Analysis of tofisopam in human serum by column-switching semi-micro high-performance liquid chromatography and evaluation of tofisopam bioequivalency

A rapid and sensitive column-switching semi-micro HPLC method is described for the direct analysis of tofisopam in human serum. The sample (100 muL) was directly injected onto the precolumn (Capcell Pak MF Ph-1), where unretained proteins were eluted to waste. Tofisoparn was then eluted into an enrichment column using 13% acetonitrile in 50 mM phosphate buffer (pH 7.0) containing 5 mm sodium octanesulfonate and subsequently into the analytical column using 43% acetonitrile in 0.1% phosphoric acid containing 5 mm sodium octanesulfonate. The detection limit (2 ng/mL), good precision (CV less than or equal to 4.2%) and speed (total analysis time 24 min) of the present method were sufficient for drug monitoring. This method was successfully applied to a bioequivalence test of two commercial tofisopam tablets. Copyright (C) 2002 John Wiley Sons, Ltd.