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钽试剂(N-苯甲酰苯基羟胺)为显色剂的萃取光度法测定钒早有报道,已应用于矿石、钢铁和金属中钒的测定,但应用于石油中钒的测定很少报道。五价钒与钽试剂在约1.5N硫酸介质中生成的沉淀能定量地被氯仿和乙醇混和溶剂所萃取,形成橙黄色的络合物。经实验表明,络合物的最大吸收波长为445nm,可稳定2小时,萃取酸度在0.4～2.5N范围内络合物的吸光度最大且稳定。Fe~(3+)和Ti~(4+)严重干扰,用1毫升磷酸可以隐蔽4毫克Fe~(3+),1毫克Ti~(4+),Ni~(2+),Cu~(2+)不干扰测定,1～5毫升磷酸无影响。钒在2.5～25.0微克/10毫升范围内符合比耳定律。对试样多次分析结果表明,其相对偏差均在10％以下。本法是将试样加热处理酸溶后,直接用钽试剂萃取测定,方法简便快速准确,也适用于原油中钒的测定。
Determination of vanadium by tantalum reagent (N-benzoylphenylhydroxylamine) as chromogenic reagent has been reported for a long time and has been used in the determination of vanadium in ores, steel and metals. However, the determination of vanadium used in petroleum has rarely been reported . Precipitation of pentavalent vanadium and tantalum reagents in about 1.5 N sulfuric acid medium can be quantitatively extracted by a mixed solvent of chloroform and ethanol to form an orange-yellow complex. The experimental results show that the maximum absorption wavelength of the complex is 445nm, can be stable for 2 hours, the absorbance of the complex in the range of 0.4-2.5N is the largest and stable. Fe (3+) and Ti ~ (4+) were seriously disturbed. With 1 ml of phosphoric acid, 4 mg of Fe 3+, 1 mg of Ti 4+, Ni 2+, Cu ~ 2+) does not interfere with the determination of 1 to 5 ml of phosphoric acid no effect. Beer’s law is valid for vanadium in the range of 2.5-25.0 μg / 10 ml. Multiple analysis of the sample results show that the relative deviation of 10% or less. This method is to heat the sample after acid-soluble, direct tantalum reagent extraction determination, the method is simple and quick and accurate, but also for the determination of vanadium in crude oil.