Food scientists, agronomists, and chemists frequently need to know the amount of calcium present in a variety of solutions. Different solutions, however, may require different electrodes.

A new Calcium Ion-Selective Electrode (ISE) from Hach Co. can measure calcium in almost all aqueous sample types, including colored and turbid samples, according to the manufacturer. Applications include measurement of calcium in milk, wine, boiler feed-waters, feeds, plant tissues, and beer. The Hach Calcium ISE uses a solvent-polymer membrane containing an organophosphorous ester as a calcium ion carrier, in an inert polyvinyl chloride plastic matrix. Its extremely low solubility calcium electrode is said to result in improved electrode life and performance, and the, replaceable membrane modules and refillable internal filling solution provide convenient, economical operation. An internal silver-silver chloride element, in contact with the internal filling solution, establishes a fixed potential. The ion-selective membrane undergoes ion exchange with calcium in the sample, creating...

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