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.
Published Version
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