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Chinese Journal of Chromatography
2010, Vol. 28, No. 3
Online: 28 March 2010

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Development of two-dimensional micro strong cation exchange liquid chromatography/reversed phase pressurized capillary electrochromatography and its application on Cortex Phellodendri extract WU Yi, WANG Yan, GU Xue, ZHANG Lin, YAN Chao 2010, 28 (3):  226-230.  DOI: 10.3724/SP.J.1123.2010.00226 Abstract ( 2638 )   [Full Text(HTML)] () PDF (256KB) ( 736 )   Pressurized capillary electrochromatography (pCEC) combines capillary electrophoresis (CE) with high performance liquid chromatography (HPLC), resulting in high separation efficiency, high selectivity, high resolution and fast speed. In addition, it provides a solvent gradient capability. Based on pCEC, a two-dimensional chromatography was constructed using micro strong cation exchange liquid chromatography and reversed phase pressurized capillary electrochromatography (μ-SCXLC/RP-pCEC) for the analysis of Cortex Phellodendri extract. A sample was separated by the first dimensional SCX column with a linear salt gradient elution into 11 plugs. Each plug was collected and injected into the second dimensional RP-pCEC column with a linear gradient for further separation. Compared with one-dimensional liquid chromatography, it has higher resolution and larger peak capacity. The two-dimensional chromatographic system is suitable for the separation and analysis of complex samples.

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Preparation of hydrophilic interaction monolithic column and its application in the analysis of melamine in dairy products using pressurized capillary electrochromatography LI Xinyan, WANG Yan, GU Xue, CHEN Yan, YAN Chao 2010, 28 (3):  231-235.  DOI: 10.3724/SP.J.1123.2010.00231 Abstract ( 2709 )   [Full Text(HTML)] () PDF (297KB) ( 646 )   The hydrophilic monolithic column was prepared in 100 μm i.d. capillary in situ using ethylene dimethacrylate as crosslinker, butyl methacrylate and 3-［dimethyl-［2-(2-methylprop-2-enoyloxy)ethyl］azaniumyl］propane-1-sulfonate as monomers. In the study, the hydrophilic interaction behavior of the monolithic column was demonstrated. The application of the column in pressurized capillary electrochromatography (pCEC) for the separation of melamine with ultraviolet detection has been studied. The effects of the composition of mobile phase, pH value, the concentration of the buffer, the flow rate of pump and voltage were investigated. The optimum separation for melamine was achieved with the mobile phase of 10 mmol/L phosphate buffer (pH 3.0) and acetonitrile (20:80, v/v), voltage at 3 kV and UV detection at 215 nm. The limits of detection (LODs) (S/N=3) for melamine standard was 0.05 mg/L. The method is simple, accurate and works well without using the ion-pairing agent. The powdered milk and liquid milk were analyzed quantitatively by pCEC using the hydrophilic interaction monolithic column. It is shown that this method is promising in the routine analysis of melamine in dairy products.

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Preparation of monolithic polylaurylmethacrylate column and its application in capillary electrochromatographic separation of myoglobin digests WANG Tingting, LIANG Zhen, ZHANG Lihua, ZHANG Yukui 2010, 28 (3):  236-239.  DOI: 10.3724/SP.J.1123.2010.00236 Abstract ( 2874 )   [Full Text(HTML)] () PDF (153KB) ( 636 )   The monolithic polylaurylmethacrylate column was prepared in a single step using the monomer solution containing lauryl methacrylate (LMA), ethylene dimethacrylate (EDMA), and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), with the ternary porogenic solvent consisting of 1-propanol, 1,4-butanediol and H2O. The effects of AMPS content and the ratio of monomer solution to porogenic solvent were investigated. The optimal mass ratio of monomer solution to porogenic solvent was 35:65, the monomer solution was composed of 59.5%（w/w） LMA, 40%（w/w） EDMA and 0.5%（w/w） AMPS, and the porogenic solution was composed of 60%（w/w） 1-propanol, 30%（w/w） 1,4-butanediol and 10%（w/w） H2O. The prepared monolithic column was successfully applied in the capillary electrochromatographic (CEC) separation of myoglobin digests under the optimized mobile phase.

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Fast determination of active components in Angelica dahurica extract using capillary electrochromatography with methacrylate ester-based monolithic columns WANG Jiajing, CHEN Zhao, WU Yutian, FAN Guorong 2010, 28 (3):  240-246.  DOI: 10.3724/SP.J.1123.2010.00240 Abstract ( 2494 )   [Full Text(HTML)] () PDF (356KB) ( 668 )   The separation and determination of four important active components (imperatorin, isoimperatorin, phelloptorin and falcarindiol) from Angelica dahurica extract has been performed using capillary electrochromatography (CEC) with a methacrylate ester-based monolithic column. The effect of the porogen ratio on the column preparation was studied. The mobile phase composition, such as the concentration of organic solvent, the ionic strength and the pH of the buffer were also optimized. Under the optimized conditions (50% acetonitrile and 50% of a 20 mmol/L sodium dihydrogen phosphate electrolyte at pH 4.95, －25 kV), a fast and baseline separation of the four analytes was achieved. The calibration curves showed a good linearity (r2 ＞0.997) and the limits of detection were lower than 0.34 mg/L. The mean recoveries of the studied components ranged between 95.18% and 98.44%. The method developed is sensitive, reliable and suitable for the quality control. With this CEC system, the quality of Angelica dahurica extracts from 18 various regions was evaluated.

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Rapid analysis of trace levels of riboflavin and its derivatives with hydrophilic interaction monolith by pressurized capillary electrochromatography with laser induced fluorescence detection WU Yimin, WU Qingzheng, WANG Xiaochun, XIE Zenghong, WU Xiaoping 2010, 28 (3):  247-252.  DOI: 10.3724/SP.J.1123.2010.00247 Abstract ( 2783 )   [Full Text(HTML)] () PDF (235KB) ( 691 )   A novel hydrophilic interaction capillary electrochromatographic (HI-CEC) monolith with covalently bonded zwitterionic functional groups was applied for the separation of riboflavins (RF) and its derivatives. With a homemade pressurized capillary electrochromatography-laser induced fluorescence detection (pCEC-LIF) system, trace levels of RF and its derivatives, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), can be baseline separated within 8.0 min in isocratic elution mode. The effect of experimental parameters on separation was investigated. Under the optimum conditions, analytes could be determined over nearly three orders of magnitudes with the detection limits (LODs) as low as 5.0×10~11mol/L (RF), 8.0×10－10mol/L (FMN), 2.5×10－9mol/L (FAD), and the relative standard deviations (RSDs) were less than 8.2%. This method is rapid, simple, repeatable and more sensitive than the most of reported methods, and satisfied results has been achieved in serum sample. Furthermore, it can be further applied for trace analysis of RF and its derivatives in biological fluid and cells.

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Analysis of diuretics by capillary electrochromatography using poly(1-hexadecene-co-TMPTMA) monolithic column LU Minghua, LI Xin, FENG Qiang, CHEN Guonan, ZHANG Lan 2010, 28 (3):  253-259.  DOI: 10.3724/SP.J.1123.2010.00253 Abstract ( 2824 )   [Full Text(HTML)] () PDF (278KB) ( 731 )   A new method for analyzing diuretics by capillary electrochromatography using poly(1-hexadecene-co-TMPTMA) monolithic column was established. Experimental conditions including the mobile phase, separation voltage, and injection condition were optimized for the analysis. Under optimized experimental conditions, six diuretics were separated within 11.0 min with the limits of detection （LODs） (S/N=3) in the range of 0.35－0.65 μg/mL. The method showed good linearity (R2≥0.9908) in the range 1.15 and 86.0 μg/mL. The recoveries obtained from the analysis of spiked urine sample were between 81.9% and 105% with the relative standard deviations (RSDs) lower than 4.7%. It can be concluded that this new method possessed good repeatability and stability in analyzing diuretics, and was successfully applied to the analysis of real urine samples from volunteers. Therefore, this method could be applied to scanning diuretics in human urine samples.

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Separation performance of 1-μm silica particles as stationary phase for pressurized electrochromatography QU Qishu, ZHOU Yu, PENG Shengwei, HU Xiaoya, YAN Chao 2010, 28 (3):  260-263.  DOI: 10.3724/SP.J.1123.2010.00260 Abstract ( 2634 )   [Full Text(HTML)] () PDF (164KB) ( 653 )   Bare nonporous silica particles with diameter around 1 μm were prepared. A 20 cm section of a total length of 45 cm capillary (100 μm i.d.) was packed electrokinetically and the separation performance of basic compounds was investigated in the pressurized capillary electrochromatography (pCEC) system using 1 μm nonporous bare silica spheres as stationary phase and acetonitrile-water as mobile phase. The effects of the composition of the mobile phase, the concentration of the buffer, pH value, applied voltage and so on on the separation performance were investigated. The experimental results demonstrated that the bare silica column showed a typical reversed phase separation mechanism when it was used for separation of basic compounds. The separation performance changed slightly with changing buffer concentration. Since the degree of dissociation of the basic compounds depended greatly on the pH value, the interaction between the compounds and stationary phase changed with the changing of pH value, thereby changing the resolution of the compounds. The separation performance increased with the increase of applied voltage. A column efficiency of 35000 for o-toluidine was obtained when a voltage of 1 kV was applied.

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Microchip electrochromatography: the latest developments and applications WANG Junhua, HUANG Weihua, LI Lingjun, CHENG Jieke 2010, 28 (3):  264-272.  DOI: 10.3724/SP.J.1123.2010.00264 Abstract ( 2612 )   [Full Text(HTML)] () PDF (505KB) ( 799 )   This review summarizes recent developments and applications of microchip electrochromatography (μCEC) mainly in the past five years between 2005 and 2009 with a focus on column technologies. In addition, some new improvements in the chip design and fabrication, sample preconcentration, electroosmotic flow control as well as mechanisms that govern electrochromatographic separation are described and reviewed. The features and limitations of several practical aspects of their applications are highlighted.

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Recent advances in capillary electrochromatography and its coupling techniques LIN Zian, PANG Jilei, HUANG Hui, ZHANG Lan, CHEN Guonan 2010, 28 (3):  273-283.  DOI: 10.3724/SP.J.1123.2010.00273 Abstract ( 2744 )   [Full Text(HTML)] () PDF (519KB) ( 674 )   As a novel micro-separation technique, capillary electrochromatography (CEC) has the merits of high efficiency, high selectivity, high resolution and rapid analysis. However, the small-volume injection manipulated in capillary dimensions poses a great challenge for detectors in achieving high sensitivity. Currently, one of the major researches into CEC involves the development of some sensitive detection modes. The general introduction, which includes the historical perspectives and the principles of CEC, is briefly described. The recent advances about CEC coupled with various detectors and its applications in the separation of complex samples are summarized. A total of 141 references are reviewed.

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Recent advances in column for hydrophilic interaction capillary electrochromatography LIN Xucong, LIN Jia, WANG Jiabin, WANG Xiaochun, ZHANG Xiaowei, WANG Xiao, XIE Zenghong 2010, 28 (3):  284-290.  DOI: 10.3724/SP.J.1123.2010.00284 Abstract ( 2583 )   [Full Text(HTML)] () PDF (223KB) ( 776 )   Hydrophilic interaction capillary electrochromatography (HI-CEC) is one of the hot spots in micro-separation technique, and the research of HI-CEC stationary phase has attracted much attention. In this paper, the research progress of open-tubular column, the particle-packed column and the monolithic column for HI-CEC are reviewed, especially for the recent progress of the monolithic CEC.

Articles

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Preparation of bovine serum albumin immobilized adsorbent for specific adsorption of bilirubin YU Zhiyuan, WU Ren’an, ZOU Hanfa 2010, 28 (3):  291-295.  DOI: 10.3724/SP.J.1123.2010.00291 Abstract ( 2558 )   [Full Text(HTML)] () PDF (255KB) ( 597 )   Serum bilirubin concentration is greatly elevated in certain diseases such as hyperbilirubinemia and severe hepatitis. Lowering the level of bilirubin is one of the major targets of many therapies such as plasma exchange and hemoperfusion. In this study, a bilirubin specific adsorbent was prepared by covalently immobilizing bovine serum albumin (BSA) onto macroporous poly(glycidyl methacrylate-co-trimethylolpropane trimethacrylate) microspheres. The resulting BSA immobilized adsorbent (BIA) demonstrated good performance in adsorption of bilirubin with an adsorption capacity of 48.7 mg/g. Presence of BSA in bilirubin solution significantly lowered the adsorption capacity of the adsorbent due to the tight binding of bilirubin onto BSA. Adsorption performance of the adsorbent for bilirubin was improved with the elevation of temperature. The adsorbent demonstrated good stability even after 31 d of storage at －80 ℃ in that there was almost no change in adsorption capacity for bilirubin. These results indicated that the prepared BSA immobilized adsorbent could be an alternative choice for specific adsorption of bilirubin.

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Separation of proteins on microchip electrophoresis and its comparison with DNA migration LIU Chunye, XU Xu, ZHANG Jian, CHEN Jierong 2010, 28 (3):  296-300.  DOI: 10.3724/SP.J.1123.2010.00296 Abstract ( 2515 )   [Full Text(HTML)] () PDF (189KB) ( 507 )   The efficient separation of six standard proteins on a home-made poly(dimethylsiloxane) microchip with an auto-deducting background diode laser induced fluorescence detector was accomplished within 6.4 min under the sieving matrix of 10 g/L hydroxyethyl cellulose (HEC), 1 g/L sodium dodecyl sulphonate (SDS), 40 mmol/L phosphate buffer at pH 7.0. The experimental results showed that the reproducibility of protein separation was satisfactory and the relative standard deviations (RSDs) of protein migration time were less than 10%. The migration times of the proteins are analyzed by a quantitative mathematical model of deoxyribonucleic acid (DNA) proposed by ourselves previously. The results showed that the migration character of SDS-protein complexes was similar with DNA. However, the linear relationships between the mobilities of SDS-protein complexes and their relative molecular mass as well as electric field strength became worse, which indicated the mathematical model for DNA separation should be revised before it is used for protein separation.

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Determination of amitrole in agricultural products by high performance liquid chromatography-tandem mass spectrometry LI Li, FU Jian, GAO Hongliang, REN Haitao, LOU Xishan, GUAN Lihui 2010, 28 (3):  301-304.  DOI: 10.3724/SP.J.1123.2010.00301 Abstract ( 2715 )   [Full Text(HTML)] () PDF (140KB) ( 656 )   A high performance liquid chromatography-tandem mass spectrometry method (HPLC-MS/MS) was developed for the analysis of amitrole residues in agricultural products. The samples were extracted by 25% acetone for wheat, fish, pork and liver samples, 1% acetic acid-25% acetone for maize and peanut samples, 1% acetic acid solution for honeysuckle, the powder of ginger, the powder of bunge prickly ash and tea leaves samples, 1% acetic acid solution-dichloromethane for apple, pineapple, spinach, carrot, perilla leaves samples, respectively, followed by liquid-liquid extraction with dichloromethane. The samples were then cleaned up by PCX or Envi-Carb solid-phase extraction cartridge. The amitrole was determined and confirmed by HPLC-MS/MS. The results showed a linear relationship in the range of 0.005－0.1 mg/kg for amitrole. The correlation coefficient was 0.9997. The average recoveries of amitrole in wheat, maize, peanut, pineapple, apple, carrot, spinach, pork, the powder of ginger, the powder of bunge prickly ash, perilla, liver, fish, honeysuckle and tea were 67.5%－98.1%. The relative standard deviations (RSDs) were 1.0%－9.8%. The limits of quantitation were 10μg/kg for wheat, maize, peanut, pineapple, apple, carrot, spinach, pork, perilla, liver, fish, honeysuckle and 20μg/kg for the powder of bunge prickly ash, the powder of ginger and tea, respectively. The method is simple, sensitive and accurate.

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Enantioseparation of 1,1′-bi-2-naphthol benzoates using high performance liquid chromatography WANG Lili, XU Xiaojing, CHEN Guiyang, RUAN Yuanping 2010, 28 (3):  305-310.  DOI: 10.3724/SP.J.1123.2010.00305 Abstract ( 3420 )   [Full Text(HTML)] () PDF (251KB) ( 574 )   The enantioseparations of 2′-hydroxy-1,1′-binaphthyl-2-yl benzoate (HBNB), 1,1′-binaphthyl-2,2′-diyl dibenzoate (BNDB) and 2′-methoxy-1,1′-binaphthyl-2-yl benzoate (MBNB) were studied on Chirex (S)-LEU & (S)-NEA, cellulose tris(3,5-dimethylphenylcarbamate) (Chiralcel OD-H) and amylose tris(3,5-dimethylphenyl- carbamate) (Chiralpak AD-H) columns, respectively, using high performance liquid chromatography. The effects of mobile phase, column temperature and compound structures on the enantioseparations were discussed. The Chiralpak AD-H exhibited stronger capability of enantioseparation in comparison with those of Chirex (S)-LEU & (S)-NEA and Chiralcel OD-H for 1,1′-bi-2-naphthol benzoates. When using the mobile phase of n-hexane/2-propanol (40/60, v/v), the chiral selectivities of HBNB, BNDB and MBNB were 1.76, 1.74, and 1.40, respectively. Moreover, in comparison with that of 1,1′-bi-2-naphthol (BN), the mechanisms of the enantioseparation of 1,1′-bi-2-naphthol benzoates, related to the substituted groups at 2-position, the elution orders and thermodynamic parameters were also discussed.

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Optimization of L-glutamic acid racemization reaction with capillary array electrophoresis LIU Kaiying, BAI Jiling, WANG Li 2010, 28 (3):  311-315.  DOI: 10.3724/SP.J.1123.2010.00311 Abstract ( 2561 )   [Full Text(HTML)] () PDF (200KB) ( 510 )   L-Glutamic acid (Glu) racemization research is of great importance for the preparation of optical pure D-Glu. In the present work, we studied L-Glu racemization reaction through Schiff base intermediate by using capillary array electrophoresis (CAE) with 532 nm laser-induced confocal fluorescence detection. The racemization products were labeled by carboxytetramethylrhodamine succinimidyl ester (TAMRA) and analyzed in a 100 mmol/L Tris-borate buffer (pH 10) system containing 2 mmol/L β-CD by CAE. Under this condition, the TAMRA-Glu enantiomer can be completely separated. The influences of the type and dosage of the aldehyde, organic acids, as well as the water content in the reaction system on the racemization were examined in detail, and L-Glu was racemized quickly in the presence of 0.2 molar ratio of L-Glu to salicylaldehyde (as the catalyzer) in acetic acid containing 20%(v/v) water.

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Determination of pentostatin in culture broth using high performance liquid chromatography-mass spectrometry YANG Peng, WANG Yan, LIAO Yanyan 2010, 28 (3):  316-318.  DOI: 10.3724/SP.J.1123.2010.00316 Abstract ( 2863 )   [Full Text(HTML)] () PDF (108KB) ( 651 )   A method for the determination of pentostatin in culture broth was established using high performance liquid chromatography-mass spectrometry (HPLC-MS). The chromatographic conditions used were as follows: the analytical column was Hypersil ODS2 (250 mm×4.6 mm, 5 μm); the mobile phase was methanol/acetonitrile/10 mmol/L ammonium acetate (pH 7.6) (2.5/2.5/95, v/v/v) with a flow rate of 1.0 mL/min; the detection wavelength was 280 nm; the injection volume was 10 μL; the temperature was 40 ℃. The linear range of the method for pentostatin was 1.0－100 mg/L (r=0.9999). The method is characterized by simplicity, higher sensitivity and accuracy.

Technical Notes

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Determination and confirmation of cyanuric acid ininfant formula using mixed-mode solid-phase extraction cartridge clean up-gas chromatography-mass spectrometry LI Fengge, YAO Weiqin, TIAN Yanhe, DOU Hui, SU Min, ZHU Huiping, LI Xin, SHEN Mengyuan 2010, 28 (3):  319-322.  DOI: 10.3724/SP.J.1123.2010.00319 Abstract ( 2712 )   [Full Text(HTML)] () PDF (140KB) ( 539 )   A method is presented for the quantitative determination and confirmation of cyanuric acid in infant formula by mixed-mode solid-phase extraction cartridge clean up-gas chromatography-mass spectrometry (GC-MS). Cyanuric acid was extracted from infant formula with an acetic acid solution at 84 ℃. An aliquot of the supernatant was cleaned up using mixed-mode solid-phase extraction cartridge containing C18 and graphitized carbon black (GCB), and evaporated to dryness under nitrogen. The residues were converted to trimethylsilyl derivatives, then determined by GC-MS in selected ion monitoring (SIM) mode. The linear range was from 0.01－2 mg/L. The recoveries were 80%－103% and the relative standard deviations were 7.7%－14.5% in the spiked range of 0.25－2.5 mg/kg. The limit of detection was 0.10 mg/kg and the limit of quantification was 0.25 mg/kg. The method is rapid, sensitive, accurate, specific, and rugged. It is suitable for the quantitative determination and confirmation of cyanuric acid in infant formula.

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Simultaneous determination of various aseptics and sweeteners in milk and dairy products SONG Ge, JIANG Jindou, ZHANG Qiumei 2010, 28 (3):  323-326.  DOI: 10.3724/SP.J.1123.2010.00323 Abstract ( 3029 )   [Full Text(HTML)] () PDF (137KB) ( 632 )   A method for simultaneous determination of acesulfame, benzoic acid, sodium saccharin, sorbic acid, and aspartame in milk and dairy products using high performance liquid chromatography (HPLC) was developed. The proteins in milk and dairy products were mostly eliminated by the precipitators. Three aseptics and two sweeteners were separated on a C18 column with the mobile phase of methanol-0.05 mol/L potassium dihydrogen phosphate under gradient elution. With a diode array detector, acesulfame, benzoic acid, and sorbic acid were detected at 230 nm and sodium saccharin and aspartame were detected at 210 nm. The recoveries were 96.0%－103.5% with the relative standard deviations (RSDs) in the range of 1.93%－2.76%. The detection limits of acesulfame, benzoic acid, sodium saccharin, sorbic acid and aspartame were 1.0, 1.0, 0.5, 1.0, and 1.5 μg/g, respectively. This method can be used for the routine analysis of these additives in milk and dairy products.