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 ν^1/2(I_pc=5.7410ν^1/2-0.07706, r=0.99784;I_pc=18.9488ν^1/2-1.1299, 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.