离子交换树脂分离富集-催化荧光猝灭法测定痕量钒

Determination of trace vanadium by catalytic fluorescence quenching method after separation and preconcentration by ion exchange resin

在pH5．2的邻苯二甲酸氢钾一氢氧化钠介质中，痕量钒对高碘酸钾氧化3-（4，-甲基苯基）-5-（4′-甲基-2′-磺酸基苯偶氮）若丹宁（M4MRASP）产生荧光猝灭作用，且猝灭程度与钒量成正比，由此建立了催化荧光猝灭法测定痕量钒的新方法。该体系最大激发和发射波长为λex=309nm，λem=407nm，测定了反应表观活化能为39．24kJ／mol，反应速率常数为0．274／s。方法测定钒的线性范围为0．15～14．0μg／L，检出限为8．9×10^-8g／L。采用强碱性阴离子交换树脂分离富集，在pH7．0～8．2的范围内能定量吸附钒，交换后的树脂用1．0mol／L硫酸淋洗即可以把钒洗脱，消除了共存离子的干扰。用于实际样品中痕量钒的测定，RSD≤3．1％，标准加入回收率在98．3％～103．4％之间；测定结果与ICP-AES法结果基本一致。

On the basis of the catalytic effect of vanadium on oxidation of 3-（4′-methylphenyl）-5- （4′- methyl-2′-sulfonylphenylazo） rhodanine by potassium periodate in potassium hydrogen phthalate-sodium hydroxide （pH 5.2） ,a new catalytic fluorescence quenching method for determination of trace vanadium was investigated. The maximum excitation wavelength and emission wavelength of the system was at 309 nm and 407 nm. The apparent activation energy was 39.24 kJ/mol and the reaction rate constant was 0. 274 /s. Under the optimum conditions, the decrease of fluorescence intensity had a linear relationship against the concentration of vanadium in the range of 0.15-14.0μg/L. The detection limit was 8. 9 × 10^-8 g/L. At pH 7.0- 8.2, vanadium was separated and enriched by anion exchange resin. Then the resin was eluted by 1.0 mol/L H2SO4, which greatly improved the selectivity and sensibility of the system. The method was successfully used to determine trace amounts of vanadium in real samples with the RSD less than 3.1 % and the recovery between 98.3 % and 103.4 %. The results obtained by this method are in good agreement with those obtained by ICP-AES.