Chloride ion concentration in milk was determined by pulsed amperometric detection in a flow injection system. Results showed that the Au electrode lost 3 electrons at 1.10 V and formed chloroaurate ions (AuCl) by combining with chloride ions, after which AuCl was partly reduced to Au at 0.6 V. Based on the electrochemical process, a triple waveform with detection potential of 1.15 V, detection time of 150 ms, oxidation potential of 1.4 V, oxidation time of 550 ms, reduction potential of 0 V, and reduction time of 400 ms was applied to the Au electrode for detecting chloride ion concentration in milk. The approach is rapid and automatic and features a detection limit of 0.005 g/L. The relative standard deviation obtained by 60 repetitive injections reached 1.48% at 2 g/L of NaCl. The method developed using the Au electrode without modification was used to analyze the chloride ion concentration in raw milk without preprocessing. The method showed good agreement with potentiometric titration.

The relationship model of chloride ion content and oxidation peak current was established by the study of curve obtained by using gold electrodes to test cyclic voltammetry in raw milk containing different chloride ion concentrations. The study found that with the increased of chlorine ion content, the potential of the oxidation peak was in positive correlation and the current of the peak increased dramatically. The golden matter appeared in sample liquid. In addition, we observed that corrosion in gold electrode, and the characteristic peak of Au-Cl -1 appeared at 269cm -1 by using SEM and SERS to detect the reaction electrode. The results showed that the gold electrode had the anodized dissolution because of the presence of chloride ion. The prediction model of chloride ion content with a detection limit of 0.05g/L was established by the least square method. The recovery rate and relative standard deviation of the method were respectively from 91.0% to 106.0% and from 3.4% to 4.2%. The method is suitable for rapid detection of milk mixed with salt. 1 Huang Gan-hui, born in 1967, is a professor in Nanchang University, who acquired his doctorate degree from the same university specializing in food engineering.Chen Xing-guang, born in 1993, is now studying food engineering in Nanchang University. He focuses his research on food safety and electrochemistry.Chu Bei-bei is now Studying food engineering in Nanchang University. She focuses her research on food safety and electrochemistry.Lai Li-zhi, born in 1991, is now studying food engineering in Nanchang University. She focuses her research on food safety and electrochemistry.Peng Hui-feng, born in 1994, is now studying food engineering in Nanchang University. He focuses his research on food safety and electrochemistry.Deng Dan-wen is a Professor in Nanchang University specializing in food engineering. She focuses her research on food safety and electrochemistry.