HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC DETERMINATION OF LEVODROPROPIZINE IN HUMAN PLASMA WITH FLUOROMETRIC DETECTION

The present paper describes a new high-performance liquid chromatograp hic method with fluorescence detection for the analysis of levodroprop izine S-(-)-3-(4-phenylpiperazin-1-yl)-propane-1,2-diol] (Levotuss), a n anti-tussive drug, in human serum and plasma. A reversed-phase separ ation of levodropropizine was coupled with detection of the native flu orescence of the molecule, using excitation and emission wavelengths o f 240 nm and 350 nm respectively. The analytical column was packed wit h spherical 5 mu m poly(styrene-divinylbenzene) particles and the mobi le phase was 0.1 M NaH2PO4 pH 3-methanol (70:30, v/v), containing 0.5% (v/v) tetrahydrofuran. For quantitation, p-methoxylevodropropizine wa s used as the internal standard. Samples of 200 mu l of either serum o r plasma were mixed with 200 mu l of 0.1 M Na2HPO4 pH 8.9 and extracte d with 5 ml of chloroform-2-propanol (9:1, v/v). The dried residue fro m the organic extract was redissolved with distilled water and directl y injected into the chromatograph. The limit of detection for levodrop ropizine, in biological matrix, was about 1-2 ng/ml, at a signal-to-no ise ratio of 3. The linearity was satisfactory over a range of concent rations from 3 to 1000 ng/ml (r(2)=0.99910); within-day precision test ed in the range 5-100 ng/ml as well as day-to-day reproducibility prov ed acceptable, with relative standard deviations better than 1% in mos t cases. Interferences from as many as 91 therapeutic or illicit drugs were excluded.