engleski

Flow injection analysis of N-acetyl-L-cysteine based on the reduction of copper(II)-neocuproine reagent

Novel flow-injection spectrophotometric method for the determination of N-acetyl-L-cysteine (NAC) has been developed and validated. N-acetyl-L-cysteine (Acetylcysteine, NAC) is a synthetic aminothiol antioxidant used in medicine as a mucolytic agent and in the management of paracetamol (acetaminophen) poisoning. 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 yellow Cu(I)-neocuproine complex is measured at 458 nm. The three-line manifold with one reaction coil was used. Optimization of manifold parameters and experimental conditions were carried out by means of univariate method. A linear calibration curve is established in a concentration range of 6×10−7 to 4×10−5 mol L−1 NAC with regression equation y = 3.89103 –0, 0015 (R2 = 0.9996) (n = 9) and detection limit of 9.4×10−8. The proposed method is simple, rapid, sensitive and reproducible (RSD 0.9%, n = 100). The Cu(II)-neocuproine reagent is selective oxidant because only the reducing substances with standard (formal) potentials lower than 0.6 V would have the thermodynamic predisposition to interfere in the proposed method. On the other hand, excellent sensitivity of Cu(II)-neocuproine reagent is probably due to the kinetic reasons because the Cu(I)-neocuproine reagent is an immediate product of one-electron reduction of the reagent with NAC. In addition, proposed method is sensitive enough to enable determination of near nanomole amounts of the NAC without expensive instruments with the analytical frequency of 120 h−1. The proposed method can be applied for the determination of NAC in pharmaceutical preparations. Usual excipients and other present active substances in pharmaceuticals do not interfere with the proposed method.

flow injection analysis; NAC

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