ABSTRACT
A liquid chromatography method with multi-channel electrochemical detection was developed for the determination of epigallocatechin gallate (EGCG) in rat plasma. After administration of EGCG, blood samples were periodically collected by Culex (an automated blood sampling robot). EGCG was extracted from 50 microl of diluted blood (blood and saline at a ratio of 1:1) with ethyl acetate. Chromatographic separation was achieved within 10 min using a C8 (150x4.6 mm) 5 microm column with a mobile phase containing 20 mM sodium monochloroacetate, pH 2.8 and 12% acetonitrile at a flow-rate of 1.2 ml/min. A four-channel detector with glassy carbon electrodes was used with applied potentials of +700, 600, 500, 400 mV vs. Ag/AgCl. The limit of detection was 2 ng/ml at a signal-to-noise ratio of 3:1 and the limit of quantitation was 5 ng/ml. The calibration curve was linear over the range of 5-800 ng/ml. The intra- and inter-assay precisions were in the range of 1.3-4.5% and 2.2-4.4%, respectively. Using this method it was possible to determine plasma concentration following a single dose of EGCG to rats with good accuracy and precision. Thus the pharmacokinetic properties of EGCG in rats can be examined for intravenous, intraperitoneal and oral dosing.
Subject(s)
Catechin/blood , Chromatography, Liquid/methods , Electrochemistry/methods , Animals , Catechin/analogs & derivatives , Catechin/pharmacokinetics , Rats , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
A sensitive and selective multichannel liquid chromatography-electrochemistry method was developed for the determination of the natural product trans-resveratrol (resveratrol) in rat blood. After administration of resveratrol, blood samples were periodically collected by an automated blood sampling device. Resveratrol was extracted from 150 microl of diluted blood (blood and saline at a ratio of 1:1) with acetonitrile containing 1% of trichloroacetic acid. Chromatographic separation was achieved within 12 min using a C18 (100x2.0 mm) 3 microm column with a mobile phase containing 20 mM sodium acetate, 0.5 mM EDTA, pH 4.5 and 21% acetonitrile at a flow-rate of 0.4 ml/min. A multichannel detector with glassy carbon electrodes was used, which can control up to four working electrodes simultaneously with applied potentials of +800, 700, 600, 500 mV vs. Ag/AgCl. The limit of detection was 2 ng/ml at a signal-to-noise ratio of 3:1 and the limit of quantitation was 4 ng/ml. The linearity of the calibration curve was obtained over the analytical range of 5-1000 ng/ml. The intra- and interassay precision was in the range of 2.5-4.4% and 1.2-4.3%, respectively. Using this method it was possible to quantify blood concentration following a single dose of resveratrol to rats with good accuracy and precision. Thus the pharmacokinetic properties of resveratrol in rats can be examined for intraperitoneal, oral and intravenous dosing.
Subject(s)
Chromatography, Liquid/methods , Stilbenes/blood , Animals , Automation , Calibration , Platelet Aggregation Inhibitors/analysis , Platelet Aggregation Inhibitors/blood , Quality Control , Rats , Reference Standards , Reproducibility of Results , Resveratrol , Stereoisomerism , Stilbenes/analysisABSTRACT
A liquid chromatographic method has been developed for the determination of 3-nitro-L-tyrosine. Different detection methods, including UV, oxidative and redox electrochemistry, and postcolumn photolysis followed by electrochemical detection, have been optimized and compared in terms of analysis time, detection limit and dynamic range. It was demonstrated that liquid chromatography with postcolumn photolysis followed by electrochemical detection is the most effective method, with an analysis time of 5 min, detection limit of 0.01 pmol, and a linear dynamic range from 2 nM to 100 microM.
