Fluorometric Determination of Drugs Containing α-Methylene Sulfoxide Functional Groups Using - Methylnicotinamide Chloride as a Fluorogenic Agent

A simple fluorometric method, using 1-methylnicotinamide chloride (NMNCl) as a fluorogenic reagent, has been developed, adapted, and validated for the quantitative estimation of drugs containing α-methylene sulfoxide functional groups. The proposed method has been applied successfully to the determination of sulindac (1), omeprazole (2), lansoprazole (3), pantoprazole (4), and rabeprazole (5) in the pure form, laboratory-prepared mixtures, pharmaceutical dosage forms, spiked human plasma samples, and in hospitalized patient's or volunteer's blood. For the standard solutions of 1, 2, 3, 4, and 5, the method showed linearity over concentration ranging between 1–50 g/mL, 50–1200 ng/mL, 100–1500 ng/mL, 10–1500 ng/mL, and 20–2200 ng/mL, respectively. For the spiked human plasma of 1, 2, 3, 4, and 5, the linearity was shown over concentration ranging between 1–50 μg/mL, 75–1200 ng/mL, 100–1400 ng/mL, 10–1500 ng/mL, and 50–2100 ng/mL, respectively. The method showed good accuracy, specificity, and precision in both laboratory-prepared mixtures and spiked human plasma samples. The proposed method is simple, does not need sophisticated instrumentation, suitable for quality control application, bioavailability, and bioequivalency studies. Besides, the sensitivity and detection limits are comparable to sophisticated chromatographic methods.