Surfactant‐Mediated Catalytic Determination of Fe(II) in Herbal and Pharmaceutical Products

Abstract

In the present work, the catalyzed oxidation of neutral red (NR) by bromate was used to work out a kinetic-based analytical method as an alternative technique for the determination of Fe(II) in real and synthetic samples. A use of a surfactant, N-dodecylpyridinium chloride enhanced the sensitivity of the reaction by becoming involved in the reaction mechanism and providing a more suitable reaction environment. The iron-catalyzed oxidation of NR with potassium bromate was studied kinetically by using a fixed time method. The reaction was followed by measuring the decrease in absorbance at 535 nm. The use of a surfactant in the analytical run showed a five times increase in the sensitivity of the method. It served as a ready reservoir of NR by increasing its solubilization. The salt effect, pH, and reagent concentration were also investigated to achieve a more selective and sensitive analytical procedure. Under optimized conditions (4.2 · 10 -5 mol L -1 NR, 1.4 · 10 -3 mol L -1 KBrO 3 , 1.5 · 10 -2 mol L -1 cationic surfactant, 0.5 mol L -1 LiCl and pH 2.60 at 30°C), iron(II) was determined in the range 0.1-0.5 lg mL -1 with a detection limit of 0.019 lg mL -1 and a relative standard deviation (n = 6) 1.02% for 0.2 lg mL -1 Fe(II). The influence of foreign ions on the accuracy of the results was investigated. The developed method is extremely sensitive, selective and simple. The method was applied successfully to the determination of iron in the herbal pharmaceutical and synthetic samples. The results showed good agreement with those obtained by atomic absorption spectrophotometry.

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