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Chinese Journal of Chromatography
2018, Vol. 36, No. 1
Online: 08 January 2018

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Enantiomeric separation of D, L-isoleucine in citric acid-zinc (Ⅱ) medium by capillary electrophoresis CHEN Li, ZHENG Ying, CHEN Yufu, YUAN Qiuyue, XIE Tianyao 2018, 36 (1):  1-4.  DOI: 10.3724/SP.J.1123.2017.10008 Abstract ( 492 )   [Full Text(HTML)] () PDF (731KB) ( 131 )   The enantiomeric separation of unmodified D,L-isoleucine was achieved in citric acid-zinc(Ⅱ) medium by capillary electrophoresis (CE) with contactless conductivity detector (C4D). In the conventional chiral separation methods of amino acid, a chiral complex used as the chiral selector was added into the eluent in order to yield a chiral environment. However, in this study a non-chiral solution, i. e. 2.8 mmol/L NaOH+0.8 mmol/L citric acid+2.0 mmol/L zinc acetate was used as the running buffer, and the citric acid-zinc(Ⅱ) acted the role of a chiral selector. Under the optimum experimental conditions:uncoated fused-silica capillary (45 cm×50 μm, Leff=40 cm), separation voltage of +13 kV, electrokinetic injection of 11 kV×8 s, the enantiomers of D,L-isoleucine were baseline separated within 8 min with the resolutions (Rs) of 2.0. The calibration curve of each enantiomer showed good linearity in the range from 1.0 mg/L to 20 mg/L, with the limits of detection of 0.40 mg/L. The intra-and inter-day precisions were examined. The RSDs of peak area and migration time were found to be below 5.0% and 2.5% (n=6), respectively, indicating good repeatability (intra-day) and reproducibility (inter-day) of the method. Interference experiment was also tested. As a result, other common amino acids did not interfere with the detection. The proposed method provided a potential new way to further investigate the enantioseparation of unmodified or native amino acids.

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Preparation of monolithic fibers with deep eutectic solvent for solid phase microextraction of polycyclic aromatic hydrocarbons in lake water CHEN Na, ZHANG Yijun, ZHAO Wanli, CHEN Jun, ZHANG Yuping 2018, 36 (1):  5-11.  DOI: 10.3724/SP.J.1123.2017.10003 Abstract ( 605 )   [Full Text(HTML)] () PDF (4302KB) ( 174 )   A monolithic fiber of poly(butyl methacrylate-ethylene glycol dimethacrylate)[poly(BMA-EDMA)] was prepared using deep eutectic solvent (DES) of choline chloride-ethanediol as a porogen. The prepared fibers were applied to direct extraction of three polycyclic aromatic hydrocarbons (PAHs) in lake water samples by solid phase microextraction (SPME). The extracts were determined by ultra performance liquid chromatography (UPLC). The fiber without DES was prepared at the same time. Both fibers (with and without DES) were compared with a commercial polydimethylsiloxane (PDMS) fiber. The highest extraction efficiency was clearly obtained with poly(BMA-EDMA) fiber. The extraction time, extraction solvent, desorption time, desorption solvent, and ionic strength were optimized. Under the optimum conditions, the linear ranges for the three PAHs (naphthalene, biphenyl, and phenanthrene) were 0.1-6.0 mg/L (r ≥ 0.9903). The limits of detection (LODs) of the three PAHs were in the range of 2.1-4.9 μg/L. The recoveries of the three PAHs spiked in lake water samples were 86.4%-111.3% with relative standard deviations (RSDs, n=6) of 11.2%-15.1%. This method is simple, stable, and inexpensive, and can be used for the determination of the PAHs in lake water samples.

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Determination of 6-benzylaminopurine in edible mushrooms by solid liquid extraction with low-temperature partition and high performance liquid chromatography-mass spectrometry HOU Kun, WATANABE Masaki, WANG Dali, HAN Jing, LI Yonglu, HUO Hong 2018, 36 (1):  12-16.  DOI: 10.3724/SP.J.1123.2017.09028 Abstract ( 598 )   [Full Text(HTML)] () PDF (767KB) ( 91 )   A simple method based on solid liquid extraction with low-temperature partition (SLE-LTP) coupled with high performance liquid chromatography-mass spectrometry (HPLC-MS) was developed for the determination of 6-benzylaminopurine (6-BA) in edible mushrooms. The samples were extracted with acetonitrile followed by low-temperature partition at -30℃ for 4 h. The separation was performed on a Hitachi LaChrom C18 column (250 mm×4.6 mm, 5 μm) with 0.02 mol/L ammonium acetate (containing 0.1% (v/v) glacial acetic acid)-methanol (6:4, v/v) as the mobile phases with isocratic elution. The compound was detected in positive electrospray ionization mode, and quantified by external standard method. The results showed that the limit of detection (LOD, S/N>3) for the analyte was 0.006 mg/kg, and the limit of quantification (LOQ, S/N>10) was 0.02 mg/kg. The calibration curve showed good linear in the range of 0.05-2.0 mg/L, and the correlation coefficient (r2) was 1.0000. The spiked recoveries were between 81.3% and 93.7% with the relative standard deviations (RSDs, n=6) of 0.7%-2.4% at the spiked levels of 0.1 mg/kg and 0.5 mg/kg. The developed method is simple, reliable and can be applied for the accurate determination of 6-BA residue in edible mushrooms.

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Determination of myclobutanil and difenoconazole residues in pollen and honey of litchi by high performance liquid chromatography-tandem mass spectrometry WANG Siwei, LIU Yanping, SUN Haibin, DU Lanjuan, XU Nengli 2018, 36 (1):  17-22.  DOI: 10.3724/SP.J.1123.2017.09034 Abstract ( 620 )   [Full Text(HTML)] () PDF (935KB) ( 177 )   An effective method was developed for the determination of two major fungicides including myclobutanil and difenoconazole residues in pollen and honey of litchi by modified QuEChERS-high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The pollen and honey samples were all extracted by acetonitrile, the pollen samples were cleaned-up by 0.9 g anhydrous magnesium sulfate (MgSO4), 0.15 g primary secondary amine (PSA) and 0.15 g C18; the honey samples were cleaned-up by 0.9 g MgSO4 and 0.15 g PSA. The 0.1% (v/v) formic acid aqueous solution-acetonitrile (25:75, v/v) were used as the mobile phases. The extracts were separated on a Poroshell-120 EC-C18 chromatographic column, the positive electrospray ion (ESI+) source and selected ion monitoring (SIM) mode were used. The analytes were quantified by the matrix matching standard solutions. The matrix matched standard solutions of myclobutanil and difenoconazole showed good linearities in the range of 1-100 μg/L, and the correlation coefficients (r2) were all above 0.9990. The limits of detection (LODs) of myclobutanil and difenoconazole were 0.25 μg/kg and 0.50 μg/kg, respectively. The limits of quantification (LOQs) of myclobutanil and difenoconazole were 0.83 μg/kg and 1.7 μg/kg, respectively. The average recoveries of myclobutanil and difenoconazole in pollen and honey samples were 87.0%-95.2% and 90.1%-96.4% with the relative standard deviations of 1.2%-3.6% and 0.7%-4.1%, respectively. The method is quick, easy and sensitive, and it is suitable for the rapid determination and trace analysis of myclobutanil and difenoconazole in pollens and honeys of litchi. The method can provide data support for the exposure risk assessment of bees and other pollination insects.

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Analysis of the heterogeneity of Ralstonia solanacearum avirulent espD-mutant by high performance ion-exchange chromatography ZHENG Xuefang, CHEN Deju, CHEN Xiaoqiang, LIU Bo, ZHU Yujing 2018, 36 (1):  23-29.  DOI: 10.3724/SP.J.1123.2017.09024 Abstract ( 439 )   [Full Text(HTML)] () PDF (3339KB) ( 135 )   The heterogeneity of Ralstonia solanacearum avirulent espD-mutant, virulent wildtype strain FJAT-91 and spontaneous avirulent strain FJAT-1458 were compared and analyzed by using high performance ion-exchange chromatography (HPIEC). Their colony and cell morphologies were observed, and the contents of their extracellular polysaccharides (EPS) were determined. The results showed that the colony and cell morphologies of FJAT-91 ⊿epsD were different from the original strain FJAT-91, but were similar to the spontaneous avirulent strain FJAT-1458. The EPS content of FJAT-91 ⊿epsD was (12.64±1.46) μg/mL, which was much lower than FJAT-91 with (30.49±2.97) μg/mL. The strain FJAT-91 were separated into single peak of P3 at the retention time of 6.04 min, and FJAT-91 ⊿epsD had two peaks (P1 and P2) at the retention times of 0.59 min and 4.62 min, respectively. FJAT-1458 formed single peak of P1 at the retention time of 0.59 min. Then, the bacteria eluents from different chromatographic peaks were collected and their pathogenicities were detected with bioassay test using potted tomatoes in the greenhouse. The results showed that the tomato plants began to wilt 4 d after inoculation of strain FJAT-91-P3 eluted from P3, and the disease incidence reached 100% at 10 d post inoculation. The strain FJAT-91 ⊿epsD-P2 eluted from P2 caused tomato plants wilting 9 d after inoculation, and the disease incidence reached 100% at 20 d. During 20 d of observation, none of tomato plants caused wilting while inoculation with FJAT-1458-P1 and FJAT-91 ⊿epsD-P1 eluted from P1 of FJAT-1458 and FJAT-91 ⊿epsD, respectively. In this paper, the morphologies, EPS contents and chromatographic behaviors of FJAT-91, FJAT-91 ⊿epsD and FJAT-1458 were compared, which would provide theoretical basis for using FJAT-91 ⊿epsD to control bacterial wilt disease.

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Determination of organophosphorus and carbamate insecticide residues in food and water samples by solid phase extraction coupled with capillary liquid chromatography LIU Jie, LU Wenhui, CUI Rong, SUN Xiyan, LI Jinhua, CHEN Lingxin 2018, 36 (1):  30-36.  DOI: 10.3724/SP.J.1123.2017.09023 Abstract ( 503 )   [Full Text(HTML)] () PDF (1945KB) ( 122 )   A method was established for the simultaneous separation and determination of one organophosphorus and three carbamate insecticide residues in food and water samples by solid phase extraction (SPE) followed by analysis using a home-made capillary liquid chromatogram. Various parameters possibly affecting the efficiencies of capillary liquid chromatography (CLC) and SPE were investigated in detail, such as type of SPE column, pH value of samples, type and volume of elution solvent, flow rate of loading sample, salt effect, loading volume, detection wavelength, and type and ratio of mobile phases. Under the optimized experimental conditions, the four insecticides were separated completely within 6 min. The limits of detection and limits of quantification were 0.35-1.20 μg/kg and 1.17-4.00 μg/kg, respectively. Satisfactory recoveries of the SPE-CLC method were achieved for spiked food samples of tomato, cucumber and apple ranging from 72.41% to 107.15% with the relative standard deviations (RSDs) no more than 8.12%, and for spiked tap/lake water samples ranging from 71.45% to 109.25% with the RSDs no more than 9.28%. The method can meet the requirements for multi-residue analysis of insecticides.

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Separation of chemical compositions in root of Rumex patientia L. with off-line two-dimensional liquid chromatography ZHAO Yaqing, FU Dongmei, LIU Yanfang, LIANG Xinmiao, XUE Huiqing 2018, 36 (1):  37-42.  DOI: 10.3724/SP.J.1123.2017.09021 Abstract ( 524 )   [Full Text(HTML)] () PDF (983KB) ( 108 )   An innovative analytical method based on the off-line two-dimensional reversed-phase/reversed-phase liquid chromatography (2D-RPLC/RPLC) was established to separate the components of root of Rumex patientia L. The chromatograms of ethyl acetate extract of root of Rumex patientia L. on a phenyl/tetrazolium column (250 mm×4.6 mm, 7 μm) and a Unitary C18 column (250 mm×4.6 mm, 7 μm) were compared, and they showed different separation abilities. A phenyl/tetrazolium column was used for the first dimensional separation with 0.1% (v/v) formic acid aqueous solution and methanol as mobile phases, and 18 fractions was collected. The second dimensional liquid chromatography analysis was carried out on a Unitary C18 column with 0.1% (v/v) formic acid aqueous solution and methanol as mobile phases. Based on the experiment setup and results, it was concluded that off-line 2D-LC can be an effective method for the separation of the trace components and the screening of active compounds of root of Rumex patientia L.

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Determination of fatty acids in natural cream and artificial cream by comprehensive two-dimensional gas chromatography-mass spectrometry ZHOU Ruize, ZHOU Ya, MAO Ting, JIANG Jie 2018, 36 (1):  43-50.  DOI: 10.3724/SP.J.1123.2017.09027 Abstract ( 716 )   [Full Text(HTML)] () PDF (2512KB) ( 260 )   A method for the determination of 37 fatty acids in natural cream and artificial cream was developed by comprehensive two-dimensional gas chromatography-mass spectrometry (GC×GC-MS). The samples were extracted with toluene and acetyl chloride-methanol (1:9,v/v) solution was added to the extract for fat esterification. Finally, the fatty acids were analyzed by GC×GC-MS. The GC conditions were as follows:a DB-5 column (30 m×0.25 mm×0.25 μm) was set as the 1st dimensional column and a BPX-50 column (2.5 m×0.1 mm×0.25 μm) was the 2nd dimensional column. The primary oven temperature was programmed from 50℃ (held for 2 min) to 180℃ at a rate of 20℃/min, followed by an increase to 250℃ at 2.5℃/min, then raised up to 300℃ (held for 5 min) at 3℃/min. The ion source temperature was 200℃ with auxiliary temperature of 300℃ in scan mode. All fatty acids were separated effectively and determined accurately while the modulation period was 5s and the scan range of MS was m/z 40-385. This procedure was applied to analyze the fatty acids in commercial natural cream and artificial cream from Chinese markets, among which we found the characteristic components in different kinds of samples. Compared with gas chromatography-flame ionization detector (GC-FID), GC×GC-MS method was more sensitive and more components of fatty acids were detected. Conclusively, this work suggests a new technical approach in analyzing fatty acids in natural cream and artificial cream, which is meaningful to ensure the quality identification and safety of natural cream.

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Determination of 16 polycyclic aromatic hydrocarbons in marine sediments by gas chromatography-tandem mass spectrometry with accelerated solvent extraction SONG Xiaojuan, LI Haiyan, YIN Mingming, MA Yuqin 2018, 36 (1):  51-58.  DOI: 10.3724/SP.J.1123.2017.09044 Abstract ( 578 )   [Full Text(HTML)] () PDF (1852KB) ( 198 )   A method based on gas chromatography-tandem mass spectrometry (GC-MS/MS) with accelerated solvent extraction (ASE) was developed for the determination of 16 polycyclic aromatic hydrocarbons (PAHs) in marine sediments. The sediment samples were extracted with hexane-acetone (1:1, v/v). The extracts were dehydrated with anhydrous sodium sulfate, and concentrated with a termovap sample concentrator. The concentrated solutions were further cleaned up with Si SPE columns. The purified solutions were then isolated by HP-5MS column (30 m×0.25 mm×0.25 μm). The analytes were detected using electron impact source under multiple reaction monitoring (MRM) mode. The results showed that the 16 PAHs had good linearities in the range of 0.01-1.00 mg/L with the correlation coefficients (R) greater than 0.997. The spiked recoveries of the 16 PAHs were in the range of 75.8%-97.8%, and the relative standard deviations (RSDs) were less than 10%. The method detection limits (MDLs) of the 16 PAHs ranged from 0.048-0.234 μg/kg with 20.0 g sampling weight. This method is suitable for the determination of trace PAHs in marine sediments.

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Rapid resolving algorithm of gas chromatographic overlapping peaks based on the asymptotic expansion of integration KE Qing, GAO Qingwei, LU Yixiang 2018, 36 (1):  59-68.  DOI: 10.3724/SP.J.1123.2017.09018 Abstract ( 515 )   [Full Text(HTML)] () PDF (2052KB) ( 86 )   A novel algorithm, called asymptotic expansion of integration, is suggested to resolve gas chromatographic overlapping peaks. There are three steps for the algorithm. First, a valley peak or a shoulder peak is separated into two domains, and an integral equation on a subdivision and an algebraic equation on the overlapping peak domain are listed. Secondly, areas needed in two equations, are computed by a numerical integral method, then the integral equation is expended to an algebraic equation by the asymptotic formula of integration. At last, combing two equations with constraint equations of peak heights, we got a nonlinear algebraic set. The equation set can be solved rapidly by Gauss-Seidel iteration, and the maximum number of iterations is not more than 20 times. The simulation and experimental results showed that height and area errors of resolving peaks are quite small, the maximum error of area is less than 6.44%, and that of the height is about 6.80%. Because of the high accuracy and computational efficiency, the algorithm can be used in decomposition of gas chromatographic overlapping peaks and online real-time processing of general chromatographic overlapping peaks.

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Investigation on the interaction between pentadecafluorooctanoic acid and human serum albumin by capillary electrophoresis GU Yi, GUO Ming, LÜ Da, HOU Ping, YIN Xinxin 2018, 36 (1):  69-77.  DOI: 10.3724/SP.J.1123.2017.09041 Abstract ( 444 )   [Full Text(HTML)] () PDF (856KB) ( 117 )   Capillary electrophoresis (CE) has been used to establish the analytical method of interaction between pentadecafluorooctanoic acid (PFOA) and human serum albumin (HSA). Under the physiological conditions, the interaction model of PFOA and HSA were constructed. Mobility method, plug-plug kinetic (PPK) method and simplified Hummel-Dreyer method were used to determine the interaction between derivatives and HSA. Non-linear regression, Scatchard equation and Klotz equation were adopted to obtain the interaction parameters. The results showed that all the three methods can be used to analyze the interaction of PFOA-HSA system. According to the interaction parameters, the most suitable CE method is simplified Hummel-Dreyer method while the most suitable theoretical equation is non-linear regression. The binding parameters indicated that the interaction of PFOA-HSA system has only one type of binding sites and the binding is stable. The research results have illustrated the interaction between HSA and PFOA, and provided a beneficial reference for in-depth research of the toxic mechanism of PFOA.

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Determination of cyanamide residue in grapes and cherries by liquid chromatography-tandem mass spectrometry coupled with precolumn derivatization LAN Feng, LIU Chuande 2018, 36 (1):  78-82.  DOI: 10.3724/SP.J.1123.2017.09004 Abstract ( 692 )   [Full Text(HTML)] () PDF (755KB) ( 213 )   A method was developed for the quantitative determination of cyanamide in grapes and cherries by liquid chromatography-tandem mass spectrometry (LC-MS/MS) coupled with dansyl chloride (DNS) precolumn derivatization. First, the samples were homogenized, and then extracted with ethyl acetate under ultrasonication. The water was removed using anhydrous sodium sulfate, and the extract was concentrated and derivatized with dansyl chloride under alkaline condition. The separation was performed on a Shimadzu Shim-pack XR-ODS column (75 mm×2.0 mm, 1.6 μm) with the mobile phases of methanol and 2 mmol/L ammonium acetate aqueous solution (containing 0.05% (v/v) formic acid) in a gradient elution mode. The identification and quantification of cyanamide were carried out by MS/MS in positive electrospray ionization (ESI+) and multiple reaction monitoring (MRM) mode. The calibration curves showed good linearities in the range of 0.01-1.0 mg/L with the correlation coefficients not less than 0.9990. The average recoveries of cyanamide spiked at 0.01, 0.05 and 1.0 mg/kg in cherries and grapes were between 75% and 81%, and the relative standard deviations (RSDs) were between 6.5% and 9.8%. Both the limits of quantification (LOQs) of the analytes were 0.01 mg/kg. The method is simple, rapid, accurate and suitable for the confirmation and quantification of cyanamide in cherries and grapes.