At the heart of the potentiometric pH measuring system is the combination pH electrode. A combination pH electrode includes both the indicating sensor made of pH sensitive glass and the reference cell used to generate a stable mV potential. Each have their own design elements that make them ideal for a specific application.
The indicating pH electrode can be made from a variety of different glass types. Glass that is suitable for low temperatures (LT), high temperatures (HT), general purpose (GP) and hydrofluoric acid resistance (HF) are the four types of glass that we use in making a pH electrode. The glass is hand blown into conic, flat tip, bullet and spherical shapes. Each shape has its’ own benefit to an application.
A critical part of the pH measuring system is the reference half cell. In order to provide a steady reference potential the type of junction material is an important decision when building a probe for specific applications. Ceramic junctions are easily fused with glass and are commonly used. For low conductivity samples a probe can have multiple ceramic junctions for a higher flow rate. For food applications in which there is a high solids content a viscolene hard gel is the interface between the sample and the reference cell. This type of junction is referred to as open junction and is resistant to clogging. Other junctions include a removable sleeve design to disassemble and clean, ground glass with a movable sleeve for cleaning, and junctions made from cloth or PTFE materials.
The overall body shape of a pH electrode can be in a variety of shapes, sizes and materials. There are probes with a very small in diameter that can measure as little as 100 μL and very long to be used in an Erlenmeyer flask. The body can be made of glass, PEI or titanium. Each having their own benefit based on its’ intended use.
- BNC – Universal common connector
- Quick Connect DIN
- Digital – 3.5mm
- Digital with matching pin – 3.5mm