ISE Sensor Calcium Ion Water Hardness Electrode CS6518A Calcium Ion Electrode

Short Description:

The Hardness (Calcium Ion) Selective Electrode is a vital analytical sensor designed for the direct and rapid measurement of calcium ion (Ca²⁺) activity in aqueous solutions. While often termed a "hardness" electrode, it specifically quantifies free calcium ions, which are the primary contributor to water hardness. It is extensively used in environmental monitoring, industrial water treatment (e.g., boiler and cooling systems), beverage production, and aquaculture, where precise calcium control is crucial for process efficiency, equipment scaling prevention, and biological health.
The sensor typically employs a liquid or polymer membrane containing a selective ionophore, such as ETH 1001 or other proprietary compounds, which preferentially complexes with calcium ions. This interaction creates a potential difference across the membrane relative to an internal reference electrode. The measured voltage follows the Nernst equation, providing a logarithmic response to calcium ion activity within a wide concentration range (typically from 10⁻⁵ to 1 M). Modern versions are robust, often featuring solid-state designs suitable for both laboratory analysis and continuous online process monitoring.
A key advantage of this electrode is its ability to deliver real-time measurements without time-consuming wet chemistry, such as complexometric titrations. However, careful calibration and sample conditioning are essential. The ionic strength and pH of samples must often be adjusted using a special ionic strength adjuster/buffer to stabilize pH and mask interfering ions like magnesium (Mg²⁺), which can affect the reading in some designs. When properly maintained and calibrated, the calcium ion-selective electrode offers a reliable, efficient, and cost-effective method for dedicated hardness control and calcium analysis across numerous applications.