金电极循环伏安法检测生乳尿素掺杂

通过循环伏安法测定尿素及其掺入生乳中的电化学特性,分析电极界面信息表征。结果表明:当扫描速率为1~25 mV/s时,纯尿素溶液的响应特征为单峰,且峰电位随扫速增大而负移,峰电流值与ν^1/2呈线性关系(I_pc=5.7410ν^1/2-0.07706,r=0.99784;I_pc=18.9488ν^1/2-1.1299,r=0.99086),其电极过程为不可逆过程,经计算可得其反应电子数和质子数均为1,交换系数α为0.558,电化学速率常数k_s为0.43207±0.0001 s^-1。在生乳中掺尿素后,将三氯乙酸加入掺杂乳混匀,再离心除去脂肪和蛋白质得清澈液,经检测清澈液可知,当掺杂尿素浓度为0.3~2.5 mol/L时,其浓度与峰电流值呈线性关系(I_pc=7.7847+3.3098C/(mol/L),r=0.9945)。该方法对尿素的检出限为0.171 mol/L,与其他测定方法相比,此法样品预处理简单、测定速度快、成本低,能较好的运用于实际生产线。

Detection for urea in raw milk on a gold electrode through cyclic voltammetry

Through Cyclic Voltammetry, electrochemical characteristics of urea and its mixture with raw milk were detected, and the electrode interface information was analyzed. The results showed that, when the scanning rate was 1~25 mV/s, the response characteristic of pure urea solution was a single peak, and the peak potential decreased linearly with the increasing of scanning rate. The peak current value was linear with ν1/2(I_pc=5.7410ν1/2-0.07706, r=0.99784;I_pc=18.9488ν1/2-1.1299, r=0.99086). The electrode process was irreversible. After calculation, the reaction's electron number and proton number were both 1, switching coefficient(α)was 0.558, and the electrochemistry rate constant(Ks)was 0.43207±0.0001 s-1. After mixing the urea into raw milk, the trichloroacetic acid was added to the doped milk, and blended. Clear liquid was obtained by centrifugation that removed the fat and protein. After the clear liquid was tested, it can be seen that, when the concentration of urea mixture was 0.3~2.5 mol/L, urea's concentration had a linear relationship with the peak current value(I_pc=7.7847+3.3098C/(mol/L), r=0.9945). This method's detectability to urea was 0.171 mol/L. Compared with other methods, the pretreatment of this method was simple;the measurement speed was fast;the cost was low and it can be better applied to the industrial line.