Measuring calcium and chloride in milk

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Calcium is an important mineral and component of a balanced diet. It helps to build and maintain strong bones and teeth, but it is also very important for other physical functions, such as muscle control and blood circulation. Milk and milk products are one of the most common natural source of calcium. Cow’s milk has good bioavailability of calcium and it isabout 30 to 35%. It is estimated that without consuming milk and milk products in the diet, ledd than half of the calcium requirements would be met.
Determination of Calcium in milk sample by titration
The determination of calcium in milk is based on a complexometric titration of calcium with an aqueous solution of the disodium salt of EDTA at high pH value. The method uses a very large molecule called EDTA which forms a complex with calcium ions. EDTA stands for ethylenediaminetetraacetic acid. A blue dye called Patton and Reeder’s indicator (PR) is used as the indicator. This blue dye also forms a complex with the calcium ions changing colour from blue to pink/red in the process, but the dye–metal ion complex is less stable than the EDTA–metal ion complex. As a result, when the calcium ion–PR complex is titrated with EDTA the Ca2+ ions react to form a stronger complex with the EDTA.
For determination of calcium in milk sample by titration you can use


Automatic Potentiometric Titrator
The HI931 Automatic Titrator is the answer to your dedicated titration needs. Fully customizable, the HI931 delivers accurate results and intuitive user experience, all in a compact package. Titrate for a variety of measurements at the push of a button including acids, bases, redox, and selective ions. No additional programming upgrades to purchase. The only things you need to start using the HI931 are a sensor and titrant.
  • Small footprint so you can fully optimize your benchtop.
  • Unmatched 40,000-step dosing pump for small volumes of titrant to help you achieve a very precise endpoint for greater consistency.
  • Flexibility to store up to 100 methods.
Determination of Calcium in milk sample by ISE
Potentiometry is a simple electrochemical technique applied in research laboratories for the determination of free calcium ion activity in milk and dairy products. This analysis is simple to conduct, it has relatively fast response, reasonable selectivity, wide linear dynamic range, simple instrumentation and relatively low cost and continuous monitoring.
This technique is currently adopted in research laboratories to investigate physicochemical, nutritional and technological properties of milk and rennet gels.
Determination of Calcium in milk sample by ISE use HI4004 and HI4104.
The HI4004 is a liquid membrane, half-cell ion selective electrode (ISE) for the determination of calcium (Ca2 ) in solution. The PVC membrane comprised with organic ion exchanger produces a potential change due to the calcium ion exchange between the organic polymer membrane and the sample. The internal sensing elements are housed within a durable epoxy body. The HI4004 is ideal for a variety of applications in the food and beverage industry and water analysis.
  • Liquid membrane sensor
  • Detection from 0.12 to 40,080 mg/L Ca2
  • For use with HI5315 reference half-cell


Calcium Half-Cell Ion
Selective Electrode


Calcium Combination
Ion Selective Electrode


Added sodium chloride in milk is practiced with the aim of increasing the density of milk as well as the ash content in milk which has been adulterated with water. This analysis also allows food labs to quantify the concentration of salt in products such as cheese and other milk products. Mineral composition of milk is also modified during mastitis and this specially concerns concentrations of sodium and chloride ions which are strongly increased.
Determination of chloride in milk sample by titration
Chloride is extracted from samples by mixing in warm water, or directly from ready-to-feed products. After (optional) precipitation of proteins, chloride ions are titrated with standardized AgNO3 solution potentiometrically, using a silver electrode to detect the end point.
Tajana Mokrović, mag.nutr.

ISO 12081:2010(en) Milk — Determination of calcium content
ISO 21422 IDF 242:2018 Milk, milk products, infant formula and adult nutritionals — Determination of chloride — Potentiometric titration method