Kinetic Spectrophotometric Determination of N-acetyl-L-cysteine Based on the Reduction of Copper(II)-neocuproine Reagent

Lea Kukoc-Modun,Maja Biocic,Njegomir Radić

doi:10.5562/cca2161

Abstract

A novel simple kinetic spectrophotometric method for the determination of N-acetyl-L-cysteine (NAC) has been developed and validated. The proposed method is based on the reduction of Cu II - neocuproine reagent to Cu I -neocuproine with the analyte, in a Britton-Robinson buffer solution (pH = 3.0). The non-steady state absorbance of the formed Cu I -neocuproine complex is measured at 458 nm. The initial rate and fixed time (at 1 min) methods were utilized for constructing the calibration graphs. The calibration curves for both methods were linear in concentration range from 6.0  10 -7 to 8.0  10 -5 mol L -1 with the limit of detection 1.7  10 -7 mol L -1 . The slope of the initial method calibration curve (1.0181) confirmed the first order reaction. Both proposed methods were successfully applied for the de- termination of NAC in its commercial pharmaceutical formulations. (doi: 10.5562/cca2161)

Highlights

N-acetyl-L-cysteine is a synthetic aminothiol antioxidant used in medicine as a mucolytic agent with the aim of reducing the viscosity of pulmonary secretions in a variety of respiratory illness
The proposed method is based on the redox reaction (Equation (1)) in which NAC (RSH compound) reduces CuII-neocuproine complex to orange-yellow CuI-neocuproine complex:[27]
The spectrum of CuI-neocuproine complex and CuII-neocuproine complex are shown in the Figure 1 curve (a) and (b), respectively

Summary

Introduction

N-acetyl-L-cysteine (acetylcysteine, NAC) is a synthetic aminothiol antioxidant used in medicine as a mucolytic agent with the aim of reducing the viscosity of pulmonary secretions in a variety of respiratory illness. The European Pharmacopeia recommended iodimetric titration for pharmaceutical formulations analysis.[2] Other reported methods described in the literature comprise: titrimetry,[3,4] spectrophotometry,[5,6,7,8,9] fluorimetry,[10,11,12] chromatography,[13,14] potentiometry,[15] conductometry[16] and voltametry[17,18,19] for the determination of NAC in pure form, in dosage forms and in biological samples These methods are not sufficiently sensitive and selective, or some of them require expensive instrumentation and are too expensive for routine analysis Other reported methods described in the literature comprise: titrimetry,[3,4] spectrophotometry,[5,6,7,8,9] fluorimetry,[10,11,12] chromatography,[13,14] potentiometry,[15] conductometry[16] and voltametry[17,18,19] for the determination of NAC in pure form, in dosage forms and in biological samples.

Methods

Results

Conclusion