A novel method for rapid determination of risperidone in human plasma using Reversed-Phase Liquid Chromatography with...

A simple and sensitive High-Performance Liquid Chromatographic (HPLC) method with UV detection is described for the quantitation of risperidone in human plasma, using bisoprolol as internal standard.

After sample alkalinization with 900 µl of NaOH, the test compounds were extracted from plasma using diethylether. The tubes were centrifuged twice and an evaporation to dryness under a gently stream of nitrogen at 50°C (~10 min) was done. 50 μl of the solution was injected into a C18 Nucleosyl analytical column (5 μm, 150×4.6 mm I.D). The mobile phase consisted of phosphate buffer (10 mM, pH 4.9 and 30% acetonitrile, (70:30, v/v), and was delivered at a flowrate of 1.0 ml/min.

The peaks were detected using a UV detector set at 279 nm and the total time for a chromatographic separation was about 8 min. This new method was validated for the concentration range 5-150 ng/ml. Mean recoveries were 92 % for risperidone. Intra- and inter-day relative standard deviations were less than 15% for our compound, while accuracy, expressed as percent error, ranged from 0.13 to 19 %. The limit of quantitation (LLOQ) was 3.23 ng/ml for the analyte.

The method shows good specificity with respect to commonly prescribed psychotropic drugs.