A sensitive and selective extractive spectrophotometric determination of tungsten(VI) using 6-chloro-3-hydroxy-2-( 4' -methoxyphenyl)-4-oxo-4H-1- benzopyran

Department of Chemistry, Kurukshetra University. Kurukshetra-136 119, Haryana, India E-mail : search@v idya. kuk. ernet. in; search@granth. kuk. ernet. in Fax : 91-1744-238277, 238628 Manuscript received 6 December 2004, revised 16 September 2005, accepted 2 December 2005 A simple, rapid, sensitive and selective spectrophotometric method for the determination of tungstwen(VI) in trace amounts is developed using 6-chloro-3-hydroxy-2-(4'-methoxyphcnyl)-4-oxo-4H-1·benzopyran (CHMPB) as a reagent for the complexation of metal ion and extracting the 1 : 2 (metal : ligand) complex into dichloromethaue from 0.2 M HCI solution. It obeys Beer's law in the range 0-2.1 )μg WVI ml-1 with molar absorptivity and Sandell's sensitivity at 415 nm as 6.08 x 104 dm3 mol-1 cm-1 and 0.00302 )μg W cm-2, respectively. The method is free from the interference of a large number of elements (40) and has been applied for the determination of tungsten in a variety of samples with satisfactory accuracy.