Sequential Injection Analysis Method for the Determination of Glutathione in Pharmaceuticals

A sequential injection analysis method for the determination of glutathione (GSH) in pharmaceuticals has been developed. It is based on the reduction of the Cu(II)-neocuproine complex by GSH and the formation of an orange-yellow colored Cu(I)-neocuproine complex with maximum absorbance at 458 nm. Under optimal conditions the method is characterized by a linear calibration range of 6.0 × 10^-7-8.0 × 10^-5 mol L^-1 (A = 3270 C - 0.0010; R² = 0.9983), limit of detection of 2.0 × 10^-7 mol L^-1, limit of quantification of 6.7 × 10^-7 mol L^-1, repeatability (expressed as relative standard deviation) of 3.8%, and sampling rate of 60 h^-1. The newly developed method has been successfully applied to the determination of GSH in pharmaceutical samples with no statistically significant difference between the results obtained and those produced by the standard Pharmacopoeia method.