Flow injection kinetic spectrophotometric determination of trace amounts of Se(IV) in seawater

A simple, accurate, sensitive and selective flow injection catalytic kinetic spectrophotometric method for rapid determination of trace amounts of selenium is proposed in this paper. The proposed method is based on the accelerating effect of Se(IV) on the reaction of ethexlenediamine tetrecetic acid disodium salt (EDTA) and sodium nitrate with ammonium iron(II) sulfate hexahydrate in acidic media. The absorbance intensity was registered in this reaction solution at 440 nm. The calibration graph is linear in the range of 5 × 10−9–2 × 10−7 and 2 × 10−7–2 × 10−6 g ml−1. The detection limit is 2 × 10−9 g ml−1. The relative standard deviation was 3.4% for 5 × 10−8 g ml−1 Se(IV) (n = 11), 2.7% for 5 × 10−7 g ml−1 Se(IV) (n = 11). This method is very simple, rapid and suitable for automatic and continuous analysis. The presented system has been applied successfully to determination of Se(IV) of seawater samples.