Specific spectrofluorometric quantification of D-penicillamine in bulk and dosage forms after derivatization with 4-fluoro-7-nitrobenzo-2-oxa-1,3-diazole

A specific and sensitive fluorometric method is proposed for the determination of D-penicillamine in pure form and pharmaceuticals. The method is based on coupling between D-penicillamine and 4-fluoro-7-nitrobenzo-2-oxa-1,3-dizole (NBD-F) to produce the corresponding fluorescent NBD-penicillamine. The optimum conditions for the reaction were carefully investigated and incorporated into the procedure. The reaction was proceeded in berate buffer (pH 7.2) containing 20% of ethanol to give intense fluorescence having its excitation and emission wavelengths at 465 and 530nm, respectively. The fluorescence intensity was a linear function of the drug concentration over the range of 0.6-3 mu g ml(-1). Regression analysis of the concentration fluorescence intensity showed good correlation (r = 0.9975) with a detection limit of 2 x 10(-3) mu g ml(-1) (1.3 x 10(-8) M). The mean of percentage recoveries of added authentic drug was 100.00 +/- 1.05. The method was applied successfully to the determination of this drug in pharmaceutical dosage form. The mean recovery for the commercial capsules was 98.1 +/- 0.54%. The results were sufficiently accurate, precise and comparable with those obtained from the official method. The method is specific for the intact drug, and can be adopted in the presence of possible interferences. (C) 2000 Elsevier Science B.V. All rights reserved.