A spectrofluorimetric sequential injection method for the determination of penicillamine using fluorescamine in the presence of β-cyclodextrins

A simple, robust and sensitive sequential injection spectrofluorimetric method for the determination of penicillamine (PA) in pharmaceutical formulations is developed. The method is based on the formation of a highly fluorescent derivative when penicillamine is reacted with fluorescamine (FL) in borate buffer of pH 9.3. The derivative produced is monitored at an emission wavelength of 495 nm using an excitation wavelength of 355 nm. The optimum conditions for the determination of PA with FL were: 3 mM FL, pH 9.3, 5 mM methyl-β-cyclodextrin, sample volume of 75 μL and reagent volume of 75 μL. Furthermore, the effect of various media on the fluorescence intensity of the PA-FL derivative was studied and methyl-β-cyclodextrin was found to give the largest enhancement. A linear dynamic range for the determination of PA of 5-80 ppm was obtained with a sampling frequency of 50 h ^-1 and a relative standard deviation of less than 2.5%. The method was applied to the determination of PA in pharmaceutical formulations with reasonable recoveries ranging from 101.0-103.1%, indicating that no interference is observed from concomitants usually present in dosage forms.