催化动力学褪色光度法测定痕量钒

Determination of trace Vanadium(Ⅴ) by catalytic kinetics discoloring spectrophotometric

研究了在H3PO4介质中,钒(V)对KBrO3氧化偶氮氯磷mA褪色反应的催化作用及柠檬酸的活化作用,建立了测定钒的新方法.实验发现,无柠檬酸时体系为准零级反应,表观活化能为54.3 KJ/mol.在柠檬酸存在下则为准一级反应,表观活化能为30.9kJ/mol,钒的量在0～5.0×10-8g/mL范围内与1og(A0/A)呈线性,检出限为5.6×10-11g/mL.在NH4F及尿素存在下,大多数常见离子无干扰.可用于钢样中微量钒的直接测定.

Based on the catalytic effects of vanadium （V） on the discoloring reaction of chlorophos-phonazo mA oxidized by KBrO3 and activation effect of citric acid in a medium of phosphoric acid, a new method for the determination of vanadium was proposed. The experimental results indicate that the system is quasi-zero-order reaction without citric acid. The apparent activation energy is 54.3 kJ/mol. In the presence of citric acid, the system is a quasi-one-order reaction. The apparent acti- vation energy is 30.9 kJ/mol. Linear relationship between log（Ao/A） and the concentration of vanadium is observed in the range of 0- 5.0 ×10^-8 g/mL. The limit of detection is 5.6 ×10^-11 g/mL. In the presence of NH4F and urea, most of the common ions did not interfere with the determination of vanadium. It is applied to the direct determination of trace vanadium in steel samples.