Chinese Journal of Chromatography

2012 annual review of capillary electrophoresis technology

QU Feng1*, ZHAO Xinying1,2, WANG Yong1

2012, 30 (12): 1214-1219. DOI: 10.3724/SP.J.1123.2012.12001

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This paper reviews the capillary electrophoresis (CE) in 2012. Four international and three national conferences are included and the important reports are introduced briefly. Literatures searched from ISI Web of Science ranged in 2012.1.1~2012.12.1 are classified and introduced based on the biology and medicine applications as well as the use of detectors and the important analytical chemical journals.

Development of molecularly imprinted microextraction techniques

ZHANG Kaige, HU Yuling, HU Yufei, LI Gongke*

2012, 30 (12): 1220-1228. DOI: 10.3724/SP.J.1123.2012.08002

Abstract ( 1746 ) [Full Text(HTML)] ()

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Microextraction techniques can extract efficiently the analytes from a sample matrix to the polymers or organic solvents of microvolume, and integrate sampling, extraction, concentration and injection into one single step. They have the advantages of simple, time-efficient and solvent-free. They have been successfully coupled with a variety of analytical tools, such as gas chromatography and high performance liquid chromatography. Molecularly imprinted polymers have specific recognition ability. They can separate and enrich analytes from complicated matrix with high selectivity, and they have great application prospects in complicated sample preparation. This review summarizes the progress in the molecularly imprinted microextraction techniques, including molecularly imprinted-solid phase microextraction, molecularly imprinted-stir bar adsorptive extraction, magnetic molecularly imprinted beads extraction, etc. A total of 75 references are cited.

Comparison of interaction between cytochrome c and single strain deoxyribonucleic acid pools based on capillary electrophoresis

MEI Fang1, ZHAO Xinying1,2, QU Feng1*

2012, 30 (12): 1229-1234. DOI: 10.3724/SP.J.1123.2012.09033

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An assessment method of the interaction between cytochrome c (Cyt c) selected as a representative basic protein and three lengths of single strain deoxyribonucleic acid (ssDNA) pools was presented based on capillary electrophoresis. The investigation of ionic strength effect on the interaction was made. The interactions between Cyt c and the ssDNA pools with 20 nt, 40 nt and 60 nt random sequences were compared by capillary zone electrophoresis (CZE) based on an uncoated fused capillary and a coated capillary. Using the uncoated fused capillary, the interaction difference could not be observed due to the strong adsorption of Cyt c on the inner surface of the capillary. However, under negative potential with the assistance of pressure driving, the peak area change of free ssDNA indicated the interaction difference of the three pools with Cyt c using the coated capillary, and the results showed that the ssDNA pool with 20 nt random sequence exhibited the strongest interaction. In addition, NaCl concentration had great effect on the interaction of Cyt c with ssDNA60, and 0.02 mol/L NaCl solution was favored. For the selection of basic target proteins, the adjustment of salt concentration would inhibit the non-specific electrostatic interaction, improve the selection efficiency of a selection round. The favorable salt concentration could be optimized with an uncoated fused capillary by comparing the peak area change of the complex and free ssDNA pool.

Determination of the migration of seven photoinitiators in food packaging materials into aqueous solvent

LIU Pengyan*, HUANG Enjie, CHEN Yanjie

2012, 30 (12): 1235-1240. DOI: 10.3724/SP.J.1123.2012.09001

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The quantity of photoinitiators (PIs) migrated into hydrosoluble foods from packaging materials is usually very small. It is hardly detectable by using the current methods. For this reason, the article describes a new effective method for detecting the migration of PIs. In this method, the migration experiment was done in aqueous food simulation. After the PIs in printing inks used in food contact materials were extracted from the solution via solid-phase microextraction (SPME) using 65 μm polydimethylsiloxane/divinylbenzene (PDMS-DVB)-coated fiber, their migration amounts were determined by gas chromatography-mass spectrometry (GC-MS) in the selected ion monitoring mode (SIM). The PIs determined by SPME/GC-MS were benzophenone (BP), 1-hydroxycyclohexyl-phenylketone (CPK), ethyl-4-dimethyl-aminobenzoate (EDMAB), 4-methylbenzophenone (4-MBP), 2,2-dimethoxy-2-phenylacetophenone (2,2-DMPA), methyl 2-benzoylbenzoate (OMBB) and 2-ethylhexyl-4-dimethyl-aminobenzoate (EHDAB). The limits of detection (S/N=3) were between 0.0012 and 0.0069 μg/L. The linearity ranged from 0.03 to 1.0 μg/L (r2＞0.9909). The recoveries were in the range from 70.8% to 112.0% (n=3) with the relative standard deviations no more than 14.0%. Twenty samples were tested by using this developed method. The analytical results showed that BP was detected in all samples, and the migration amounts of BP were from 0.002 to 0.074 μg/dm2; 4-MBP was detected in ten samples, and the migration amounts of 4-MBP were from 0.006 to 0.019 μg/dm2; CPK was detected in three samples, and its amounts were 0.005, 0.005, 0.007 μg/dm2; 2,2-DMPA was detected as 0.009 μg/dm2 in one sample. The determination of real samples showed this method is feasible. The method is sensitive, simple and free from organic solvents. It could make reference to migrating determination of PIs in printing inks on food packaging surface.

Determination of polybrominated diphenyl ethers in indoor dust using ultrasonic-assisted extraction and gas chromatography-negative chemical ionization mass spectrometry

ZHANG Xiaoling1, WANG Bingling2*, LU Xiaomei1, ZHANG Qi2, ZHANG Zhengdong2

2012, 30 (12): 1241-1245. DOI: 10.3724/SP.J.1123.2012.08020

Abstract ( 1448 ) [Full Text(HTML)] ()

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A method for the determination of eight polybrominated diphenyl ethers (PBDEs) in indoor dust was developed. A vacuum cleaner was used for gathering the house dust, and n-hexane was added and the extraction was performed in an ultrasonic bath. The supernatant was concentrated and then n-hexane was added to 0.1 mL. Gas chromatography-negative chemical ionization mass spectrometry (GC-NCI/MS) has been investigated for the determination of the eight PBDE congeners in indoor dust. The eight PBDEs were separated within 20 min. The absolute recoveries were 53.2%~107.6%. The relative standard deviations (RSDs) of intra-day were between 2.8% and 16.5%, while the RSDs of inter-day were between 6.4% and 22.6%. The limits of detection (LOD, S/N=3) were in the range of 0.003~0.015 ng/g except the LOD of BDE-209 was 0.15 ng/g. The results indicated that the proposed method is sensitive, accurate, fast, simple, low solvent consumption and suitable for the determination of tri- to deca-BDEs in indoor dust.

Fast screening ninety-six pesticides in six kinds of agricultural products by high performance liquid chromatography-quadrupole/electrostatic field orbit trap high-resolution mass spectrometry

WU Bin, DING Tao*, LIU Han, CHEN Huilan, ZHAO Zengyun, ZHANG Rui, SHEN Chongyu

2012, 30 (12): 1246-1252. DOI: 10.3724/SP.J.1123.2012.07014

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A high-throughput method for the determination of 96 pesticides in six kinds of agricultural products by liquid chromatography-quadrupole/electrostatic field orbit trap high-resolution mass spectrometry was developed. After extraction with 0.1% acetic acid in acetonitrile solution and concentration, dispersive solid-phase extraction was further utilized to reduce the matrix interference. The chromatographic analysis was performed on a C18 column with methanol and 5 mmol/L ammonium acetate solution as the mobile phases with a gradient elution program. The 96 pesticide residues were analyzed in switching positive and negative modes at the same time. With the optimized mass resolution, accurate mass-to-charge ratio extraction of the target pesticide compounds in full scan mode could eliminate matrix interference effectively. Two-stage threshold-triggered full mass scan mode was utilized to further improve the accuracy of qualitative analysis. The linear ranges of all the 96 pesticides were from 1 μg/L to 200 μg/L with correlation coefficients greater than 0.99. By detecting spiked samples, the detection limits were 5 μg/kg for all the residues and the recoveries were in the range of 58%~105% with the relative standard deviations (RSDs) between 8.8% and 18.3%.

Multi-residue determination of five antiviral drugs in chicken tissues by liquid chromatography-electrospray ionization tandem mass spectrometry

LIU Zhengcai*, YANG Fang, YU Kongjie, LIN Yonghui, LIU Suzhen, ZHANG Qiong, SU Zhijiao

2012, 30 (12): 1253-1259. DOI: 10.3724/SP.J.1123.2012.07038

Abstract ( 1648 ) [Full Text(HTML)] ()

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A method of liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) for the simultaneous determination of five antiviral drug residues, amantadine, rimantadine, memantine, moroxydine and imiquimod in chicken tissues was developed. The compounds were extracted from the samples with trichloroacetic acid solution and acetonitrile, and then cleaned-up by strong cation exchange (SCX) solid phase extraction cartridges. The analytes were separated on a Xamide column (100 mm×2.1 mm, 5 μm) and determined qualitatively and quantitatively with tandem mass spectrometry using positive polarity mode under multi-reaction monitoring (MRM) scan type. The limits of detection and the limits of quantification were 0.06~0.30 μg/kg and 0.2~1.0 μg/kg, respectively. The average recoveries of the five drugs were 72.3%~94.2% in chicken muscle and 70.8%~92.7% in chicken livers. The relative standard deviations (RSDs) in chicken muscle and livers were 3.5%~11.3% and 5.3%~12.6%, respectively. The method is selective without interference and suitable for the determination and confirmation of the five antiviral drugs in chicken muscle and livers.

Determination of glufosinate residue in tea by liquid chromatography-tandem mass spectrometry coupled with precolumn derivatization

LIN Yonghui*, LIU Zhengcai, YANG Fang, QIU Yuanjin, LIU Suzhen, SU Zhijiao, ZHANG Qiong, XUE Zhimin, FANG Yu

2012, 30 (12): 1260-1264. DOI: 10.3724/SP.J.1123.2012.07031

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A liquid chromatography-tandem mass spectrometry （LC-MS/MS） method was established for the determination of glufosinate (GLUF) residue in tea. The GLUF was extracted with water for 30 min under ultrasonication, and cleaned-up using a C18 solid phase extraction cartridge, then derived using fluorenylmethylchloroformate (FMOC-Cl) in borate buffer for 2 h. The separation was performed on a Kinetex C18 column with the mobile phases of acetonitrile and 5 mmol/L ammonium acetate aqueous solution (containing 0.2% (v/v) formic acid) in a gradient elution mode. The identification and quantification of the GLUF were carried out by MS/MS in negative electrospray ionization (ESI~) and multiple reaction monitoring (MRM) mode, the quantification analysis was performed by external standard method. The calibration curve showed good linearity in the range of 2.5~50.0 μg/L with the correlation coefficient r2＞0.999. The limit of quantification (LOQ) was 0.10 mg/kg. The average recoveries of GLUF spiked at 0.10, 0.50 and 1.00 mg/kg levels in tea were between 61.6% and 81.4%, and the relative standard deviations (RSDs) were between 3.2% and 8.4%. The method is simple, rapid, sensitive, accurate and suitable for the confirmation and quantification of GLUF in tea.

Chiral separation of benzamide antipsychotics and determination of their enantiomers by high performance liquid chromatography

WANG Liping, FAN Huajun*, WU Kunhong, PENG Xiaosheng, JIANG Zitao, ZANG Linquan

2012, 30 (12): 1265-1270. DOI: 10.3724/SP.J.1123.2012.07035

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A new method of the chiral separation of three drugs such as sulpiride, amisulpride and mosapride was developed on the chiral stationary phase of amylose-tris-(5-chloro-2-methyl- phenylcarbamate) (ACMPC) by high performance liquid chromatography. The chromatographic behaviors of enantiomers of the three drugs were investigated in the mobile phases consisted of ethanol and n-hexane （containing 0.1%(v/v) diethylamine）. The chromatographic conditions including the composition of the mobile phase, additives and temperature were further optimized for the chiral separation. The mechanism of racemic resolution for the mentioned drugs is discussed thermodynamically and structurally. The results indicated that these three chiral drugs could be separated on an ACMPC column under the optimum conditions, and their chiral resolutions were improved up to more than 1.5. The chromatographic parameters such as the retention factor k, separation factor α are presented, and the thermodynamic functions were calculated for the separation of the enantiomers of the three drugs. The method has been successfully applied to the determination of the enantiomers of the three drugs in tablets and blood serum. It is simple, reliable and accurate.

Effects of different processing methods on five main chemical constituents of Anemarrhena asphodeloides Bge. studied by high performance liquid chromatography

ZHAO Lulu1, LIU Feifei1, PENG Ying1,2*, KANG Tingguo2

2012, 30 (12): 1271-1275. DOI: 10.3724/SP.J.1123.2012.07024

Abstract ( 1448 ) [Full Text(HTML)] ()

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A high performance liquid chromatographic (HPLC) method has been developed for the simultaneous determination of neomangiferin, mangiferin, timosaponin BIII, anemarrhenasaponin I and timosaponin AIII in the products of Anemarrhena asphodeloides Bge. processed by different methods. By comparing and analyzing the variation of the contents of the five components, the effects of processing on chemical constituents of Anemarrhena asphodeloides Bge. were explored, which provided evidences for the relevance between processing and the property changes of Anemarrhena asphodeloides Bge. The chromatographic separation was performed on an AlltimaTM C18 column (250 mm×4.6 mm, 5 μm) with a gradient elution of acetonitrile (A) and 0.1% formic acid (B) (0~10 min, 5%A~20%A; 10~15 min, 20%A~25%A; 15~30 min, 25%A~80%A; 30~35 min, 80%A~100%A) at a flow rate of 0.8 mL/min. Neomangiferin and mangiferin were detected by an ultraviolet detector at 265 nm and room temperature. Timosaponin BIII, anemarrhenasaponin I and timosaponin AIII were detected by an evaporative light scattering detector with the drift temperature at 50 ℃ and gas pressure at 179.1 kPa (26 psi). To some extent, the contents of the major components varied in different processed products of Anemarrhena asphodeloides Bge. The results indicated that different processing methods caused significant differences in the contents of the major components of Anemarrhena asphodeloides Bge. It is of great use for further researching the relevance of the processing methods to pharmacodynamics of Anemarrhena asphodeloides Bge.

Simultaneous determination of five alkaloids in Niuhuang Shangqing Tablets by micellar electrokinetic chromatography-mass spectrometry using laurel acyl malic acid ester

HU Mengdi1,2, SU Di1,2, FAN Xiaosu1,2, YU Jianhua2, XU Yuanjin1,2*

2012, 30 (12): 1276-1281. DOI: 10.3724/SP.J.1123.2012.09044

Abstract ( 1340 ) [Full Text(HTML)] ()

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A micellar electrokinetic chromatography-mass spectrometric method based on laurel acyl malic acid ester (LMAE) for the separation and determination of coptisine, berberine, jatrorrhizine, phellodendrine and ligustrazine in Niuhuang Shangqing Tablets was established. The baseline separation of the five compounds was attained within 18 min by an uncoated capillary (88 cm×50 μm) on the operating voltage of 25 kV using 7.5 mmol/L LMAE-15 mmol/L ammonia-50 mmol/L ammonium acetate mixture (pH=7.0) containing 12.5% (v/v) acetonitrile as the electrophoretic medium and 50% 2-propanol aqueous solution (containing 3 mmol/L acetic acid) as the sheath liquid. The peak area of each component to its concentration showed a good linear relationship. The relative standard deviations of migration times and peak areas of the five components were less than 5% and the recoveries were between 96.0% and 105%. The developed method is simple, rapid, accurate and is suitable for the routine analysis of the five alkaloid components in Niuhuang Shangqing Tablets.

Determination of six anthraquinone compounds in soil by parallel type dual gradient high performance liquid chromatography

MA Hao, HE Wei, YANG Liu, YIN Xuemei, WANG Wenjia, SHI Chaoou*

2012, 30 (12): 1282-1286. DOI: 10.3724/SP.J.1123.2012.07037

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A high performance liquid chromatography (HPLC) was established for the determination of six anthraquinone compounds, 1,8-dinitroanthraquinone, 1,5-dinitroanthraquinone, 1-aminoanthraquinone, anthraquinone, naphthalene, 1,4,5,8-tetrachlorodibenzo anthraquinone, in polluted soil of residential construction. In this method, by using an Ultimate dual gradient liquid chromatograph (DGLC), designing a set of parallel dual system and accepting two same Dikma Diamonsil C18 columns (150 mm×4.6 mm, 5 μm) to cross-analysis, 41.46% of the analysis time can be saved. By using assisted ultrasonication to the extraction of the six substances in the samples with 50 mL N,N-dimethyl-formamide/1,4-dioxane/methanol (5/20/25, v/v/v), the average recoveries of the six analytes spiked in nine blank soil samples were 82.7%~101% with the relative standard deviations (RSDs) of 1.8%~3.2% and the limits of detection were 0.007~0.054 mg/kg, which can reach the limited requirement of the local standard in Beijing of DB11/T 811-2011. With the advantages of accessibility, high sensitivity and good reproducibility, this method can be used in the determination of anthraquinone compounds in soil.

Determination of free formaldehyde in cosmetics by pre-column derivatization, extraction inhibition and high performance liquid chromatography

Lv Chunhua1*, HUANG Chaoqun1, CHEN Mei2, XIE Wen1, CHEN Xiaomei1

2012, 30 (12): 1287-1291. DOI: 10.3724/SP.J.1123.2012.04042

Abstract ( 2182 ) [Full Text(HTML)] ()

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Pre-column derivatization and inhibition by solvent extraction were applied to determine free formaldehyde in cosmetics by high performance liquid chromatography (HPLC). Due to the rapid decomposition of formaldehyde donors in the derivatization, it is hard to detect the amount of the free formaldehyde in cosmetics. The formaldehyde directly reacted with 2,4-dinitrophenylhydrazine in acetonitrile-phosphate buffer (pH 2) (1:1, v/v) solution for 2 min, then dichloromethane extraction was used to induce the decomposition of formaldehyde donors. The extract was diluted with acetonitrile and then determined by HPLC. The formaldehyde derivative was separated on an Agilent C18 column (250 mm×4.6 mm, 5 μm) at 30 ℃ with acetonitrile-water (60:40, v/v) as mobile phase at a flow rate of 1.0 mL/min, and detected at the wavelength of 355 nm. The recoveries were from 81% to 106% at the spiked levels of 50, 100, 500, 1000 μg/g of formaldehyde in shampoo, milk, cream, hand cleaner, toothpaste, nail polish, powder separately, and the relative standard deviations (n=6) were less than 5.0%. The limit of quantification of the formaldehyde in cosmetics was 50 μg/g. The method has been applied to the determination of free formaldehyde in real samples and the results showed that the release by formaldehyde donors was inhibited. The method has the advantages of simple operation, good accuracy and meets the requirement of determination of free formaldehyde in cosmetics.

Determination of a major constituent in deoxyspergualin drug by reversed-phase ion-pair chromatography

CHENG Xiaokun, WANG Yali, ZHANG Huimin, NIU Changqun*

2012, 30 (12): 1292-1294. DOI: 10.3724/SP.J.1123.2012.08044

Abstract ( 1472 ) [Full Text(HTML)] ()

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A method was established for the determination of deoxyspergualin using reversed-phase ion-pair chromatography (RP-IPC). Several parameters, such as the chromatographic column, the types and concentration of ion-pair reagents, the concentration of the buffer and the pH value of the mobile phase were evaluated. The optimal separation conditions were as follows: C18 column (250 mm×4.6 mm, 5 μm); mobile phase, 5 mmol/L di-potassium hydrogen phosphate (containing 5 mmol/L 1-pentanesulfonic acid sodium, pH 3.6±0.3)-acetonitrile (90:10, v/v); flow rate, 1.0 mL/min; detection wavelength, 210 nm; column temperature, 30 ℃; injection volume, 20 μL. Under the optimaized experimental conditions, good linear relationships was obtained and the limit of detection for deoxyspergualin was 0.5mg/L.

Capillary electrophoresis analysis for glyphosate, glufosinate and aminomethylphosphonic acid with laser-induced fluorescence detection

CAO Liwei*, LIANG Siliu, TAN Xiaofang, MENG Jianxin

2012, 30 (12): 1295-1300. DOI: 10.3724/SP.J.1123.2012.09007

Abstract ( 1627 ) [Full Text(HTML)] ()

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A sensitive analytical method was developed for the simultaneous determination of glyphosate, glufosinate and aminomethylphosphonic acid by capillary electrophoresis with laser-induced fluorescence detection (CE-LIF). 5-(4,6-Dichlorotriazinyl) amino fluorescein (DTAF) was successfully applied to label the herbicides. The optimal derivatization reaction was carried out in boric acid buffer of pH 9.5 at 30 ℃ for 40 min. The baseline separation of the three derivatives could be accomplished using 30 mmol/L boric acid, 15 mmol/L Brij-35 (pH 9.5) as the running buffer. The detection limits (S/N=3) for the glyphosate, glufosinate and aminomethylphosphonic acid were 3.21, 6.14, 1.99 ng/kg, respectively. Finally, the method was successfully applied to the analysis of environmental samples, and the three compounds were measured without any interference from real samples. The recoveries of the compounds in these samples were 91.3%~106.0%. The method has the advantages of easiness and sensitivity, and can meet the requirement of the determination of the herbicide and metabolite residues in the environmental samples.

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