[Determination of naphthidrofuryl and naphthidrofurylic acid in human plasma using RP-HPLC and fluorimetric detection].

An analytical method was developed for the determination of naphthidrofuryl and its principle metabolite--naphthidrofurylic acid in human plasma by the RP-HPLC method with fluorimetric detection. The analytical method is based on a single extraction with a 5 ml mixture ether: hexane (1:1 by volume), with salting out by means of potassium chloride after which the organic phase after centrifugation, evaporation and reconstitution is sprayed on the reverse phase of HPLC and the separated substances are determined fluorimetrically (excitation 271 nm, emission 240 nm). Lonazolac served as the internal standard. The mobile phase consisted of 72% methanol, 1% triethylamine, 0.6% phosphoric acid. Optimization of the composition of the mobile phase from the aspect of the amino base, dependence of the percent content of methanol in the mobile phase and dependence of the recovery of substances on the composition of the extracting reagent are presented. The limit of detection was 4 ng/ml of plasma for naphthidrofuryl. The stability of compounds (a minimum of 2 months) and interference of some other drugs are shown.