Determination of glimepiride in human plasma by LC-MS-MS and comparison of sample preparation methods for glimepiride

A sensitive and selective method for quantitation of glimepiride in human plasma was established using liquid chromatography-electrospray ionization tandem mass spectrometry. Three different methods for the sample preparation of glimepiricle and an internal standard were investigated (liquid-liquid extraction, solid-phase extraction and protein precipitation). Glipizide was used as an internal standard. Compounds were separated on a C-18 column with 80% acetonitrile and 20% deionized water (adjusted to pH 3.5 with acetic acid), as mobile phase at a flow rate of 200 muL min(-1). By use of multiple reaction monitoring mode in MS-MS with liquid-liquid extraction and solid-phase extraction, glimepiricle and glipizide were detected without severe interference from the human plasma matrix. Glimepiride produced a protonated precursor ion ([M+H](+)) at m/z 491 and a corresponding product ion at m/z 352, and the internal standard produced a protonated precursor ion ([M+H](+)) at m/z 446 and a corresponding product ion at m/z 321. The limit of quantitation was 0.1 ng mL(-1), 0.5 ng mL(-1) and 1.0 ng mL(-1) when using liquid-liquid extraction, solid-phase extraction and protein precipitation, respectively. The validation, reproducibility, stability, and recovery of the different sample preparation methods were comparable and all the methods gave reliable results. The method has been successfully applied to pharmacokinetic study of glimepiricle in human plasma.