The HI4104 calcium ion selective electrode is a complete potentiometric cell that contains a silver/silver chloride (Ag/AgCl) reference housed within a PEI plastic body with a potassium chloride electrolyte. The internal elements are isolated from the sample by an organic polymer sensing membrane.

Hanna’s liquid membrane combination ISEs are designed with a cone style junction. The skirted cone geometry of the sensor forms the liquid junction with the test solution at the tip of the junction cone, producing a highly stable reference potential and consistent flow rates of electrolyte into the solution. A simple press of the top portion of the ISE makes it easy to empty the electrolyte fill solution and replace when necessary.

For the HI4104 to measure calcium accurately, it is important that the ionic strength of the standards and sample be adjusted to a high and constant value with the calcium ionic strength adjuster (ISA) solution. The ISA ensures that the activity coefficient is constant so the concentration of free calcium ions can be measured. Measuring all solutions with a constant ionic strength reduces the margin of error between measurements. The HI4104 calcium liquid membrane ISE can measure from 3µM (0.12 mg/L) to 1M (40,080 mg/L).

Conversion Table for Ca2+