¹Department of Chemistry, GLA University, Mathura- 281406, U.P., India
²Department of Chemistry, M.J.S. Government P.G. College, Bhind, M.P., India
³Department of Chemistry, Dr. Shakuntala Misra National Rehabilitation University, Lucknow, U.P., India
⁴Department of Chemistry, Shri Ramswaroop Memorial University, Barabanki, 222502, U.P., India DOI : 10.29228/jrp.262 A 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 Hg²⁺ and reduces the actual Hg²⁺ concentration and ultimately the rate of reaction between pyrazine (Pz) and [Ru(CN)6]4- catalyzed by Hg2+. Under the optimized reaction conditions with [Ru(CN)6⁴-] = 7.25 × 10^-5 mole dm^-3, I = 0.1 mole dm^-3 (KCl), Temp = 45.0 ± 0.1 o C, [Hg⁺²] = 1.5 × 10^-4 mole dm^-3, [Pyrazine] = 8.5 × 10^-4 mole dm^-3, and pH = 4.0 ± 0.02, fixed time of 12 and 17 min was selected to compute the absorbance at 370 nm corresponding to the ultimate reaction product [Ru(CN)5 Pz]^3-. The inhibitory action of NAC towards cyanide imitation by pyrazine from [Ru(CN)6]^4-, catalyzed by Hg²⁺ 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 1.5 × 10^-6 mole 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]. Keywords : Hexacyanoruthenate(II); pharmaceutical preparations; excipients; catalyst inhibitor complex; Nacetylcysteine; ligand substitution reaction; inhibitory effect