The HI4112 lead/sulfate 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 nitrate electrolyte. The internal elements are isolated from the sample by a compressed lead sulfide sensing membrane.

Hanna’s solid state 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 HI4112 to measure lead accurately, it is important that the ionic strength of the standards and sample be adjusted to a high and constant value with the lead ionic strength adjuster (ISA) solution. The ISA ensures that the activity coefficient is constant so the concentration of free lead ions can be measured. Measuring all solutions with a constant ionic strength reduces the margin of error between measurements. The HI4112 lead/sulfate solid state ISE can measure from 1µM (0.21 mg/L) to 0.1M (20,700 mg/L).

The HI4112 can also be used as an indicator to follow the progress and detect the endpoint of a precipitation titration of sulfate. During the titration, the lead/sulfate ISE follows the lead concentration while a lead perchlorate solution is used to titrate the sample. The lead in the titrant solution reacts with the sulfate ions present in the sample to form a precipitate. Once all of the lead and sulfate ions have reacted, a change in mV occurs to signal the endpoint, and ultimately the sulfate concentration.

Conversion Table for Pb2+