Jutima Boonleang

pp. 427 - 440

Abstract

Clarithromycin (CAM) is a semisynthetic macrolide antibiotic whose chemical structure has no suitable chromophore for highly sensitive and accurate direct determination. The aim of this study was to derivatize CAM with fluorescence-labeling compounds capable of enhancing the sensitivity of CAM determination. Two fluorescence-labeling compounds were used in this study, 9 fluorenylmethyloxycarbonyl chloride (FMOC-Cl) and 1-naphthylisocyanate (NIC), both of which gave the fluorescent derivatives of CAM with approximately the same fluorescence intensity. The derivatization reactions in the concentration range studied (0.1-2.4 µg/ml) were reproducible with coefficient of variation of less than 6.01% and the fluorescence responses were linearly proportional to CAM concentration with r² of greater than 0.99. The reaction of CAM with FMOC-Cl optimally occurred in a solvent mixture of acetonitrile and phosphate buffer pH 7.5 (4:1 volume ratio) at 40°C for 40 min. The optimum derivatization reaction of CAM with NIC took place in
acetonitrile with triethylamine as catalyst at 30°C for 60 min. It was mild and quantitative giving CAM-NIC fluorescent derivative, which is more stable at room temperature than CAM-FMOC derivative. This derivatization should, therefore, be more applicable for highly sensitive CAM determination especially for the study involving the analysis of several samples.