pH measurement has become a critical control parameter in research, product development, manufacturing operations and clinical diagnosis. This means that the measurement requires special considerations depending on the nature of sample, available quantity and volume. Apart from laboratory measurements pH plays a crucial role in online measurements, soils, fruits and vegetables, meat products, processed foods, swimming pools and spas, etc.
The present article covers the range of pH electrodes available for different laboratory and field applications
Gel Filled Electrodes
The glass electrode is most common in laboratory applications. It is the ideal choice for solutions containing buffers, proteins, corrosive solutions or organic solvents. Polymer sleeve body electrodes are more durable than glass and are more suited for field applications.
Generally electrodes are either refillable or gel filled. Gel filled electrodes exhibit ruggedness for a number of applications. The gel needs to be replaced after six months to one year.
Spear Tipped Electrodes
Spear tipped electrodes are ideal for semi-solid samples such as gels, plants, fruits, meat, cheese, etc. The electrode features a durable measuring glass spear shaped tip for piercing the sample. It is easy to clean and such electrodes are designed especially for food applications.
Submersible pH Electrodes
Submersible electrodes are made of inert material for use in drums, tanks, streams, etc. The flat sensing end is surrounded by a porous polythene reference junction which minimizes fouling
Micro and Semi-Micro Electrodes
Micro-and semi-micro electrodes are designed to measure pH of small micro volume samples. Such electrodes directly fit into well plates, NMR tubes, micro-centrifuge tubes and serum cups. Measurements can be made down to 10 µL volumes. Solid-state body makes such electrodes unbreakable.
Flat Surface Electrodes
Flat surface electrodes are made of epoxy body with a flat sensor glass bulb that permits measurement of pH of moist flat solid surfaces such as skin. The sample must be moist enough for the pH sensing bulb and reference junction to make contact with the sample. If required, add a drop of distilled water or KCl solution to wet the surface before placing the electrode on the sample. Highly reproducible results would require same amount of liquid addition before taking the measurement.
pH electrodes have many manufacturers due to growing demand of industry ,research bodies, hospitals and college/ school laboratories. Some of the reputed manufacturers supplying various electrode versions are:
- Cole Palmer
- Thermo Scientific Orion
- Nengshi Analytical Sensor Co Ltd
Your comments and suggestions are always welcome.