1.Why pH value is different in one sample if measured two times ?

pH value will be changed if there is temperature change or chemical reaction in water sample,so user should keep temperature constant and avoid chemical reactions.

2.Why the pH value is different by two pH meters to measure same water sample and at the same time?

the measured pH values are different ,because the calibration conditions of the two pH meters are different (such as temperature,buffer etc).Therefore, the pH meter should be calibrated at the same time in the same buffer and then measured in water sample simultaneously.

3.How often does the pH electrode need to be calibrated?

The calibration period of pH electrode depends on the specific conditions of the pH electrode's use, maintenance, sample properties, and measurement accuracy. Usually 3~6month for online pH electrode. Every day calibration for laboratory pH electrode, however users must calibrate pH electrode when not use in long time or replace new pH electrode.

4.How to store the pH electrode ?

pH electrode should be stayed in 3mol / L potassium chloride solution (3M KCl) if not use.It also can be stored in pH 7.00 buffer for a short time.the working life of pH electrode will be shortened if immersed in distilled water or in dry state.

5. How to maintain the PH electrode?

If slope of pH electrode become low,response is slow after use a period time,then users can try below methods to maintain pH electrode

1) If the water sample contains protein, the pH electrode can be washed with a pepsin/hydrochloric acid.

2) If the water sample is with oily/organic liquid, it can be washed with acetone or ethanol.

3) If the electrode junction is found to be dirty or black, user can use mercaptan liquid to clean the junction.

Activate the pH electrode : put pH electrode in regeneration solution 30 seconds, and then immersed in a 3 mol/L KCl solution for 5 hours.