Extractive spectrophotometric determination of Nb(V) as its complex with 3-hydroxy-2-(2'-furyl)-4-oxo-4H-1-benzopyran

An intense yellow 1:2 (M:L) complex of niobium(V) with 3-hydroxy-2-(2'-furyl)-4-oxo4H- 1-benzopyran (HFB) can be obtained in perchloric acid medium (4 mol L - 1 ). The complex is extractable to dichloromethane and is stable for more than 1 h. Beer's law is obeyed in the Nb(V) concentration range of 0-1.8 pg mL - 1 . Molar absorptivity and Sandell's sensitivity when applying spectrophotometric detection at the wavelength of 415 nm, were 5.2 × 10 4 L mol - 1 cm - 1 and 0.0018 μg cm - 2 , respectively. Relative standard deviation was of the order of 0.3-1.3%. The method is free from interference of several analytically important elements. The proposed method is applicable to the samples of various complexities.