STUDY ON THE ABSORPTIOPHOTOMETRIC DETERMINATION OF NIOBIUM BY THE REACTION SYSTEM OF Nb(Ⅴ)-MORIN-TWEEN-80

A method of spectrophotometric determination of trace amounts of Nb was described.A ternary complex of Nb(Ⅴ) with 3,5,7,2′,4′-pentahydroxyflavone (morin) and Tween 80 was formed in HCl medium.Beer′s law was obeyed in range of Nb(Ⅴ) concentration of 0-0.40 mg·L-1 with a correlation coefficient of 0.998 8.Molar absorptivity of the complex was 7.90×104L·mol-1·cm-1 at λmax 430 nm.After separation of interfering Fe(Ⅲ),Al(Ⅲ),V(Ⅴ),W(Ⅶ),Cr(Ⅵ) and Mn(Ⅱ) by precipitation with tannin,Nb was successfully determined in complicated geological samples and alloy samples,with RSD≤4.0% (n=8).