Because direct measurement methods have been cost and time-prohibitive for testing labs – many food companies have indirectly analyzed sodium through the analysis of chloride – but this can yield highly inaccurate results. Here’s a fast and economical direct-testing method to accurately measure sodium content.
Sodium in dairy products
Conventional, indirect approach: precipitation reaction with silver nitrate
The sodium content of beverages is usually determined indirectly through a precipitation reaction with silver nitrate.This approach assumes that the chloride ions are present in a molar ratio of 1:1 with the sodium ions, which is not always the case. On the other hand, established methods for the direct determination of sodium such as AAS or ICP/MS are very expensive.
Better alternative from Metrohm:
Thermometric titration is a cost-effective and straightforward alternative.
Thermometric titration is a cost-effective and straightforward alternative. First, proteins in the milk sample are precipitated with trichloroacetic acid and then separated through filtration or centrifugation. An aliquot is titrated in the presence of NH4F at a pH value of 3 with an aluminum nitrate solution with an excess of potassium ions. The exothermic reaction produces insoluble NaK2AlF6.
For applications and more know-how check out our page on Milk and Dairy analysis.