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Flow Injection Spectrophotometric Determination of N-acetylcysteine Ethyl Ester Based on the Reduction of Copper(II)-bicinchoninic Acid Complex

A flow injection method of analysis was developed for the determination of a lipophilic cell-permeable cysteine derivative N-Acetylcysteine ethyl ester (NACET). NACET compared to its congener N-acetylcysteine poseses enhanced pharmacokinetic features. Once administered NACET quickly enters the cells where it is transformed to NAC and cysteine. The proposed method is based on a reduction reaction of an apple green Cu(BCA)22+ complex to a purple Cu(BCA)2+-complex by NACET in a phosphate buffer solution. The absorbance of the generated Cu(BCA)2+ complex is measured at 562 nm. Recorded peak height was used as a quantitative variable in the flow injection procedure. The absorbance of the formed Cu(BCA)2+, was recorded as a function of time with a recording frequency of 5 s–1. The linearity of the proposed flow injection method was obtained over the range 2.0×10–6 mol L-1 – 1.0×10–4 mol L–1 NACET, where the limit of detection was 6.6×10–7 mol L-1. Relative standard deviation obtained by measuring ten replicates of 4×10–5 mol L–1 NACET was found to be 0.7 %. Analytical frequency was 72 analysis per hour.

N-Acetylcysteine ethyl ester; Bicinchoninic acid; Flow injection.

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