A highly sensitive fluorescent probe for tiopronin based on the cleavage of 2, 4-dinitrobenzenesulfonate

A highly sensitive fluorogenic probe for tiopronin was proposed. 2,4-Dinitrobenzenesulfonyl-fluorescein (I) is an almost nonfluorescent compound. Upon mixing with tiopronin in aqueous solution, the 2,4-dinitrobenzenesulfonyl group of I was efficiently removed and its parent dye fluorescein was released, hence leading to dramatic increases in both fluorescence and absorbance of the reaction mixture. Under optimal conditions, the fluorescence increase is linear with tiopronin concentration in the range 5.0-600 ng mL(-1), with a detection limit of 1.5 ng mL(-1) (3sigma). The proposed method has been successfully applied to tiopronin determination in pharmaceutical preparations and in spiked human urine samples.