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Traditional analytical techniques for sodium determination are complex and time consuming. In this study, sodium content in food samples was determined by potentiometric multiple standard addition technique with a sodium ion-selective electrode. The results were compared with results obtained with classical analytical methods for sodium content determination (AAS, IC and ICP-MS). The comparison indicates that sodium content in food samples can be determined directly, quickly and accurately by potentiometric multiple standard addition. This analytical technique represents an alternative to sophisticated analytical techniques for routine analysis and quality control in food production.
Sodium is an essential ingredient in processed foods, but too much can be detrimental to health. Accurate and efficient sodium determination is therefore necessary during food production and quality control processes. It has to be reliable, accurate, precise, straightforward, and fast. Some of the commonly used methods for direct sodium analysis are atomic absorption spectroscopy (AAS), ion chromatography (IC) or inductively coupled plasma mass spectroscopy (ICP-MS). However, not only do these methods involve tedious sample preparation and time-consuming system calibration procedures, they also require significant capital investment and in-depth user knowledge. In contrast, the potentiometric multiple standard addition technique stands out as a simple, fast, reliable and economic method to accurately determine the sodium ion content in food products.
Principle of the Multiple Standard Addition Method
The sodium determination is performed with ion-selective sensors. As the membrane potential cannot be observed directly, the membrane potential of the ion-selective electrode (ISE) half-cell is measured against a reference sensor. First, the electrode potential (Ex) of the sample solution is measured in mV. Then, a small amount of sodium standard solution (∆Vs), of known concentration, is added to the sample solution several times in succession. The addition of the sodium standard increases the sodium concentration (cs) in the sample. The potential (Es) of the sample mixture is measured after every addition. The differences in potential (∆E) resulting from the known volumes (∆Vs) of added standard are used to determine the sample concentration directly with an iterative evaluation algorithm, which is based on the Nernst...