Determination of Venlafaxine in Human Saliva by HPLC using Solid-Phase Extraction

The purpose of this study was to develop a sensitive and rapid method for the determination of venlafaxine in human saliva. Blank saliva samples were obtained from healthy volunteers. Their extraction was carried out on SPE columns. Cartridges of the columns were washed with water and the adsorbate was eluted with methanol. The eluate was evaporated and the residue was dissolved in a mixture of acetonitrile and water (50: 50, v/v). Venlafaxine was analyzed on a HPLC system with UV detection at 226 nm. The mobile phase was a mixture of acetonitrile and a phosphate buffer (30:70 v/v) at a flow rate of 1 mL min(-1). Linearity of the calibration curve was obtained in the range of 1-1000 ng mL(-1) of venlafaxine in saliva. The limit of detection was 1 ng mL(-1) (S/N = 3) and the limit of quantification was 3 ng mL(-1) (S/N = 10). The RSD values for intra-day study varied between 0.21 and 1.67% and those for inter-day study did not exceed 8.14%. The developed method was applied to the analysis of saliva samples without interference peaks and enabled determination of the venlafaxine concentration in depressed persons. The method can be useful for controlling intake of the drug by patients.