原位合成纳米金/石墨烯修饰玻碳电极检测水和土壤中痕量铅

摘要

为提高痕量铅的检测精度,提出了一种简单、可控的一步还原法在裸玻碳电极表面原位合成纳米金/石墨烯材料的方法,并通过循环伏安法(cyclic voltammetry,CV)对修饰电极进行电化学表征.利用修饰后的电极对醋酸-醋酸钠缓冲溶液中的铅离子(Pb(Ⅱ))标准样品进行检测,并对检测条件进行了优化.优化条件下的试验结果表明,在pH值为4.5的醋酸-醋酸钠缓冲溶液中,Pb(Ⅱ)的溶出峰为?0.08 V,在1~90μg/L范围内Pb(Ⅱ)的溶出峰电流与Pb(Ⅱ)浓度之间呈现良好的线性关系(R2=0.985),最小检测下限为0.27μg/L.在优化后的条件下采用该电极测定了实际水样与土壤中的Pb(Ⅱ)含量,加标回收率区间分别为93.75%~109.20%和93.82%~109.9%,相对标准偏差均小于7%,可以用于对实际水样与土壤样本的检测.%Lead is a toxic heavy metal which is extremely harmful to the human body. Lead and its compounds can cause great harm to nerves, hematopoiesis, digestion and kidneys. In agricultural production, lead in water and soil can be deposited in crops, which is one of the main causes of lead pollution. Therefore, the detection of lead in water and soil is very important. Recently, it was reported that square wave anodic stripping voltammetry (SWASV) by using different nanomaterials modified working electrode had great test performance in heavy metal ions detection. Compared with the traditional mercury or bismuth film modified electrode, which can have secondary pollution to the environment, nanomaterials modified electrode has lower detection limit and broader detection range, and can be more stable than mercury or bismuth film modified electrodes. In this study, the graphene and HAuCl4 were used to fabricate graphene/gold nanoparticles modified glassy carbon electrode. First, 5μL graphene-DMF(1 g/mL) solution and 153 μL HAuCl4 (48.65 mmol/L) were added into 842 μL ethanol solution (50%). 6 μL suspension of GR/HAuCl4 was casted on a glassy carbon electrode, and kept for drying at room temperature. GR-AuNPs/GCE was electrochemically reduced in the 0.5 mol/L NaCl by cyclic voltammetry method between -1.3 V and +0.8 V at 50 mV/s scan rate for 11 potential cycles. The electrochemical characterization of the GR/AuNPs/GCE was studied by cyclic voltammetry (CV) method. The results showed that the GR-AuNPs/GCE had better surface conductivity compared with the bare GCE and the GR/GCE. The modified electrode was used to detect the standard samples of lead (Ⅱ) in acetate buffer solution by square wave anodic stripping voltammetry with an amplitude of 0.025 V, pulse width of 0.2 s, pulse period of 0.4 s, and scan range between ?1.3 and +0.8 V. The deposition potential was ?1.2 V and the deposition time was 180 s. Before the next cycle, the electrode was cleaned for 60 s at 0.8 V with stirring. For a better detection result, some detection conditions were optimized including the concentration of HAuCl4 in the GR-HAuCl4 mixed liquid, potential cycles of cyclic voltammetry, pH value of the acetate buffer solution, deposition potential and deposition time. Under all optimization conditions, the dissolution peak of lead ion (Ⅱ) is ?0.08 V in acetate buffer solution, and had a linear response to lead ion (Ⅱ) in the concentration range from 1 to 90 μg/L (R2 = 0.985), with the detection limit concentration of 0.27 μg/L. GR-AuNPs/GCE was successfully used to analyze the concentration of lead ion (Ⅱ) in water and soil with standard join law. Water and soil used for this experiment was obtained from Hangzhou Dianzi University, both divided into five groups. Both water samples and soil samples had five concentrations from 10 to 50 μg/L. The recovery ranges of lead ion (Ⅱ) in water samples and soil samples were 93.75%-109.2% and 93.82%-109.92%, with all RSDs were below 7%, which showed that the GR-AuNPs/GCE has a good detection performance for the actual samples.