Application of highly selective and sensitive 6-chloro-3-hydroxy-2-(2'-furyl)-4-oxo-4H-1-benzopyran reagent for spectrophotometric determination of tungsten(VI)

A simple, fast, and highly selective method for spectrophotometric determination of trace tungsten has been presented. In the determination 6-chloro-3-hydroxy-2-(2'-furyl)-4-oxo--4H-1-benzopyran (CHFB) has been applied as a ligand to complex the analyte metal ion. The formed light-yellow complex was extracted into dichloromethane from 0.2 mol L -1 HCl solution. The Beer's law was obeyed in the concentration range of W(VI) of 0.0-2.0 μg mL -1 ; molar absorptivity and Sandell's sensitivity of the complex at 420 nm equaled 2.2 x 10 4 L mol -1 cm -1 and 0.0083 μg W(VI) cm -2 , respectively. The method is free from the interference of many analytically important elements. The proposed system handles satisfactorily the analysis of several samples of various complexity. The obtained results were highly reproducible with a relative standard deviation of 0.08% for 10 μg of W(VI) per 10 mL of the aqueous volume.