Determination of cycloserine in human plasma by high-performance liquid chromatography with fluorescence detection, using derivatization with p-benzoquinone

A new method for determining cycloserine in plasma samples is described. Th is method is based on the derivatization of cycloserine with p-benzoquinone , a reaction that takes place at the same time as the process of plasma dep roteinization due to the presence of ethanol as solvent in the solution of the derivatization reagent, Four derivatives are obtained from this reactio n. The main derivative is well correlated with the cycloserine concentratio n. The ratio between the volumes of the plasma sample and the reagent solut ion is 1:2 for a p-benzoquinone concentration of 1000 mug/mL. Elution from a C-18 column was isocratic, using a mobile phase containing (v/v) 85% aque ous 0.1% formic acid solution, and 15% (v/v) of a mixture of methanol and a cetonitrile (1:1), with a flow-rate of 1 mL/min, at 25 degreesC. Determinat ions by fluorescence detection were achieved with excitation at 381 nm and emission at 450 nm, with a detection limit of 10 ng/mL for an injection vol ume of 5 muL. This method was validated and applied to the determination of cycloserine in blood plasma samples of several healthy volunteers. (C) 200 1 Elsevier Science B.V. All rights reserved.