Determination of glimepiride in human plasma using semi-microbore high performance liquid chromatography with column-switching.

A fully automated semi-microbore high performance liquid chromatographic (HPLC) method with column-switching using UV detection was developed for the determination of glimepiride from human plasma samples. Plasma sample (900 microl) was deproteinated and extracted with ethanol and acetonitrile. The extract (70 microl) was directly injected into a Capcell Pak MF Ph-1 pre-column where the primary separation occurred to remove proteins and retain drugs using a mixture of acetonitrile and 10mM phosphate buffer (pH 2.18) (20:80, v/v). The analytes were transferred from the pre-column to an intermediate column using a switching valve and then subsequently separated on an analytical column and monitored with UV detection at 228 nm. Glimepiride was eluted with retention time 34.9 min without interference of endogenous substance from plasma. The limit of quantification (LOQ) was 10 ng/ml for glimepiride. The calibration curves were linear over the concentration range of 10-400 ng/ml (r(2) = 0.9997). Moreover, inter- and intra-day precisions of the method were less than 15% and accuracies were higher than 99%. The developed method was successfully applied for the quantification of glimepiride in human plasma and was used to support a human pharmacokinetic study following a single oral administration of 2 mg glimepiride.