salicylates and caffeic-acid

A high-performance liquid chromatography coupled with photodiode-array spectrophotometry and electrospray ionization-mass spectrometry (HPLC-PDA-ESI-MS) method for separation and determination of phenolic acids in ethyl acetate extracts from Chinese waxberry (Myrica Rubra) juice was developed. Total of 4 phenolic acids (ferulic, caffeic, sinapic, and salicylic acids) were identified by comparing their HPLC retention times, UV-Vis absorption spectra, and simultaneously recorded mass spectra with authentic standards. Quantitation was carried out by the peak area method. The calibration curves are linear over the concentration range studied with the correlation coefficients, R(2), greater than 0.99. The contents of ferulic, caffeic, sinapic, and salicylic acids in waxberry juice samples studied were 2.76, 3.58, 2.89, and 1.92 mg/L, respectively, and they occur mainly in bound forms. All relative standard deviations were less than 4%. The recoveries range from 83.6% to 95.8% for the 4 analytes. To the authors' best knowledge, this is the first report for the identification of the sinapic and salicylic acids in Chinese waxberry products.

Topics: Beverages; Caffeic Acids; Calibration; Chromatography, High Pressure Liquid; Coumaric Acids; Myrica; Salicylates; Spectrometry, Mass, Electrospray Ionization; Tandem Mass Spectrometry

In the paper, a new kind of vitamin B(12) (acquo-cobalamine) chemically modified electrode was fabricated and applied in capillary zone electrophoresis coupled with amperometric detection (CZE-AD) for simultaneous determination of six antioxidants in fruits and vegetables. The catalytic electrochemical properties of the chemically modified electrode could obviously enhance oxidation peak heights responses by about five times to glutathione, ascorbic acid, vanillic acid, chlorogenic acid, salicylic acid, and caffeic acid compared with common carbon disk electrode. Furthermore, the effects of working electrode potential, pH and concentration of running buffer, separation voltage and injection time on CZE-AD were investigated. Under the optimum conditions, the six analytes could be completely separated and detected in a borate-phosphate buffer (pH 8.4) within 15 min. Their linear ranges were from 2.5x10(-7) to 1.0x10(-4) mol L(-1) and the detection limits were as low as 10(-8) mol L(-1) magnitude (S/N=3). The proposed method has been successfully employed to monitor the six analytes in practical samples with recoveries in the range 96.0-106.0% and RSDs less than 5.0%. Above results demonstrate that capillary zone electrophoresis coupled with electrochemical detection using vitamin B(12) modified electrode as detector is of convenient preparation, high sensitivity, good repeatability, and could be used in the rapid determination of practical samples.

Topics: Antioxidants; Ascorbic Acid; Caffeic Acids; Chlorogenic Acid; Citrus sinensis; Electrochemistry; Electrodes; Electrophoresis, Capillary; Glutathione; Hydrogen-Ion Concentration; Oxidation-Reduction; Reproducibility of Results; Salicylates; Solanum lycopersicum; Vanillic Acid; Vitamin B 12

An improved chemometric approach is proposed for assessing chromatographic peak purity by means of artificial neural networks. A non-linear transformation function with a back-propagation algorithm was used to describe and predict the chromatographic data. The Mann-Whitney U-test was used for the concluding the purity of the chromatographic peak. Simulation data and practical analytical data for both pure and mixture samples were analysed with satisfactory results. A prior knowledge of the impurity and the related compound is unnecessary when a slight difference between their chromatogram and spectrum exists. The performance on simulated data sets by this approach was compared with the results from principal component analysis.

Topics: Algorithms; Caffeic Acids; Chromatography; Hydrogen-Ion Concentration; Hydroxybenzoates; Neural Networks, Computer; Parabens; Salicylates; Salicylic Acid