Flow-Injection Lucigenin–Cu(III) Complex Chemiluminescence Determination of Cysteine and Glutathione in Pharmaceutical Formulations

Abstract

A flow injection method for the determination of cysteine (CySH) and glutathione (GSH) amino acids is reported based on lucigenin−diperiodatocuprate(III) complex chemiluminescence (CL) reaction in basic medium. Under optimum conditions, linear calibration curves were obtained in the range of 0.001–30 (R2 = 0.9998, n = 6) and 0.005–30 mg/L (R2 = 0.9989, n = 6) with detection limits (S/N = 3) of 2.5 × 10–4 and 8 × 10–4 mg/L for CySH and GSH, respectively. The relative standard deviation was 4.1% (n = 11) with injection throughput of 160 per hour. We have applied the developed method to determine CySH and GSH in pharmaceutical samples and compared the results with a spectrophotometric method. Statistical tests such as Student’s t- and F-tests were applied for both results with no significant difference observed at a 95% confidence level. The CL reaction of lucigenin−copper(III) complex is also presented.