Abstract. A flow-injection spectrophotometric method is developed for determination of N-acetyl-Lcysteine (NAC) in pharmaceutical formulations. The method is based on coupled redox-complexation reaction, the first step of which is the reduction of Fe III by NAC; the second one includes the complexation of Fe . The analytical frequency was 60 h -1 . Usual excipients used as additives in pharmaceuticals do not interfere with the analysis of NAC. The proposed method is simple, rapid, sensitive, accurate and precise (repeatability RSD 0.29 %, n = 10), and can be applied for determination of NAC in pharmaceutical formulations up to nanomole quantity. (doi: 10.5562/cca1753)
N-acetyl-L-cysteine (NAC), a sulfhydryl-containing compound, is mainly used as a mucolytic and as an antidote for acetaminophen overdose. Flow injection and sequential injection systems were designed and optimized with the aim of providing precise, accurate and reliable flow methods for NAC determination in pharmaceuticals with very low sample and reagent consumption. Proposed methods are based on a redox reaction wherein NAC reduces a complex of Cu(II) and bathocuproine disulfonate (BCS) to orange [Cu(BCS)2]3– complex, which absorption was measured at λmax = 483 nm. The optimized FIA and SIA configuration yielded a linear calibration curve with correlation coefficients (R2 = 0.9999 and R2 = 0.9996) in the concentration range of 3.0 × 10–7 – 3.0 × 10–5 mol L–1 and analytical frequency of 120 h–1 for the FIA method and 4.0 × 10–7 – 4.0 × 10–5 mol L–1, at sampling rate 60 h–1 for the SIA method. The proposed flow methods were successfully applied for the determination of NAC in pharmaceutical products, as the results showed good agreement with the standard method prescribed by Pharmacopoeia. Recoveries were in the range from 98.4% to 101.9% for the FIA method and from 97.2% to 101.8% for the SIA method.
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