Abstract
The official final action potentiometric titration method for sodium chloride in canned vegetable products was modified to provide a general quantitative method for foods. The product is dispersed with water and acidified, and soluble chlorides are titrated potentiometrically with silver nitrate. The method is applicable to levels of ≥0.03% sodium chloride. As in all methods involving precipitation of chlorides with silver nitrate, bromide and iodide interfere but not significantly at the levels found in most foods. Interference by protein, amino acids, and phosphate, hydroxyl, carbonate, sulfate, and fluoride ions is prevented by acidifying the sample. In the collaborative study, 10 collaborators successfully analyzed 12 different foods (beef broth, soy sauce, salted whole eggs, margarine, prepared mustard, baby food (carrots), bread, TV dinner, parmesan cheese, canned salmon, ham, and peanut butter), obtaining coefficients of variation ranging from 0.49 to 5.99%, an indication of the precision of the method. Potentiometric titration of chloride in ashed and nonashed samples gave close agreement for sodium chloride content, showing that protein and other organic matter present do not interfere, that ashing is not necessary, and that dispersion or blending with water is adequate for sample preparation. With the proposed method, the sodium chloride content of a food sample can be determined with precision and accuracy in 2—6 min. The method has been adopted as interim official first action.
