Inhibitory Kinetic Approach for the Rapid Micro-Level Quantification of N-Acetylcysteine

simple, reproducible, and rapid kinetic method for the N-acetylcysteine (NAC) determination has been proposed and linked to NAC quantification in pharmaceutical preparations. The method is based on the inhibitory feature of N-acetylcysteine. NAC forms a stable complex with Hg 2+ and reduces the actual Hg 2+ concentration and ultimately the rate of reaction between 2.2'-bipyridine (Bipy) and [Fe(CN) 6 ] 4– catalyzed by Hg 2+ . Under the optimized reaction conditions with I = 0.1 mol dm –3 (KNO 3 ), [Bipy] = 3.0 × 10 –4 mol dm –3 , T = 25.0 ± 0.2°C, pH 3.8 ± 0.03, [Hg 2+ ] = 1.0 × 10 –5 mol dm –3 , and [Fe(CN) _6^4 - ] = 4.0 × 10 –3 mol dm –3 , fixed time of 10 and 15 min was selected to compute the absorbance at 400 nm corresponding to the ultimate reaction product [Fe(CN) 5 Bipy] 3– . The inhibitory action of NAC towards cyanide imitation by Bipy from [Fe(CN) 6 ] 4− , catalyzed by Hg 2+ has been demonstrated by a redesigned mechanistic scheme. With the proposed kinetic spectrophotometric method the micro-level quantification of NAC in distinct water samples can be done down to 2.5 × 10 –6 mol dm –3 . The developed procedure is highly reproducible and can be efficiently used to quantitatively estimate the NAC in the drug samples with high accuracy. The general additives present in drugs do not substantially interfere in the determination of NAC even up to 1000 times with [NAC].