The concentration of calcium is determined directly by using the technique of standard addition.
- Ion analyzer (recommended) or pH meter with millivolt scale.
- detectION 3041 calcium ion selective electrode
- Calcium standard solution O.1m CaCl2: Dissolve 11.1g of Calcium Chloride into distilled water in a volumetric flask and dilute to 1000 ml.
- Sodium hydroxide solution 1.0m NaOH: Dissolve 40g of NaOH into distilled water in a volumetric flask and dilute to 1000 ml.
Take 150 ml of beer sample and pass through filter paper to equilibrate CO2 content with air. Adjust the pH of the sample to 5.5 - 6.0 pH with 1.0m NaOH if necessary.
Place electrode into 100 ml of prepared sample, stirring thoroughly. Record the electrode potential mV1. Add 1.0 ml of O.1m CaCI2 standard to the sample solution, stirring thoroughly and allow the reading to stabilize. Record the new electrode potential, mV2.
Use the equation for standard addition. Appendix 1 Section 5. The E value will be given by mV2 – mV1. The slope of the electrode should be +29mV. This can be checked by running a calibration curve of 3 known CaCl2 solution concentration.