Hanna HI 1131B Laboratory pH Electrode

The HI1131B is a glass body, refillable, double junction pH electrode with a BNC connector. This electrode has a single ceramic junction in the outer reference cell and the spherical pH sensing portion is made with high temperature glass.

This design consideration is ideal for laboratory samples, beer and other liquid samples, as well as general purpose use.

The measurement of pH at very high temperatures is detrimental to the sensitive glass bulb and will shorten the life of it. A pH electrode with general purpose (GP) glass will have a resistance of 100 megaohms at 25oC while the resistance of HT glass is around 400 megaohms at 25oC. As the HI1131B is used at elevated temperatures the resistance decreases to approach the that of GP glass. The HI1131B is suitable to use with samples that measure from 0 to 100oC.

The spherical bulb is for general purpose use. Other tip shapes include conic for penetration and flat tip for surface measurements.

The glass body is ideal for laboratory use. The glass is resistant to many harsh chemicals and is easily cleaned. The glass body also allows for a fast transfer of heat to the internal reference electrolyte. The mV generated by the reference cell is temperature dependent. The faster the electrode reaches equilibrium, the steadier the reference potential.

The HI1131B is a double junction design. pH electrodes are available as single junction or double junction. See below for a complete description of the differences. The junction also known as a salt bridge is necessary component of the electrical circuit. The movement of ions must flow through the junction for a steady reading. The outer reference has a single ceramic frit. The ceramic is a porous material that is easily fused with the glass body and has a similar expansion coefficient. A single ceramic junction has a flow rate of 15-20 μL/hour. Other junction types are available with higher flow rates and made with different materials.

The HI1131B is a refillable probe. Since it is a double junction pH electrode the fill solution is the HI7082 3.5M KCl. This solution does not contain any silver as with single junction electrode. The absence of silver will prevent any silver precipitate from forming at the junction surface and clogging it. Clogging of the junction will result in drifty and erratic readings.  

The HI1131B uses a BNC connector. This type of connector is universal in that it can be used on any pH meter that has the female BNC probe input. Other type of connectors include DIN, screw type, T-type, and 3.5mm to name a few. These types of connectors tend to be proprietary for a particular type of meter and are not interchangeable.