STUDY ON THE DOUBLE-PEAK-DOUBLE WAVELENGTH SPECTROPHOTOMETRY OF THE COLOUR REACTION BETWEEN ALUMINUM AND PYROCATECHOL VIOLET

In a hexamine-HCl buffer solution of pH 6.0～6.3, a stable complex is formed between pyrocatechol violet (PCV) and Al(Ⅲ) in the presence of CTMAB, exhibiting an absorption peak at 580nm and a negative absorption peak at 448nm. Based on this phenomenon, a method of determination of aluminum(Ⅲ) by DW-spectrophotometry using 580nm as λ_1 and 448nm as λ_2. Beer′s law is kept between ΔA(A_(580)-A_(448)) and concentration of Al(Ⅲ) in the range 0 to 6μg per 25ml of color solution. Molar absorptivity of the DW-spectrophotometric method is found to attain a value of 9.51×10~4L·mol~(-1)·cm~(-1) which is about 66% higher than the value of e (5.73×10~4L·mol~(-1)·cm~(-1)) found by the conventional spectrophotometry. In its application to the analysis of bush feed samples, consistent results were obtained in checking with the CAS photometric method, and the recoveries obtained were in the range 96.0%～106.0%.