This article helps to explain the properties of various pH electrodes that are available, so that you can select the features that will suit your application.
1. Glass or Plastic Body?
Glass body better for corrosive materials or solvents. Withstands temperature above 100°C, more accurate and is easier to clean, but breaks more easily. Blue / amber glass withstands temperature up to 110°C, high sodium or high pH samples.
Plastic is ideal for field use and more rugged applications. Should not be used for high temperature or inorganics.
2. Single or Double Junction?
Economical single junction electrodes are suitable for general-purpose applications.
Double junction are longer lasting, as the electrode is more protected from the solution / contaminant. It is ideal for food, wine, wastewater, biological samples, solutions that contain sulfides, heavy metals or Tris. Non-stick coated junctions are suitable for solutions that may clog conventional glass junctions. When in doubt, the double junction is recommended.
3. Refillable or Sealed Design?
The Sealed design has no refill hole, the reference electrolyte is usually a gel. It requires less maintenance, but replacement of the electrode is necessary when it gets contaminated. It has slightly lower accuracy and a shorter life.
The refillable design has a hole for replenishment and can be used many times.
4. General Use or Specialty Use?
Electrodes for general purpose are economical and usually measure 120 mm (length) by 12 mm (diameter). They usually have a 1m cable and a BNC connector.
Effective for specific applications. See the examples below.
- pH Spear / Spear tip are specifically designed for measuring solid and semi-solid samples such as cheese, meat, fruit, bread or other similar samples.
- Open pore electrode for samples high in proteins, creams, fats and cosmetics.
- Sleeve type electrode ensures high electrode flow, so it is ideal for low ionic strength and viscous samples.
- Flat surface tip electrode for flat samples like paper or cloth.
- Micro stem electrode fits into thin stem NMR tubes or small vessels.
- Durable tough bulb electrode that is resistant to breakage
- pH Electrode for high viscosity solutions such as emulsions, suspensions, paints and varnishes where frequent cleaning is necessary.
- pH Electrode for measuring the pH of soil.
- pH and ORP (Oxygen Reduction Potential) Electrodes that also judge how much oxidation or reduction takes place under existing conditions. Useful in the treatments of industrial wastes, study of biological systems, oxidation of cyanide, bleaching of pulp, manufacture of bleach and reduction of chromate wastes.
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