Sodium is one of the most common inorganic cations in food. It is mostly added as sodium chloride. Common methods of direct testing include atomic absorption spectroscopy or inductively coupled plasma spectroscopy – techniques requiring expensive instrumentation, costly ultrapure reagents and laborious sample preparation. A straightforward, less expensive and fully automated alternative method is thermometric titration. A detailed description of the method can be downloaded from www.metrohm.com

Thermometric titration uses the rate of change in temperature of the titration solution to detect the endpoint. The sodium determination relies on the exothermic precipitation of elpasolite (NaK2AlF6). The titrant is a standard aluminium solution that contains an excess of potassium ions. The required excess of fluoride ions is provided by ammonium bifluoride, which also serves to buffer the solution to an ideal pH 3.

The method is robust, can be fully automated and copes with challenging food matrices such as ketchup, instant soups, gravies and salty snacks. The titration is performed directly on a suspension of the food sample and is complete in under two minutes.

For further information please visit www.metrohm.com