Reverse flow injection spectrophotometric determination of iron(III) using chlortetracycline reagent

A simple reversed flow injection colourimetric procedure for determining iron(III) was proposed. It is based on the reaction between iron(III) with chlortetracycline, resulting in an intense yellow complex with a suitable absorption at 435 nm. A 200 mu l chlortetracycline reagent solution was injected into the phosphate buffer stream (flow rate 2.0 ml min(-1)) which was then merged with iron(III) standard or sample in dilute nitric acid stream (flow rate 1.5 ml min(-1)). Optimum conditions for determining iron(III) were investigated by univariate method. Under the optimum conditions, a linear calibration graph was obtained over the range 0.5-20.0 mu g ml(-1). The detection limit (3 sigma) and the quantification limit (10 sigma) were 0.10 and 0.82 mu g ml(-1), respectively. The relatives standard deviation of the proposed method calculated from 12 replicate injections of 2.0 and 10.0 mu g ml(-1) iron(III) were 0.43 and 0.59%, respectively. The sample throughput was 60 h(-1). The proposed method has been satisfactorily applied to the determination of iron(III) in natural waters. (c) 2007 Elsevier B.V. All rights reserved.