Collaborative study of a potentiometric titration method for determining sodium chloride in foods
Brammell, W.S.
Journal - Association of Official Analytical Chemists 57(5): 1209-1216
1974
ISSN/ISBN: 0004-5756 PMID: 4412504 Document Number: 78430
The official final action potentiometric titration method for NaCl 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 AgNO3. The method is applicable to levels of more than or equal to 0.03% NaCl. As in all methods involving precipitation of chlorides with AgNO3, bromide and iodide interfere but not significantly at the levels found in most foods. Interference by protein, amino acids, and phosphate, hydroxyl, carbonate, sulphate, and fluoride ions is prevented by acidifying the sample. In the collaborative study, 10 collaborators successfully analysed 12 different foods, obtaining a coeff. of variation of 1.0% for Parmesan cheese, an indication of the precision of the method. Potentiometric titration of chloride in ashed and non-ashed samples gave close agreement for NaCl 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 NaCl 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.