Flow-Injection Spectrophotometric Determination of N-acetylcysteine in Pharmaceutical Formulations with On-Line Solid-Phase Reactor Containing Zn(II) Phosphate Immobilized in a Polyester Resin

Author： Suarez Willian Toito Madi Alexandro Alves Vicentini Fernando Campanhã Fatibello-Filho Orlando

Publisher： Taylor & Francis Ltd

ISSN： 0003-2719

Source： Analytical Letters, Vol.40, Iss.18, 2007-12, pp. : 3417-3429

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Abstract

A flow-injection spectrophotometric procedure was developed for determining N-acetylcysteine in pharmaceutical formulations. The sample was dissolved in deionized water and 400 µl of the solution was injected into a carrier stream of 1.0×10-2 mol l-1 sodium borate solution. The sample flowed through a column (70 mm length×2.0 mm i.d.) packed with Zn3(PO4)2 immobilized in a polymeric matrix of polyester resin and Zn(II) ions were released from the solid-phase reactor because of the formation of the Zn(II) (N-acetylcysteine)2 complex. The mixture merged with a stream of borate buffer solution (pH 9.0) containing 5.0×10-4 mol l-1 Alizarin red S and the Zn(II)Alizarin red complex formed was measured spectrophotometrically at 540 nm. The analytical curve was linear in the N-acetylcysteine concentration range from 3.0×10-5 to 1.5×10-4 mol l-1 (4.9 to 24.5 µg ml-1) with a detections limit of 8.0×10-6 mol l-1 (1.3 µg ml-1). The relative standard deviations (RSDs) were smaller than 0.5% (n=10) for solutions containing 5.0×10-5 mol l-1 (8.0 µg ml-1) and 8.0×10-5 mol l-1 (13.0 µg ml-1) of N-acetylcysteine, and the analytical frequency was 60 determinations per hour. A paired t-test showed that all results obtained for N-acetylcysteine in commercial formulations using the proposed flow-injection procedure and a comparative procedure agreed at the 95% confidence level.