The measurement of the pH (the power of hydrogen) of a substance tells how acidic or basic a substance is. The pH has a vital role over the control of the course of biochemical and chemical reactions, which is why it is widely used in various laboratories and manufacturing industries.
A pH meter is a very sensitive device and must be handled with great care to ensure that you get accurate results. What follows are eight tips to improve the reliability of your pH measurements.
1. Follow the Manufacturer’s Storage Instructions
Follow the manufacturer’s recommended storage conditions religiously and keep your sensor submerged in 4.0M KCl or pH 4.0 standard buffer when it is sitting idle. Insert the electrolyte filled cap over the sensor bulb if you are looking to keep it in storage for a long time. Never store your bulbs while they are submerged in water as this can lead to changes in electrolyte concentration within the sensor either by leaching to outside water or by transfer of water from outside.
2. Conduct Lab Calibration Services daily
It is mandatory to calibrate the pH meter prior to each use. Rinse out the electrode with purified water prior to submerging it in any solution. Make sure that you don’t wipe the bulb after rinsing it out as this disturbs the glass membrane. It is better to soak the water droplets with a tissue paper.
A single point instrument calibration can be carried out but a three-point calibration covering standard pH buffers at 4.0, 7.0 and 9.0 is advised to cover the entire pH generally faced.
3. Make Sure the Sensor Is Always Hydrated
The sensor should never be dry as a dry bulb will not give correct results. Keep the bulb submerged in a beaker filled with 4M KCl in between your readings. Cover the sensor bulb with a rubber cap filled with 4M KCl if you are planning on storing it for a long time.
4. Maintain the Level of Electrolyte within the Junction Cell
with care to ensure accurate results.
Make sure to inspect the level of electrolyte within the electrode on a regular basis to ensure that the reference wire remains submerged. A dried-out junction will lead to an increased amount of errors along with solid soil deposition at the junction. Make sure that the level is below the filling hole while filling up it up.
5. Prepare the New Electrode
The latest electrodes are generally shipped with rubber caps fastened to the sensor bulbs or tips to maintain the moisture content of the sensor with 4M KCl solution. Make sure that you remove the end cap and rinse out the sensor with de-ionized water.
Make sure to soak the sensor in 4M KCl for roughly half an hour and rinse with distilled or de-ionized water.
Bear in mind that the conditioning of the sensor in water is not ideally recommended as it can damage the glass membrane of the sensor.
6. Remove the Electrolyte Fill Cap Prior to Using
Removing or loosening the cap allows an adequate amount of air to enter and improve the stability of the readings.
7. Make Sure that the Probe is Clean
Always keep your pH probe clean. Dirty probes can lead to erratic results or drifts. Soak the electrode in a cleaning solution which is available commercially for roughly 15 to 20 minutes. Rinse in the water and carefully soak any of the sticking droplets with tissue paper. Do not rub as it can damage the glass. A dirty probe can contaminate the buffer or solution in which it has been submerged.
8. Maintain a Constant Temperature During Observations
All pH measurements depend solely on the weather. Make sure that the temperature does not fluctuate during observations.
The above eight tips are simple to follow and will help you in getting accurate and reliable information every time you take measurements with your pH meter.
About the author
Edward Simpson works for RS Calibration Services and has a knack for finding faults in machines and does not rest until they are rectified to perfection. He lives in Pleasanton, CA and loves to write about how machines work and about the importance of proper care and calibration of equipment. When he's not working or writing, he loves to run to stay fit.