An ultraviolet spectral and polarographic study of nitrofurantoin, a urinary-tract antibiotic.

Abstract

Nitrofurantoin, a urinary-tract antibiotic, exists in four different forms over the pH range 0–14, corresponding to the divalent cation H3A2+, the monovalent cation H2A+, the neutral species HA and the monovalent anion A–, as investigated by means of ultraviolet spectrophotometry. The compound is polarographically reducible over the whole pH range, the nitro group being reduced to the hydroxylamine group in a 4e process and subsequently the amine being formed in a 2e process at a pH value below 5. The CN—N linkage is reduced by a mechanism involving reductive fission of the N—N bond. The best defined differential pulse polarographic waves for the reduction of the nitro group to hydroxylamine are obtained in the pH range 6–12.Experiments involving spiking of urine have been carried out and a method is suggested for the determination of nitrofurantoin in urine over the concentration range 2–24 µg ml–1.