该课题旨在筛选金属结合肽His-Trp-His(HWH),通过电化学法制备电极实现检测Cd2+的目的。通过量子化学模拟的方法计算金属离子(Cd2+、Cr2+、Cu2+、Pb2+、Ni2+、Zn2+)与短肽HWH的结合模式,发现HWH与Cd2+可形成较强的螯合作用,螯合作用的距离分别为2.0、2.1、2.4 Å,结合能为-6.4 kcal/mol。对制备多肽电极的方法进行了考察,发现以滴涂法先富集壳聚糖,再滴加多肽的方式制备出来的多肽复合电极效果最佳。利用该多肽电极对某一特定浓度的Cd2+离子标准溶液进行检测,以控制变量法的原理对电解质pH、富集时间、富集电位逐一进行考察,找出最佳检测条件。最终确定实验的最佳条件为电解质pH 6、富集时间150 s、富集电位-1.1 V,对一系列浓度梯度的Cd2+离子溶液的检测实验证明,在0.001~0.30 mg/L的质量浓度内,Cd2+离子浓度与其溶出峰电流值呈良好的线性关系,线性方程为I (μA)=86.78C (mg/L)+0.171 0,R2=0.998 9。经计算后得到该方法的检测限可达4.301×10-4 mg/L,用该方法对饮用水、大学城湖水以及某饮料进行检测,其加标回收率为97.4%~103.5%,与原子光谱以及电感藕合等离子体质谱法的回收率相近。实验证明多肽电极方法能够实际用于Cd2+离子的检测。
The purpose of this study was to screen His-Trp-His (HWH) and to prepare electrodes for the detection of Cd2+ by electrochemical method. The binding mode of metal ions (Cd2+, Cr2+, Cu2+, Pb2+, Ni2+, and Zn2+) with short peptide HWH was calculated by quantum chemical simulation. It was found that HWH and Cd2+ could form strong chelation, and the chelation distance was 2.0 Å, 2.1 Å, and 2.4 Å, respectively. The binding energy of Cd2+ to HWH was -6.4 kcal/mol. The preparation method of polypeptide electrodes was investigated. It was found that the best effect was obtained by the method of enriching chitosan and then adding polypeptide. The polypeptide electrode was used to detect a specific concentration of Cd2+ ion standard solution, and the electrolyte pH, enrichment time, and enrichment potential were investigated one by one by the principle of control variable method to find out the best detection conditions. Finally, the optimal conditions of the experiment were determined as the electrolyte of pH 6, enrichment time of 150 s, and enrichment potential of -1.1 V. A series of Cd2+ ionic solutions with concentration gradients showed that in the concentration range of 0.001-0.30 mg/L, the linear equation was I (μA)=86.78C (mg/L)+0.171 0, R2=0.998 9. After calculation, the detection limit of this method could reach 4.301×10-4 mg/L. The recovery rate of this method was 97.4%-103.5% for drinking water, lake water of a university city, and a certain beverage, which was similar to that of the atomic spectrum and inductively coupled plasma mass spectrometry. The experiment shows that the polypeptide electrode method can be used for the detection of Cd2+ ions.
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