In the presence of an excess of potassium and fluoride ions, sodium reacts exothermically with aluminum to produce NaK2AlF6 (elpasolite). This reaction is used for the thermometric titration of sodium in foodstuffs. As the reaction is exothermic, the temperature rises, and the point at which the temperature curve bends marks the endpoint. This makes it more reliable compared to the classical argentometric titration with chloride.
Several foods were analyzed, namely bouillon, gravy, tomato ketchup, corn chips, pretzel sticks, as well as crackers. The samples were simply crushed and homogenized before titration. The reproducibility of the results was good with relative standard deviations between 0.08% and 3.75%.
In addition to this Application Bulletin, you can find more information on thermometric sodium determination in foods in our application video: