Fully automated LC method for the determination of sotalol in human plasma using restricted access material with cation exchange properties for sample clean-up

A simple and rapid fully automated bio-analytical method for the liquid chromatographic (LC) determination of sotalol in human plasma has been described. The method is based on the use of a new kind of porous silica restricted access material (RAM) with cation exchange properties for sample clean-up. 100 mul of plasma samples were directly injected into the precolumn coupled on-line to a reversed-phase column (RP-Select 13) by means of column switching system. The plasma matrix was washed out for 10 min using a washing liquid composed of 2 mM lithium perchlorate and methanol (97:3; v/v). By rotation of the switching valve, the analytes, were then eluted in back-flush mode for 2 min and transferred to the analytical column by the LC mobile phase constituted of a mixture of methanol and 50 mM potassium phosphate buffer (pH 7.0) containing 1 mM 1-octanesulphonic acid sodium salt (20:80;.v/v). The flow-rate was 1.0 ml/min and sotalol was detected using fluorescence detection at 235 and 300 nm as excitation and emission wavelengths, respectively. The method was then validated using a new approach based on accuracy profile over a concentration range from 5 to 500 ng/ml. The limit of quantitation (LOQ) was 5 ng/ml and the total analysis time was 19 min. (C) 2003 Elsevier Science B.V. All rights reserved.