Flow-injection spectrophotometric determination of ascorbic acid in pharmaceutical products with the Prussian Blue reaction

被引:52
作者
Nobrega, JA
Lopes, GS
机构
[1] Grupo de Quim. Analítica, Departamento de Química, Univ. Federal de São Carlos, CEP 13565-905, São Carlos, SP
基金
巴西圣保罗研究基金会;
关键词
ascorbic acid; flow-injection analysis; iron; pharmaceuticals; Prussian Blue reaction;
D O I
10.1016/0039-9140(95)01830-1
中图分类号
O65 [分析化学];
学科分类号
070302 ; 081704 ;
摘要
A lot of modern analytical strategies for exploiting chemistries have been developed by using flow-injection analysis. However, even after 20 years of flow-injection evolution, there still are new quantitative procedures being established using old qualitative assays. The formation of Prussian Blue is a classical test to detect Fe2+ using hexacyanoferrate(III) as a precipitating reagent. This reaction was evaluated for spectrophotometric determination of ascorbic acid employing Fe3+ and hexacyanoferrate(III) as chromogenic reagents. An excess of the complexing anion avoids the formation of precipitate and forms a deep blue solution when Fe3+ is reduced to Fe2+ by ascorbic acid. The maximum absorbance of the colored complex occurs at 700 nm and the molar absorptivity is 3.0 x 10(4) 1 mol(-1) cm(-1). Under flow-injection conditions the Prussian Blue reaction was employed with an intermittent flow of an oxalate alkaline solution for removing the colored product adsorbed on tube and flow-cell walls. Reference solutions containing 5.0 x 10(-6)-1.0 x 10(-4) M of ascorbic acid were employed to obtain the analytical curve (r = 0.9999). For all solutions the relative standard deviation was lower than 1.0%, (n = 10). Results obtained for ascorbic acid determination in pharmaceutical products (Cewin, Redoxon and Cebion) are in good agreement with those obtained by using a flow-injection procedure involving the reaction between triiodide and ascorbic acid. The sampling frequency is 140 h(-1) and only 430 mu l of reagents is consumed in each determination.
引用
收藏
页码:971 / 976
页数:6
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