Determining Salt in Food

Refractometers can be the easiest to use with low equipment cost and no chemicals required, but are not selective to sodium chloride and therefore, can only be used for quantitative measurements in binary solutions.

The sodium ISE is can be beneficial to a QC protocol due to its high accuracy and direct determination of sodium. Several other methods, including titration and refractometry, infer sodium from another measurement. The sodium ISE is the only method truly specific for sodium, making it ideal for foodstuffs with complex matrices. However, the required daily prep time for calibration and electrode care is high, and requires excellent laboratory technique in order to obtain accurate measurements.

In both manual and potentiometric titrations, sodium content is inferred from chloride concentration. This can be problematic for complex samples that contain other chloride salts or other sources of chloride that are not sodium chloride. For example, magnesium chloride and calcium chloride are commonly added to tofu as coagulants, therefore rendering a chloride titration infeasible at determining sodium content.

Manual titrations may be insufficient in accuracy and repeatability due to the subjectivity of determining the titration endpoint from a color change, and the coarse dosing resolution of manual burettes. Automatic titrators can be the easiest to use with the potential for the most accurate methods, with typical %RSD of <1% to 2%. Potentiometric titration is also recommended for many of the titrimetric methods contained within the AOAC standard methods of analysis. However, the capital investment can be the highest among the other mentioned methods.

The ideal method can change depending on the specific product, but in all cases, all available methods should be reviewed for their ease of use, accuracy, and costs.

Masulli is application engineer at HANNA instruments. Reach him at [email protected].