Probes, Spectrometers and Chemical Test Kits
Reduce the cost of pH measuring
We are often confronted with pH meters of many different brands that apparently do not work properly. On most of these occasions all that is required is to clean the probe properly. In many cases once cleaned, the probe and meter functions perfectly.
If this does not work the most common problem is that the probe needs replacement. Another common problem is corrosion on the electrical connectors between the meter and the probe. One of the other most common causes for rapid probe failure is poor probe selection. We can help with free advice in selecting the correct probe.
A pH probe is a small electric cell that generates DC electricity in the milliVolt range (Household power is 220Volt AC, Car Battery 12Volt DC) The Voltage of this cell depends on the pH of the solution it is immersed in. The electrolyte inside the probe cell needs to be in ionic contact with the solution to be measured. This contact occurs via the Junction. In Hanna pH probes there are a variety of junctions. The cheaper probes have cloth junctions, then there are porous ceramic junctions, some probes with single ceramic dots others with up to three ceramic junctions. The most modern junction technology features open junctions and PTFE junctions. pH 7 yields almost no current.
Therefore, if your pH probe reads in the vicinity of 7 and refuses to budge or moves very slowly when transferred to buffer 4 or 10 Calibration fluids, there could be four problems;
- The Electrical connections fail to conduct the generated power to the meter. Clean the connections and check if there is a short circuit. A short will cause a constant reading close to 7.
- The Junction is clogged. Most Commonly because the operator lost the cap, allowed the probe to dry, allowing the electrolyte to cristallise and clog the junction. This normally manifests itself in a slow small stepped change when the probe is exposed to widely differing solutions. Cloth junctions can be re-opened by pulling the tape out about 4mm this places a clean section of tape in the orifice, allowing flow. An old soft Toothbrush, used gently can help to scrub the outside of the junctions. Then cleaning with a suitable Hanna Cleaning Solution normally does the job. Resulting in a probe that positively Gallops to the next reading when exposed to a widely different pH solution.
- The pH Sensitive glass of the probe is covered with Fat, Oil or Protein. This will depend on the fluids you measure Eg. Milk contains both Fats and Proteins etc. Again exposure to a suitable Hanna cleaning Solution with gently soft Toothbrush scrubbing can do the job.
- The electrolyte inside the probe has been contaminated, leached or diluted. Do not store the probe in Distilled Water for any duration, USE Hanna Storge Solution
All pH probes use the same or very similar chemistry so, Hanna Solutions can be used regardless of the brand of Meter or Probe you use.
Hanna Replacement probes can be used with most brands of pH meters, (Talk to us) Hanna is one of the largest manufacturers of pH probes in the world, so you can get the price benefit of their large production volumes.
- If you have any question related to any of the articals presented here, then please don't hesitate to contact us.