Chloride in Mayonnaise
The chloride is extracted from the sample by dissolving in 1 Molar nitric acid which also acts as an ionic strength adjustment buffer.
Equipment Required
2. 3261 Chloride Combination ISE
3. 21301 Chloride 1000ppm Standard Solution
4. Nitric Acid Solution (1 Molar)
5. Glassware. Beakers 250ml, Volumetric Flask 100ml. 10ml Graduated pipette
6. Deionised water.
Preparation of 1.0 Molar HNO3
Take appropriate care with Conc Acids. Wear eye protection and gloves.
To 900ml of deionized water add 62.5ml Conc.HNO3. Dilute to1000ml. This is 1M HNO3.
Prepare 0.5Molar HNO3 by diluting 50:50 with deionized water.
Standard Preparation
Prepare standards of 100, 10ppm by serial dilution of the 21301 1000 ppm Standard solution. This is best achieved by pipetting 10ml of the standard into a 100ml volumetric flask and diluting to the mark with the previously prepared 0.5 Molar HNO3. This is now a 100ppm Standard.
Sample Preparation
Weigh accurately Ig of sample and disperse in 500 ml of ISAB in a volumetric flask. Mix the solution vigorously to ensure complete mixing. Dilute to 1 litre with deionised water. Filter the sample solution (a Whatman No. 541 filter is suitable) into a clean stoppered flask.
Method
Pour 100ml of each of the standards and samples into clean beakers. Be sure the beakers are clean and make sure not to touch the inside of the beakers with bare hands as Chloride contamination from sweat etc. is common. Beakers that have been washed with softened water or tap water will be contaminated. In these cases rinse the beakers with deionised water.
Immerse the electrode in each of the standards in increasing concentration steps following the calibration routine on the Ion Meter, rinsing the electrodes with distilled water and dabbing off the excess water between standards. Measure the sample.
Using the DR359TX Ion meter will allow the result to be read directly on the display. It also allows for up to a 5 point calibration if required.
If you do not have an ION meter you can read the mV values using a pH/mV meter such as an EDT model FE257. Record the mV response and plot a graph of mV vs. log of Concentration.
Calculation.
The result on the display will correspond to mg Cl in 1g of sample. To Get % Chloride in Mayonnaise divide the result by 10.
Interferences
There are no interference from up to 500 ppm S=, 1000 ppm