Spectrophotometric determination of N-acetylcysteine in drug formulations with o-phthalaldehyde and isoleucine

Abstract

A spectrophotometric procedure is proposed for the assay of N-acetylcysteine (NAC) in the range 0.5–49 µg ml^–1, based on the reaction of the thiol group with o-phthalaldehyde and isoleucine at pH 9.5 (λ_max.= 335 nm). The procedure was applied successfully to the determination of NAC in several pharmaceutical formulations. The recoveries ranged from 98 to 106%, with relative standard deviations of less than 1.5%. The method is free from interferences and is simple, rapid and easy to automate.