pH value measurements are widely applied across a wide scope of fields, including environmental monitoring, agriculture, food and beverages, chemical engineering, pharmaceuticals, sewerage and tap water, as well as quality inspections and scientific research. A knock-on effect of it being a useful metric for several areas is that the equipment needs to test various types of samples and in very different test environments. Users can experience difficulties when taking pH measurements, not only consuming time but also providing incorrect test results. It can be difficult to get to the root of the cause quickly in these cases.

Here are some tips from OHAUS to make pH measurements easier for you.
 
1. I’ve just changed the electrode, so why is the display indicating that it is in a poor condition (slope is wrong)?

Quick Tips:
Possibility 1: Did you calibrate your new electrode after you changed it?
 
Solution: When you change an electrode, you must also calibrate it. Only once this has been done, can the instrument display the new electrode’s state.
 
Possibility 2: Temperature change may also influence the electrode state.

Solution: The OHAUS pH meter can automatically make corrections for the influence of temperature on the buffer solution to ensure accurate measurements.
 
2. How do I store the pH electrode to keep it in good condition?

Quick Tip:
Most electrodes are made of glass and are fragile - requiring correct maintenance and storage for a long service life, and to deliver precise and reliable measurement results.

Different storage and protection methods are necessary depending on how frequently you use the electrode.

We can categorize use-frequency into three types.

Type 1: Between Measurements (use within one hour)
Storage: Please leave the electrode in air rather than in distilled water.

Type 2: Short-term Storage (use within one week)
Storage: Place the electrode in the electrode storage solution specified in the handbook. If you do not have a ready-made solution, a temporary one can be prepared by adding 1g KCl into 200mL pH7 buffer solution.

Please do not put the electrode into a distilled water or deionized water. Otherwise, it may suffer the leakage of ions out of the glass microsphere or reference solution, which will result in slowed electrode response and shorten the service life of the electrode.

Type 3: Used very infrequently and the electrode needs to be stored for longer than one week.
Storage: The electrode storage solution is preferably 3mol/L KCl solution. For electrodes that can be placed in liquid, you need to use the reference liquid which is a 4M KCl solution containing AgCl.
 
3. How long is the service life of the electrode?
 
Quick Tip:
A good performance and long service life relies on the user using, storing and maintaining the electrode according to the recommended procedure. It will also be affected by the physical and chemical properties of the sample to be tested as well as the temperature.

If maintained well, a pH electrode can normally have a service life of about 6 to 12 months.

Please make sure you choose an appropriate electrode to match the sample. If the electrode is used to measure strong acid, alkali/corrosive samples/high-temperature samples, etc. or is maintained improperly, its service life may be only a few weeks to a few months.
 
4. Why can’t a new electrode be calibrated or the numerical value is unstable?
 
Quick Tip:
This abnormality is normally caused by a bubble in the sensitive membrane or gel of the electrode..
 
1) You need to remove the bubble. The electrode you can use force to move the bubble down (like with thermometer) and expel the bubble. If not in regular use, the electrode should be placed in a vertical position.
 
2）The sensitive membrane of the electrode may have gotten dry over time. Thus, it needs to be activated by putting it into a solution of 3mol/L KCl.
 
 
5. Why is the pH value measured by the electrode unstable?
 
Quick Tip:
Does the following apply to your electrode?
 
If your electrode has a very short response time when used to measure the buffer solution but when used to measure the sample it takes a long time and is not easy to get a stable reading. This indicates that the electrode is unsuitable to measure the sample. For example, a conventional electrode is used to measure the sample such as tap water, rain water, purified water or distilled water. If so, you need to buy or change a suitable electrode to carry out your measurement.