Flow Injection Spectrophotometric Determination of N-Acetylcysteine and Captopril Employing Prussian Blue Generation Reaction

Abstract

A novel flow injection procedure to determine N-acetylcysteine and captopril in pharmaceutical formulations is proposed. The flow procedure developed was based on oxidation of the analytes by Fe(III) in acidic medium and subsequent reaction of the Fe(II) generated with excess hexacyanoferrate(III) to produce soluble Prussian blue (KFe[Fe(CN)₆]) measured at 700 nm. Detection limits of 1.0 × 10⁻⁵ mol L⁻¹ and 3.0 × 10⁻⁵ mol L⁻¹ for N-acetylcysteine and captopril, respectively, were found. The sample throughput was 70 h⁻¹ for both analytes and the results obtained were in agreement at a 95% confidence level with those obtained using reference methods.

Keywords:

• Captopril
• Flow injection analysis
• N-acetylcysteine
• Prussian blue
• Spectrophotometry

Acknowledgments

Authors are grateful to The National Council for Scientific and Technological Development (CNPq), Coordination for the Improvement of Higher Education Personnel (CAPES), São Paulo State Research Foundation (FAPESP) for financial support (2008/11151-1 and 2008/09893-0), and the Bioanalytical – National Institute of Science and Technology-(Bioanalytical-INCT).

Notes

^a Concentration suggested by Nobrega and Lopes (1996).

Mean ± standard deviation; 95% confidence level; E_r = relative error of proposed procedure vs. comparative methods.

^a t _calculated = 2.26.

^b t _calculated = 1.61.

^c Liquid formulation: mg/mL. The analyzed samples contained some inactive ingredients: food yellow 3, orange flavoring, orange essence, talc, and colloidal silicon dioxide.