特定序列的DNA与Cu2+相互作用可形成具有类过氧化物酶活性的DNA-Cu(II)复合物,此复合物的类过氧化物酶活性可以明显加快3,3′,5,5′-四甲基联苯胺与H2O2的反应速率,使溶液颜色由无色变为蓝色。基于此特性,采用干法灰化法对粮食样品进行预处理,建立了粮食中铜的比色检测方法。结果表明,铜标准曲线在0 ~1.0 μg/mL呈二次函数关系,相关系数R2=0.998,检出限为0.01 μg/mL。测定4种粮食类有证标准物质,偏差在-9.2%~+8.2%,变异系数范围为3.93%~6.32%。使用该方法和原子吸收光谱法同时检测10种阳性粮食样品,测量结果无显著差异。该方法简单易行、结果准确,适用于粮食中铜的检测。
DNA-Cu(II) complex with peroxidase-like activity was formed through coordination reactions of Cu2+ with specific DNA sequence.Because of the peroxidase-like activity,this complex could accelerate the reaction rate of 3,3′,5,5′-tetramethylbenzidine-H2O2 and led to a distinct color change of the solution from colorless to blue.On this basis,a colorimetric method was developed for the detection of Cu2+ in grain while the samples were pretreated by dry ashing method.Good quadric relationship was revealed for the standard curve in the range of 0-1.0 μg/mL with a correlation coefficientR2 of 0.998 and a detection limit of 0.01 μg/mL.The determination of four certified reference samples showed that the deviation was -9.2% to +8.2% and coefficient of variation ranged from 3.93% to 6.32%.Ten positive grain samples were determined by both this colorimetric method and flame atomic absorption spectrophotometry,no significant difference was found in the detection results.This method was simple and accurate,which was suitable for the determination of copper in grain.
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