07/02/2015

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Determine sodium titrimetrically

Metrohm International



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In the presence of an excess of potassium and fluoride ions, sodium reacts exothermically with aluminum to produce NaK2AlF6 (elpasolite). This reaction is the cornerstone of a new method for determining sodium in foodstuffs using thermometric titration. Not only is it rapid, straightforward, and reliable, but the method can also be automated which makes it ideal for routine checks - even within the process itself.

Absorbing large quantities of sodium in the diet - through table salt, for example - can have a negative impact on health. Numerous jurisdictions have responded to this issue by ruling that food packaging must specify sodium content.

That was then: The trials and tribulations of titration

To date, titrimetric sodium has commonly been determined using an indirect method that determines not the sodium, but in fact the counterion chloride using argentometric titration. In the end, it is the stoichiometry of sodium chloride that is used to deduce the sodium content. There is one flaw in this method, however, which is that not all sodium in food occurs with chloride as a counterion; as a result, it tends to underestimate the actual sodium concentration.

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