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Flow-injection Determination of Glutathione, Penicillamine and Tiopronin Based on the Reduction of Copper(II)-neocuproine Reagent

A new flow-injection spectrophotometric method for the determination of glutathione (GSH), penicillamine (PEN) and tiopronin (mercaptopropionyl glycine, MPG) in pharmaceutical formulations is reported. The method is based on the reduction of Cu(II)-neocuproine reagent to Cu(I)-neocuproine by GSH, PEN or MPG in buffered medium (pH = 3) to form a stable coloured complex (λmax = 458 nm). Experimental conditions were optimized by univariate method, resulting with linear calibration curves in concentration range from 2 × 10−6 to 3 × 10−5 mol L−1 for GSH, 6 × 10−7 to 4 × 10−5 mol L−1 for PEN and 4 × 10−7 to 4 × 10−5 mol L−1 for MPG. The achieved analytical frequency was 180 h−1 for GSH and PEN and 120 h−1 for MPG. The proposed method was successfully applied for determination of GSH, PEN and MPG in pharmaceutical formulations, and the usual excipients in pharmaceuticals did not interfere with the analysis.

glutathione ; penicillamine ; tiopronin ; flow-injection analysis ; spectrometric determination ; thiols ; pharmaceuticals.

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