¹Department of Chemistry, GLA University, Mathura, 281006, U.P., India
²Department of Chemistry, B. N College of Engineering & Technology, Lucknow, U.P., India
³Department of Chemistry, DDU Gorakhpur University, Gorakhpur, 273001, UP (India)
⁴Bio-Analytical Division, Shriram Institute for Industrial Research, 19-University Road, 110007-Delhi, India DOI : 10.29228/jrp.312 A simple, reproducible, and rapid kinetic method for the S-Carboxymethyl-L-cysteine (CCys) determination has been proposed and linked to CCys quantification in pharmaceutical preparations. The method is based on the inhibitory feature of Carbocisteine. CCys 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 ionic strength (I) = 0.1 mol dm^-3 (KCl), [Pyrazine (Pz)] = 3.0 × 10^-4 mol dm^-3, pH = 4.0 ± 0.03, [Hg⁺²] = 1.5 × 10^-4 mol dm-3, [Ru(CN)64-] = 2.75 × 10^-5 mol dm^-3, and at 45.0 ± 0.2 º C temperature, fixed time of 9 and 14 min was selected to compute the absorbance at 370 nm corresponding to the ultimate reaction product [Fe(CN)5 Pz]3-. With the proposed kinetic spectrophotometric method, the micro-level quantification of CCys in distinct water samples can be done down to 1.25 × 10^-6 mol dm^-3. The developed procedure is highly reproducible and can be efficiently used to quantitatively estimate the CCys in the drug samples with high accuracy. The general additives present in drugs do not substantially interfere in the determination of CCys even up to 1000 times with [CCys]. Keywords : Hexacyanoruthenate(II); Excipients; Catalyst inhibitor complex; Ligand substitution reaction; Inhibitory effect, Carbocisteine