How to detect the quality of the pH meter electrode?
Users can check the quality of the pH electrode by themselves according to the data in the table below, the steps are as follows (adjust the pH meter to the mV range)
⑴ Test the zero potential pH value, zero point pH value: 7±0.5pH pH electrode inserted into the pH4.00 buffer solution, read after stabilization (pre-test the temperature of the solution). For example, at 25°C, the reading value E1'=186mV (value), and the accurate value is 178mV (see table), then the error value=186-178mV, converted into pH value: 8/59.16=0.14pH (59.16mV/pH is K value at 25°C, see table). Therefore the zero pH value is acceptable. Generally, the zero potential error of a new electrode is ≤±0.3pH, if the zero potential error is >±0.5pH, the test error of the electrode will be relatively large, especially when the temperature of the test solution changes greatly. If the test accuracy is not high, the zero potential error value can be larger, but the maximum can not exceed 1pH.
⑵ test electrode percent theoretical surplus rate (PTS)
Record the test data in step (1) of 186mV, clean the electrode and insert it into the pH9.18 buffer solution, and read after stabilization, E2'=111mV (value), ΔE'=E1'+E2'=186+111= 297mV, compared with the ΔE in the table, PTS=97%, qualified, generally the PTS of new electrodes is ≥ 97%, and the electrodes that have been used for a long time can be relaxed, but generally PTS ≥ 95%, unless the test accuracy requirements are very low.
(3) Clean the electrode and then insert pH4.00 buffer solution, compare the reading with the data in step (1), the error should be ≤±2mV, otherwise it means that the repeatability of the electrode is poor.
⑷The test reading of the electrode should be stable within 30-60 seconds, otherwise it means that the electrode response is too slow
