Analytical Sciences

Liquid Chromatographic Determination of Ethambutol in Serum Samples Based on Intramolecular Excimer-forming Fluorescence Derivatization

Yukitaka NAKANO,* Hitoshi NOHTA,** Hideyuki YOSHIDA,** Kenichiro TODOROKI,** Tetsuya SAITA,* Hiroshi FUJITO,* Masato MORI,* and Masatoshi YAMAGUCHI**

*Department of Pharmacy, Saga University Hospital, 5-1-1 Nabeshima, Saga 849-8501, Japan
**Faculty of Pharmaceutical Sciences, Fukuoka University, 8-19-1 Nanakuma, Johnan-ku, Fukuoka 814-0180, Japan

A selective liquid chromatographic method has been developed for the assay of ethambutol in serum samples. The assay involves intramolecular excimer-forming derivatization with 4-(1-pyrene)butanoyl chloride (PBC) and isocratic reversedphase chromatography with fluorescence detection. After acetonitrile-deproteinization of the serum sample, the derivatization reaction of ethambutol with PBC was completed within 30 min at 50°C. N,N′-Diethylethylenediamine was used as an internal standard. The detection limit of ethambutol was 23 ng/ml serum, corresponding to 180 fmol on column at a signal-to-noise ratio of 3. The present method was selective enough to analyze ethambutol in rabbit serum without any tedious sample clean-up procedure because biogenic monoamines gave no peak in the chromatogram. The method was applicable to drug monitoring in rabbit serum.

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