Analytical Sciences

Column-Switching HPLC Determination of Mexiletine Using Tris(bipyridine)ruthenium(III) Electrogenerated Chemiluminescence and Precolumn Derivatization with Divinylsulfone

Naoko KOBAYASHI,* Aoi MIYAMOTO,** and Kazuo UCHIKURA**

*Graduate School of Pharmacy, Nihon University, 7-7-1 Narashinodai, Funabashi, Chiba 274-8555, Japan
**School of Pharmacy, Nihon University, 7-7-1 Narashinodai, Funabashi, Chiba 274-8555, Japan

A sensitive HPLC method combined with a column-switching system and tris(bipyridine)ruthenium(III) electrogenerated chemiluminescence (ECL) detection has been developed for the quantitative determination of mexiletine (MEX). MEX was derivatized by divinylsulfone (DVS) and then measured. The optimum conditions for the derivatization reaction were 10 μL of sample solutions, 40 mM DVS (pH 8.0), a reaction temperature of 50°C, and a reaction time of 15 min. The derivatized samples were cleaned up by an on-line pretreatment column. Also, after column-switching to the analytical column, the derivatized MEX was separated and detected. The calibration curves of MEX in human control serum showed good linear regression (r = 0.9996) from 0.008 to 6.56 μg ml⁻¹. The detection limit of MEX was 0.008 μg ml⁻¹ (S/N = 3). At a concentration of 2.0 μg ml⁻¹ MEX, the relative standard deviation (n = 5) was 0.98%. In this method the concentration of MEX in human control serum was readily measured, and this method was successfully applied to the time courses of the concentration of MEX in rabbit plasma after intravenous administration. The proposed method involved a simple and minimum sample-preparation procedure and a short run time (<20 min). Therefore it can be applied to routine therapeutic monitoring and pharmacokinetic studies of MEX.

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