Detection of Chloride Ion in Raw Milk by Electrochemical Method

Electrochemical reaction mechanism of silver electrode in chlorine ion test solution was discussed by cyclic voltammetry, and based on this, an electrochemical method for rapidly detecting chloride ions in raw milk was established. The results showed that when the silver electrode in the chloride ion test solution was positively scanned, silver oxidized to silver ions due to lose an electron, then combined with chloride ions in solution to form silver chloride precipitate. When the silver electrode was negatively scanned, silver chloride was reduced to silver. After the salt was mixed in the raw milk, the raw milk sample was dissolved with 10% trichloroacetic acid, and the protein and fat in sample were removed by centrifugation, then 1 mol/L Na₂SO₄ was added to the centrifugal liquid to obtain an extract solution. After detecting the extract, it could be seen that the silver electrode produced a pair of redox peaks, and the peak current was linear with the concentration of chloride ions in the raw milk in the range of 0.03~0.21 mol/L. The detection limit of this method was 0.001 mol/L, and the recovery and relative standard deviation were 93.3%~113.7% and 2.33%~4.89%, respectively. There was no significant difference compared with GB5009.44-2016.The method had simple pretreatment, fast measurement and low cost, and could be applied to the actual production line.