The origin of pseudo peak was studied by means of micellar electrokinetic capillary chromatography with cetyltrimethylaminium bromide as the pseudo stationary phase. It has been pointed that two peaks may appear for o...The origin of pseudo peak was studied by means of micellar electrokinetic capillary chromatography with cetyltrimethylaminium bromide as the pseudo stationary phase. It has been pointed that two peaks may appear for one component under certain conditions. Experiments showed that the relative areas of the two peaks of analyte depended on the time and the temperature of reaction between analyte and surfactant, and the concentration of surfactant in the sample solution. It means that the interaction between the analyte and the surfactant is a slow process, and a stable substance can be produced from the interaction. It is the substance and the analyte that may lead to the formation of two peaks. The fast interaction mechanism between the solute and the micellar should be queried from the experiment result.展开更多
A micellar electrokinetic capillary chromatography (MECC) was developed for the determination of aniline and 6 substituted anilines. The seven components were separated within 25 min in the buffer solution of 40 mmol/...A micellar electrokinetic capillary chromatography (MECC) was developed for the determination of aniline and 6 substituted anilines. The seven components were separated within 25 min in the buffer solution of 40 mmol/L sodium borate and 100 mmol/L SDS. It was found that the separation was dependent on operating voltage, pH value, borate and SDS concentrations. The analytical performance was examined in terms of linear response and reproducibility. Wastewater was determined by the established method.展开更多
A sensitive method for simultaneous determination of six phenolic whitening agents, including arbutin, phenol, resorcinol, hydroquinone, kojic acid, and salicylic acid in cosmetics has been developed using micellar el...A sensitive method for simultaneous determination of six phenolic whitening agents, including arbutin, phenol, resorcinol, hydroquinone, kojic acid, and salicylic acid in cosmetics has been developed using micellar electrokinetic capillary chromatography with amperometric detection （MECC-AD）. Effects of several factors, such as the pH value and concentration of running buffer, potential applied to the working electrode, separation voltage, and injection time were investigated to obtain optimum conditions for separation and detection. With a 75 cm long fused-silica capillary tube, well-defined separation of six phenolic compounds was achieved in 10 mmol/L SDS/40 mmol/L H3BO3-Na2B407 running buffer （pH 9.0）. Good linear relationship was obtained for each analyte over three orders of magnitude with correlation coefficients （r2） between 0.9985 and 0.9994, and the detection limit （S/N = 3） ranged from 0.04 p^g/mL to 0.45 p^g/mL. The proposed method has been successfully applied for the determination of phenolic whitening agents in real cosmetic samples with satisfactory results, providing an alternative monitoring method for cosmetics safety regulation.展开更多
Central composite design(CCD),together with multiple linear regression,was successfully used to optimize the electrophoretic buffer system of micellar electrokinetic capillary chromatography(MEKC) for the determinatio...Central composite design(CCD),together with multiple linear regression,was successfully used to optimize the electrophoretic buffer system of micellar electrokinetic capillary chromatography(MEKC) for the determination of albiflorin,paeoniflorin,liquiritin,and glycyrrhizic acid in the traditional Chinese medicine(TCM) prescription,Yangwei granule.Concentrations of sodium deoxycholate(SDC) and borate,and proportions of ammonia,acetonitrile,and methanol were optimized.The total resolutions of peaks between the analytes and their adjacent peaks in real samples were integrated into the evaluation index of separation efficiency.The optimum electrophoretic buffer contained 80 mmol/L SDC,20 mmol/L borate,5%(v/v) methanol,0.5%(v/v) ammonia,and 5%(v/v) acetonitrile.The correlation coefficients(R 2 ) between the peak areas and the corresponding concentrations of analytes were greater than 0.9956.The limits of detection(LODs) (S/N=3) of the analytes were 0.97-4.00μg/ml.The results indicate the superiority of CCD in optimizing the separation conditions of complex samples such as TCM prescriptions.展开更多
The formation origin of two peaks in micellar electrokinetic capillary chromatography by using cetyltrimethylaminium bromide (or sodium dodecyl sulfate) as pseudo stationary phase is studied. It is pointed out that tw...The formation origin of two peaks in micellar electrokinetic capillary chromatography by using cetyltrimethylaminium bromide (or sodium dodecyl sulfate) as pseudo stationary phase is studied. It is pointed out that two peaks may appear for one component in certain conditions. Experiments show that the relative areas of the two peaks of the corresponding component depend on the time and temperature of reaction between the analyte and the surfactant, and the concentration of surfactant in the sample solution. One of the two peaks increase with the increase of surfactant concentration in the sample solution while reverse for another peak. Temperature can accelerate the reaction process. This means that the interaction between analyte and surfactant is a slow process, and a stable substance can be produced from the interaction and leads to the formation of two peaks. The standpoint is confirmed by the infrared and nuclear magnetic resonance spectra of the product from the reaction between cetyltrimethylaminium bromide and m-hydroxyl benzoic acid.展开更多
A facile micellar electrokinetic chromatography(MEKC) method was developed for quantification of aromatic amino acids in Cordyceps fungi. The proposed MEKC method had linear calibration curves and detection limits at ...A facile micellar electrokinetic chromatography(MEKC) method was developed for quantification of aromatic amino acids in Cordyceps fungi. The proposed MEKC method had linear calibration curves and detection limits at the μmol/L level. Contents of aromatic amino acids in Cordyceps were found in the range from 0.004 9 % to 0.028 0% for tryptophan(Trp), 0.036 6% to 0.078 1% for tyrosine(Tyr), and 0.029 1% to 0.136 2% for phenylalanine(Phe). Levels of amino acids in cultivated Cordyceps militaris were found higher than those in natural Cordyceps sinensis. Interestingly, the ratio of Tyr to its precursor, Phe, in C. sinensis(1.20 ± 0.091, n=3) was significantly higher than that in cultivated C. militaris(0.54 ± 0.170, n=3). This is likely because the enzyme-catalyzed in vivo biotransformation of Phe to Tyr is much more effective in natural C. sinensis, a biological hybrid of larva and parasitic fungus, than in cultivated C. militaris.展开更多
基金Supported by the National Natural Science Foundation of China(No. 2 0 0 75 0 0 5 ) and the Natural Science Foundation ofHebei ProvinceChina(No. 2 0 0 0 77,2 0 2 0 96 )
文摘The origin of pseudo peak was studied by means of micellar electrokinetic capillary chromatography with cetyltrimethylaminium bromide as the pseudo stationary phase. It has been pointed that two peaks may appear for one component under certain conditions. Experiments showed that the relative areas of the two peaks of analyte depended on the time and the temperature of reaction between analyte and surfactant, and the concentration of surfactant in the sample solution. It means that the interaction between the analyte and the surfactant is a slow process, and a stable substance can be produced from the interaction. It is the substance and the analyte that may lead to the formation of two peaks. The fast interaction mechanism between the solute and the micellar should be queried from the experiment result.
文摘A micellar electrokinetic capillary chromatography (MECC) was developed for the determination of aniline and 6 substituted anilines. The seven components were separated within 25 min in the buffer solution of 40 mmol/L sodium borate and 100 mmol/L SDS. It was found that the separation was dependent on operating voltage, pH value, borate and SDS concentrations. The analytical performance was examined in terms of linear response and reproducibility. Wastewater was determined by the established method.
基金supported by the Natural Science Foundation of China(No.21205042)the Special Funds for the Development of Major Scientific Instruments and Equipment(No. 2011YQ15007205)
文摘A sensitive method for simultaneous determination of six phenolic whitening agents, including arbutin, phenol, resorcinol, hydroquinone, kojic acid, and salicylic acid in cosmetics has been developed using micellar electrokinetic capillary chromatography with amperometric detection （MECC-AD）. Effects of several factors, such as the pH value and concentration of running buffer, potential applied to the working electrode, separation voltage, and injection time were investigated to obtain optimum conditions for separation and detection. With a 75 cm long fused-silica capillary tube, well-defined separation of six phenolic compounds was achieved in 10 mmol/L SDS/40 mmol/L H3BO3-Na2B407 running buffer （pH 9.0）. Good linear relationship was obtained for each analyte over three orders of magnitude with correlation coefficients （r2） between 0.9985 and 0.9994, and the detection limit （S/N = 3） ranged from 0.04 p^g/mL to 0.45 p^g/mL. The proposed method has been successfully applied for the determination of phenolic whitening agents in real cosmetic samples with satisfactory results, providing an alternative monitoring method for cosmetics safety regulation.
基金Project supported by the National Science and Technology Major Project of Ministry of Science and Technology of China(No. 2009ZX09313-036)the Program for New Century Excellent Talents in University of Ministry of Education of China(No.NCET-06-0515)
文摘Central composite design(CCD),together with multiple linear regression,was successfully used to optimize the electrophoretic buffer system of micellar electrokinetic capillary chromatography(MEKC) for the determination of albiflorin,paeoniflorin,liquiritin,and glycyrrhizic acid in the traditional Chinese medicine(TCM) prescription,Yangwei granule.Concentrations of sodium deoxycholate(SDC) and borate,and proportions of ammonia,acetonitrile,and methanol were optimized.The total resolutions of peaks between the analytes and their adjacent peaks in real samples were integrated into the evaluation index of separation efficiency.The optimum electrophoretic buffer contained 80 mmol/L SDC,20 mmol/L borate,5%(v/v) methanol,0.5%(v/v) ammonia,and 5%(v/v) acetonitrile.The correlation coefficients(R 2 ) between the peak areas and the corresponding concentrations of analytes were greater than 0.9956.The limits of detection(LODs) (S/N=3) of the analytes were 0.97-4.00μg/ml.The results indicate the superiority of CCD in optimizing the separation conditions of complex samples such as TCM prescriptions.
基金This work was supported by the National Natural Science Foundation of China(Grant No.20075005) the Natural Science Foundation of Hebei Province,China(Grant Nos.200077 and 202096).
文摘The formation origin of two peaks in micellar electrokinetic capillary chromatography by using cetyltrimethylaminium bromide (or sodium dodecyl sulfate) as pseudo stationary phase is studied. It is pointed out that two peaks may appear for one component in certain conditions. Experiments show that the relative areas of the two peaks of the corresponding component depend on the time and temperature of reaction between the analyte and the surfactant, and the concentration of surfactant in the sample solution. One of the two peaks increase with the increase of surfactant concentration in the sample solution while reverse for another peak. Temperature can accelerate the reaction process. This means that the interaction between analyte and surfactant is a slow process, and a stable substance can be produced from the interaction and leads to the formation of two peaks. The standpoint is confirmed by the infrared and nuclear magnetic resonance spectra of the product from the reaction between cetyltrimethylaminium bromide and m-hydroxyl benzoic acid.
基金Supported by Zhongnan Hospital of Wuhan University Science,Technology,and Innovation Seed Fund(cxpy2017023)the TCM Research Project of Hubei Provincial Health Commission(ZY2019M033)
文摘A facile micellar electrokinetic chromatography(MEKC) method was developed for quantification of aromatic amino acids in Cordyceps fungi. The proposed MEKC method had linear calibration curves and detection limits at the μmol/L level. Contents of aromatic amino acids in Cordyceps were found in the range from 0.004 9 % to 0.028 0% for tryptophan(Trp), 0.036 6% to 0.078 1% for tyrosine(Tyr), and 0.029 1% to 0.136 2% for phenylalanine(Phe). Levels of amino acids in cultivated Cordyceps militaris were found higher than those in natural Cordyceps sinensis. Interestingly, the ratio of Tyr to its precursor, Phe, in C. sinensis(1.20 ± 0.091, n=3) was significantly higher than that in cultivated C. militaris(0.54 ± 0.170, n=3). This is likely because the enzyme-catalyzed in vivo biotransformation of Phe to Tyr is much more effective in natural C. sinensis, a biological hybrid of larva and parasitic fungus, than in cultivated C. militaris.
