碘-淀粉络合物褪色光度法测定微量氰化物

PHOTOMETRIC DETERMINATION OF CYANIDE BY ITS DECOLORATION REACTION WITH THE BLUE COMPLEX OF IODINE AND STARCH

研究了在 p H 7.0的混合磷酸盐缓冲溶液条件下 ,氰根使碘与淀粉形成的蓝色络合物褪色 ,络合物吸光度的降低值 ΔA与加入的氰根量成正比。 λmax=570 nm,氰根在 0～ 2 0 μg/2 5ml范围内呈良好的线性关系 ,检出限为 0 .52μg/2 5ml,其表观摩尔吸光系数为 2 .6× 1 0 4 ,方法成功地用于含氰废水中氰化物的测定。

A decolorizing effect of the blue complex formed between iodine and starch is observed when it is reacted with cyanide ion. Based on this phenomenon, an indirect photometric method for the determination of CN - ion is proposed in this paper. The decoloration reaction is carried out in a Na 2HPO 4 KH 2PO 4 buffer medium of pH 7.0. The decrease in absorbance is measured at 570nm which is the absorption maxima of the blue complex. A linear relationship is found between the decrease of absorbance (Δ A ) and the CN - concentration in the range 0~20μg per 25ml with an apparent molar absorptivity of 2.6×10 4L·mol -1 ·cm -1 . The detection limit is 0.52μg/25ml. The proposed method has been satisfactorily applied to the determination of CN - in waste water.