Spectrophotometric and spectrofluorimetric determination of mesna, acetylcysteine and timonacic acid through the reaction with acetoxymercuri fluorescein

Abstract

Simple, sensitive and specific spectrophotometric (Method I) and spectrofluorimetric (Method II) methods were developed for the determination of three sulfur-containing drugs: mesna (MSN), acetylcysteine (ACT) and timonacic acid (TMN). The methods are based on the suppressive effect of the drugs on the absorbance and the fluorescence intensity of 2′,7′-bis(acetoxymercuri)fluorescein (AMF) in 0.05 M borate buffer. In Method I the decrease in AMF absorbance was measured at 497 nm, while in Method II the fluorescence quenching of the reagent was measured at λ_em 520 nm (λ_ex 497 nm). All the experimental parameters affecting this reaction were studied and optimized. The selectivity and the stability-indicating aspect of the methods were confirmed and no interference was detected from the oxidation products of the quantified drugs or from other co-administered drugs. Method I was applicable over the concentration ranges 0.5–3, 0.5–2.75 and 0.25–2.75 μg mL⁻¹ for MSN, ACT and TMN, respectively. The reaction sensitivity was enhanced by Method II where the linearity ranges were found to be 0.6–7.2, 0.7–7 and 0.8–10.4 ng mL⁻¹ for MSN, ACT and TMN, respectively. Both methods were applied for the determination of the three drugs in bulk form and in their pharmaceutical preparations without interference from common excipients. The percentage recoveries were satisfactory and they were statistically compared with those obtained from previously reported methods. Moreover, Method II was extended to analyze the drugs in spiked human plasma, by virtue of its high sensitivity.