Sequential injection lab-on-valve simultaneous spectrophotometric determination of trace amounts of copper and iron

A sequential injection (SI) method in a lab-on-valve (LOV) formal for simultaneous spectrophotometric determination of copper and iron has been devised. The detection chemistry is based oil the complex formation of 2-(5-brono-2-pyridylazo)-5-[N-(3-propyl-N-(3-sulfopropyl)amino]aniline (5-Br-PSAA) with copper(II) and/or iron(II) at pH 4.6. Copper(II) reacts with 5-Br-PSAA to form the complex which has all absorption maximum at 580 nm but iron(III) does not react. In the presence of a reducing agent only iron(II)-5-Br-PSAA complex is formed and detected at 558 run. Under the optimum experimental conditions, the determinable ranges are 0.1-2 mg l(-1) for copper and 0.1-5 mg l(-1) for iron, respectively, with a sampling rate of 18 h(-1). The limits of detection are 50 mu g l(-1) for copper and 25 mu g l(-1) for iron. The relative standard deviations (n = 15) are 2% for 0.5 mg l(-1) copper and 1.8% for 0.5 mg l(-1) iron when determined in standard solutions. The recoveries range between 96 and 105% when determining 0.25-2 mg l(-1) of copper and 0.2-5 mg l(-1) of iron ill artificial mixtures at copper/iron ratios of 1: 10 to 5: 1. The proposed SI-LOV method is Successfully applied to the Simultaneous determination of copper and iron ill multi-element standard solution and in industrial wastewater samples. (c) 2005 Elsevier B.V. All rights reserved.