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8157540 
Journal Article 
Extractive spectrophotometric determination of tungsten(VI) using 3-hydroxy-2-(2′-furyl)-4-oxo-4H-1-benzopyran as a complexing agent 
Agnihotri, N; Mehta, JR 
2004 
Yes 
Journal of the Indian Chemical Society
ISSN: 0019-4522 
81 
8 
713-716 
English 
An extractive spectrophotometric method is developed for the trace determination or tungsten. Tungsten(VI) forms a light yellow (1:2) complex with 3-hydroxy-2-(2′-furyl)-4-oxo-4H-1-benzopyran (HFB) in acidic medium. The coloured species is quantitatively extracted into dichloromethane and absorbance is measured at 405-413 nm. The method obeys Beer's law in the range 0-2.3 μg WVI ml-1 with molar absorptivity and Sandell's sensitivity of 4.88 × 104 dm3 mol-1 cm-1 and 0.0038 μg W cm-2, respectively, at 410 nm. The method is free from the interference of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Nb, Ta, Mo, U, Zr, Th, Ce, Se, Re, platinum metals and many other analytically important elements. The proposed system handles satisfactorily the analysis of several samples of varying complexity.