A titled method has been developed with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol as chromogenic reagent in KHC_8H_4O_4-HCl buffer solution at pH 2. 4. Principal interfering ion Fe(Ⅲ) in crude oil and residual oil was masked with NH_4F(1%). Beer＇s law was obeyed in the range of 0～26μg/25ml for Ni(Ⅱ) and V(Ⅴ). The experimental results agree with those obtained by ICP-AES and AAS.
Chinese Journal of Analytical Chemistry