Measurement of Cl- Concentration in Milk

The high casein content of milk can be adsorbed on the electrode and on the current bridge. This adsorbed protein layer can break down the potentiometric signal. Therefore, the dilution of the sample as well as the standards is necessary. For the milk samples, the addition of the ISAB solution, in this case, 2 volume of the diluted aqueous HNO3 solution to 1 volume of milk or standard is recommended, that is, the 2 1 ratio is recommended. The ISAB is prepared by diluting 60 cm concentrated HNO3 to 11 with de-ionized water. 

One gram of a meat sample is sonicated in 100 cm water. The obtained dispersion is filtered. Twenty-five cubic centimeters of the filtrate is mixed in the 1 1 volume ratio with 0.5 M nitric acid used as an ISAB solution. The same ratio of the ISAB is added to the calibrating standards. The usual direct potentiometric method gives the chloride ion concentration of the extracting solution. The sample concentration is given as micrograms per gram of meat. 

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