Comparison of different methods for determination of sodium chloride in cheese

Abstract

The content of NaCl (weight fraction of Cl-ions, in %) was analysed in different cheeses, which were bought in supermarkets, and made by domestic manufacturers. Sodium chloride in cheese samples was analysed after the extraction of chloride by nitric acid solution. Concentration of chloride ions was potentiometricly determined, with the chloride selective electrode and titrimetricly by Volhard method. According to the results in the analysis of the content of NaCl in %, by different methods it was determined that the share of NaCl in % ranged from 0.66 to 4.43% (determined by potentiometric route) that is from 0.97 to 4.72% (determined by titrimetric route by Volhard method). The difference in received results in different methods is less if the share of NaCl, in % is higher than 3%. If the share is less than 3%, the difference in results rapidly increases, and the biggest difference is when the share is less than 1%. This analysis was done according to the results received by Volhard method, which is accepted as a standard method. As Volhard method is in connection with cheese resolving by intense oxidation means, azotic acid and potassium permanganate, obligatory in fume board (hood), it is not a practical method. On the other hand, the potentiometric method with usage of the chloride-selective electrode is very simple and gives reliable and reproductive results. In case of a small content of NaCl, in %, higher precision and accuracy of determination by chloride-selective electrode can be obtained by indirect measurement of chloride-ions (by standard addition method).