mass concentrations of patulin in the range of 0.1 to 10 mg/L with the correlation coefficient (R2) of 1. The limit of detection for this method was 10.22 μg/kg. The spiked recoveries of samples were 86.58%-94.84% with the relative standard deviations (RSDs) of 1.45%-2.28%. The results indicated that the self-made solid phase extraction column had a good purification efficiency, and the UPLC had a high separation efficiency. The method is simple, accurate and of great significance for the quality and safety control of fruit products.

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Determination of iminodiacetic acid and glycine in dehydrogenation products of diethanolamine by pre-column derivatization and high performance liquid chromatography ZHANG Lei, DUAN Zhengkang, ZHU Hongwen, YIN Ke 2017, 35 (11):  1165-1170.  DOI: 10.3724/SP.J.1123.2017.08006 Abstract ( 487 )   [Full Text(HTML)] () PDF (811KB) ( 116 )   An analytical method was developed for the determination of iminodiacetic acid (IDA) and glycine (Gly), the dehydrogenation products of diethanolamine, by high performance liquid chromatography (HPLC) coupled with pre-column derivatization using p-toluenesulfonyl chloride (PTSC) as the derivatization reagent. IDA and Gly reacted with PTSC in the alkaline environment (pH 11) under 45℃ for 15 min. Then the derivatization products were analyzed by HPLC-MS. The separation was carried out on a high performance liquid chromatograph equipped with an ultraviolet detector. A VP-ODS column (200 mm×4.6 mm, 5 μm) was employed using 0.03 mol/L ammonium acetate (pH 5.5)-acetonitrile (87:13, v/v) as mobile phases for isocratic elution at a flow rate of 1 mL/min and detection wavelength of 235 nm. The results showed good linearities for iminodiacetic acid of 900-2100 mg/L, and for glycine of 20-100 mg/L, respectively. The linear correlation coefficients (R2) were both greater than 0.999. The limits of detection (LODs) of IDA and Gly were 0.0897 mg/L and 0.0262 mg/L and the recoveries were in the range of 98.7%-99.3% and 98.0%-99.5%, respectively. The relative standard deviations (RSDs) of IDA and Gly were in the range of 0.89%-1.23% and 0.95%-1.11% (n=3). The method has the characteristics of mild reaction conditions and high accuracy, and is well suitable for the determination of IDA and Gly in industrial production.

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Determination of 18 polychlorinated biphenyls in camellia seeds by multiple vortex and gas chromatography-triple quadrupole mass spectrometry SHEN Danyu, YUAN Xinyue, ZHANG Yanping, HANan Yongxiang, LIU Yihua, MO Runhong, ZHONG Donglian, TANG Fubin 2017, 35 (11):  1171-1176.  DOI: 10.3724/SP.J.1123.2017.07023 Abstract ( 394 )   [Full Text(HTML)] () PDF (2458KB) ( 113 )   A method based on the cleaning effects of different sorbents and gas chromatography-triple quadrupole mass spectrometry (GC-QQQ-MS/MS) was developed for the determination of 18 polychlorinated biphenyls (PCBs) in camellia seeds. The camellia seeds were extracted with acetonitrile, salted out with sodium chloride, then cleaned-up by QuEChERS with anhydrous MgSO4, C18, primary secondary amine (PSA), and multi walled carbon nanotubes (NANO) using multiple vortex after the centrifugal separation, and finally analyzed by GC-QQQ-MS/MS in multiple reaction monitoring mode via positive electrospray ionization. All the 18 PCBs could be completely separated with an excellent linear relationship. The limits of detection for the 18 PCBs were 5 μg/kg. For all the samples, the mean spiked recoveries was 109.2% with relative standard deviations (RSDs) of 2.9%-6.2% (n=3). The extraction, purification and analytical methods were developed and assessed. The method was successfully applied to the 48 samples from three main producing provinces of camellia seeds. All the 18 PCBs were not detected from the 48 samples.

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Determination of three organotin pesticide residues in apples and cabbages by gas chromatography-electron impact/positive chemical ionization mass spectrometry CAI Lisheng, SHEN Weijian, WANG Zhengping, ZHANG Rui, DING Tao, YU Keyao, WANG Hong, ZHANG Wenjun, GONG Yuxia 2017, 35 (11):  1177-1183.  DOI: 10.3724/SP.J.1123.2017.07011 Abstract ( 436 )   [Full Text(HTML)] () PDF (1032KB) ( 107 )   A method for the simultaneous determination of fenbutatin oxide, triphenyltin and cyhexatin in apples and cabbages was developed by gas chromatography-mass spectrometry coupled with two different ionization techniques, electron impact (EI) ionization and positive chemical ionization (PCI). At first, the samples were digested by hydrobromic acid, and extracted by acetone-hexane (1:2, v/v). The extracts were derivatized by sodium tetraethylborate as the derivatization reagent, and cleaned up by the Florisil SPE columns. Finally, the samples were analyzed by GC-EI/MS and GC-PCI/MS in selected ion monitoring (SIM) mode. The results showed that good linearities were obtained with correlation coefficients (r2) greater than 0.997 for fenbutatin oxide in the range of 75-500 μg/L in both foods, triphenyltin in the range of 50-1000 μg/L in cabbages and 50-500 μg/L in apples and cyhexatin in the range of 50-1000 μg/L in the two foods. The accuracy was checked at three spiked levels (50, 100 and 200 μg/kg) in cabbages and apples. The limits of detection (LODs, S/N=3) were 0.01-0.05 mg/kg (EI) and 0.01-0.02 mg/kg (PCI), and the limits of quantifications (LOQs, S/N=10) were 0.03-0.16 mg/kg (EI) and 0.02-0.06 mg/kg (PCI). The average recoveries ranged from 59.24%-97.36% (apples) and 50.54%-94.54% (cabbages) in the mode of EI, and the corresponding values were 65.38%-95.86% and 62.56%-90.44% in the mode of PCI. The relative standard deviations (RSDs) were all less than 6.9% (n=6). The PCI method can be used to improve the accuracy in comparing with the EI, in terms of good selectivity and high sensitivity.

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Determination of flavor compounds in foxtail millet wine by gas chromatography-mass spectrometry coupled with headspace solid phase microextraction LIU Jingke, ZHANG Aixia, LI Shaohui, ZHAO Wei, ZHANG Yuzong, XING Guosheng 2017, 35 (11):  1184-1191.  DOI: 10.3724/SP.J.1123.2017.07012 Abstract ( 564 )   [Full Text(HTML)] () PDF (3502KB) ( 219 )   To comprehensively understand flavor compounds and aroma characteristics of foxtail millet wine, extraction conditions were optimized with 85 μm polyacrylate (PA), 100 μm polydimethylsiloxane (PDMS), 75 μm carboxen (CAR)/PDMS and 50/30 μm divinylbenzene (DVB)/CAR/PDMS fibers. The flavor compounds in foxtail millet wine were investigated by gas chromatography-mass spectrometry (GC-MS) coupled with headspace solid phase microextraction (HS-SPME), and the odor characteristics and intensity were analyzed by odor active values (OAVs). The samples of 8 mL were placed in headspace vials with 1.5 g NaCl, then the headspace vials were heated at 60℃ for 40 min. Using HS-SPME with different fibers, a total of 55 flavor compounds were identified from the samples, including alcohols, esters, benzene derivatives, hydrocarbons, acids, aldehydes, ketones, terpenes, phenols and heterocycle compounds. The main flavor compounds were alcohols compounds. According to their OAVs, phenylethyl alcohol, styrene, 1-methyl-naphthalene, 2-methyl-naphthalene, benzaldehyde, benzeneacetaldehyde and 2-methoxy-phenol were established to be odor-active compounds. Phenylethyl alcohol and benzeneacetaldehyde were the most prominent odor-active compounds. PA and PDMS fibers had good extraction effect for polar and nonpolar compounds, respectively. CAR/PDMS and DVB/CAR/PDMS provided a similar compounds profile for moderate polar compounds. This research comprehensively determined flavor compounds of foxtail millet wine, and provided theoretical basis for product development and quality control.

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Isolation and purification of seven catechin compounds from fresh tea leaves by semi-preparative liquid chromatography GONG Zhihong, CHEN Si, GAO Jiangtao, LI Meihong, WANG Xiaxia, LIN Jun, YU Xiaomin 2017, 35 (11):  1192-1197.  DOI: 10.3724/SP.J.1123.2017.08002 Abstract ( 613 )   [Full Text(HTML)] () PDF (846KB) ( 311 )   An effective and simple method was established to simultaneously purify seven tea catechins (gallocatechin (GC), epigallocatechin (EGC), catechin (C), epigallocatechin-3-O-gallate (EGCG), epicatechin (EC), epigallocatechin-3-O-(3-O-methyl)-gallate (EGCG3"Me) and epicatechin-3-O-gallate (ECG)) from fresh tea leaves by semi-preparative high performance liquid chromatography (HPLC). Fresh leaves of Tieguanyin tea were successively extracted with methanol and chloroform. Then crude catechins were precipitated from the aqueous fraction of chloroform extraction by adding lead subacetate. Crude catechins were used for the isolation of the seven target catechin compounds by semi-preparative HPLC. Methanol-water and acetonitrile-water were sequentially used as mobile phases. After two rounds of semi-preparative HPLC, all target compounds were achieved with high purities (>90%). The proposed method was tested on two additional tea cultivars and showed similar results. This method demonstrated a simple and efficient strategy based on solvent extraction, ion precipitation and semi-preparative HPLC for the preparation of multiple catechins from tea leaves.

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Simultaneous determination of six fluorescent whitening agents in plastic and paper packaging materials by high performance liquid chromatography ZHANG Juzhou, JI Shuilin, CAI Huimei, LI Jing, WANG Yongxin, WANG Jingqiu 2017, 35 (11):  1198-1203.  DOI: 10.3724/SP.J.1123.2017.06024 Abstract ( 530 )   [Full Text(HTML)] () PDF (1629KB) ( 123 )   A novel analytical method was developed for the simultaneous determination of six fluorescent whitening agents (FWAs:FWA 135, FWA 184, FWA 185, FWA 199, FWA 378 and FWA 393) in paper and plastic food packaging materials by high performance liquid chromatography with fluorescence detection (HPLC-FLD). The sample was extracted with mixed solution of chloroform and acetonitrile (3:7, v/v), then cleaned up by HLB solid phase extraction column. Qualitative and quantitative analyses were carried out by HPLC. The sample was separated on a Phenomenex C18 column using acetonitrile and 5 mmol/L ammonium acetate aqueous solution as mobile phases. The results indicated that the linear range of FWA393 was 15-1500 μg/L and the linear ranges of the other five FWAs were 5-500 μg/L with correlation coefficients greater than 0.999. The recoveries in spiked samples were between 80.4% and 125.0% with RSDs (n=6) of 1%-13%. Furthermore, this method was applied to analyze 12 samples in the market to verify the practicality of the method. The method showed the advantages of simplicity, high recovery and good precision, and is suitable for the detection of the six fluorescent whitening agents in food packaging materials.

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Determination of oxygenates in methanol-to-olefin gasoline byproducts and methanol-to-gasoline product with solid phase extraction-gas chromatography TIAN Wenqing, LI Jiwen, WANG Chuan 2017, 35 (11):  1204-1209.  DOI: 10.3724/SP.J.1123.2017.07022 Abstract ( 421 )   [Full Text(HTML)] () PDF (793KB) ( 167 )   Silica solid phase extraction (SPE) column was used for sample pretreatment to enrich the target analytes and simplify background. Due to its high efficiency, reliability and simplicity, the technique has been widely used in many fields. The byproduct gasoline of methanol-to-olefin (MTO) and the product of methanol-to-gasoline (MTG) mainly consist of hydrocarbons along with small amounts of oxygenates. Trace amounts of oxygenates are hard to identify because of their complex hydrocarbon components. With the SPE technique, the samples were separated into two major classes, oxygenates and hydrocarbons. Oxygenates were then determined with gas chromatography-mass spectrometry (GC-MS). The elution conditions of the silica solid phase extraction column were optimized with the standard sample. Under the optimized elution conditions, the hydrocarbons were first eluted from the SPE column with 5 mL dichloromethane, the oxygenates were then eluted with 3 mL acetonitrile. The recoveries of standard samples were tested before and after pretreatment. The standard recoveries were 87.7%-95.3%. The oxygenates except methanol and ethanol were then quantified by gas chromatography-flame ionization detection (GC-FID) and internal standard method. Methanol and ethanol were then quantified by extracting characteristic ion chromatograms and external standard method. The results show that the oxygenates of MTO byproduct gasoline and MTG product mainly consist of ketones and aldehydes. The method improves the sensitivities of the target compounds and reduces the interference of the background.