酶催化分光荧光法测定环境水中痕量铬(Ⅵ)

铬（Ⅳ）对血红蛋白模拟酶催化荧光体系具有强烈的猝灭作用, 据此建立了一种酶催化分光荧光法测定铬（Ⅳ）的新方法。研究了溶液酸度、L-酪氨酸浓度、血红蛋白浓度、H₂O₂浓度及反应时间等因素对体系的影响。在pH10.4的NH₃·H₂O-NH₄Cl缓冲溶液中, 当L-酪氨酸、血红蛋白和H₂O₂的浓度分别为1.4×10^-4mol/L、1.0×10^-6mol/L和3.5×10^-5mol/L时, 测定铬（Ⅳ）的线性范围为2.0×10^-6～1.0×10^-4mol/L, 检出限为1.1×10^-8mol/L。1000倍NO₃^-、SO₄^2-、Na⁺、K⁺、Cl^-、Br^-, 300倍PO₄^3-、Al³⁺、NH₄⁺, 50倍Mn²⁺、Mg²⁺、Fe²⁺、Cu²⁺, 1倍Fe³⁺对铬（Ⅳ）的测定没有干扰。干扰较大的Fe³⁺, 可加入过量的柠檬酸掩蔽。对浓度为4.8×10^-5mol/L的铬（Ⅳ）进行11次平行测定, 其相对标准偏差为2.8%。该法已成功地应用于环境水样中铬（Ⅳ）含量的测定。

Determination of trace chromium in environmental water by enzymatic catalytic spectrofluorimetry

According to strong quenching effect of chromium on the catalytic fluorescence system of hemoglobin analog enzyme, a novel enzymatic catalytic spectrofluorimetry for determining chromium was established. The influence of acidity, L-tyrosine concentration, hemoglobin concentration, H₂O₂ concentration and reaction time on the system was studied. In NH₃·H₂O-NH₄Cl buffer solution of pH 10.4 and the presence of 1.4×10^-4 mol/L L-tyrosine, 1.0×10^-6 mol/L hemoglobin and 3.5×10^-5 H₂O₂, the linear range for the determination of chromium was 2.0×10^-6-1.0×10^-4 mol/L and the detection limit was 1.1×10^-8 mol/L. 1000 times of NO₃^-, SO₄^2-, Na⁺, K⁺, Cl^- and Br^-, 300 times of PO₄^3-, Al³⁺, NH₄⁺ and 50 times of Mn²⁺, Mg²⁺, Fe²⁺, Cu²⁺ and 1 time of Fe³⁺ did not interfere in the determination of chromium. Fe³⁺ which had more interference could be masked by adding an over dose of citric acid. The RSD was 2.8% for 11 parallel determination of 4.8×10^-5 mol/L chromium,. The method was successfully applied for determining chromium in the environment water.