New assay method for the determination of vinpocetine in human plasma with gas chromatography-mass spectrometry without transesterification caused by solvents

New HPLC–MS method for quantitative determination of apovincaminic acid in human plasma

A fast and sensitive HPLC-MS method for the quantification of apovincaminic acid, a vinpocetine metabolite, in human plasma has been developed and validated. After protein precipitation with methanol, 10 mL of supernatant was injected at 45 degrees C onto a Zorbax SB-C18 column. Elution was performed in less than three minutes with water containing 0.2% formic acid and acetonitrile (80:20) at 0.75 mL/min. A linearity domain between 4 and 240 ng/mL and a limit of quantification of 4 ng/mL apovincaminic acid were established by monitoring the signal corresponding to m/z = 323. Accuracy and precision were less than 5.2% for within-run assay and 10% for between-run assay. The method was successfully applied in a bioequivalence study of two pharmaceutical products containing 5 mg vinpocetine.

Spectrophotometric and liquid chromatographic determination of fenofibrate and vinpocetine and their hydrolysis products

Several spectrophotometric and HPLC methods are presented for the determination of fenofibrate, vinpocetine and their hydrolysis products. The resolution of either fenofibrate or vinpocetine and their hydrolysis products has been accomplished by using numerical spectrophotometric methods as partial least squares (PLS-1) and principal component regression (PCR) applied to UV spectra; and graphical spectrophotometric methods as first derivative of ratio spectra (1DD) or first (1D) and second (2D) derivative spectrophotometry for vinpocetine and fenofibrate, respectively. In addition HPLC methods were developed using ODS column with mobile phase consisting of acetonitrile-water (80:20, v/v, pH 4) with UV detection at 287 nm for fenofibrate and a mobile phase consisting of acetonitrile-10 mM KH2PO4, containing 0.1% diethylamine (60:40, v/v, pH 4.6) with UV detection at 270 nm for vinpocetine. The proposed methods were successfully applied for the determination of each drug and its hydrolysis product in laboratory-prepared mixture and pharmaceutical preparation. The proposed HPLC and derivative spectrophotometric methods were used to investigate the kinetics of acidic and alkaline hydrolytic processes of each drug. The pH-rate profile of hydrolysis of each drug in Britton-Robinson buffer solutions was studied.

Improved gas chromatographic-mass spectrometric method for the quantitative determination of vinpocetine in human plasma

An improved and validated method for the determination of vinpocetine in human plasma using a combination of a solid-phase extraction as a cleaning step followed by gas chromatography-mass spectrometry (GC-MS) has been presented. Quantitation has been carried out with apovincaminic acid methyl ester as internal standard. A limit of detection of 0.01 ng/ml, limit of quantitation of 0.10 ng/ml, as well as a satisfactory accuracy, improved precision and prolonged capillary column life have been achieved.