pH meter use check
1. General inspection method of glass electrode
(1) Check the zero potential
Set the pH meter to the "mV" measurement position, insert the glass electrode and the reference electrode together into the buffer solution with pH=6.86, the reading of the instrument should be about -50~50mV.
(2) Check the slope
Connect to (1), then measure the mV value of the buffer solution with pH=4.00 or pH=9.18, and calculate the slope of the electrode. The relative slope of the electrode should generally be compounded with technical indicators.
Note: 1) The electrode zero potential value check method is only for the glass electrode whose equipotential point is 7. If the equipotential point of the glass electrode is not 7, it will be different. 2) For some pH meters, if the calibration adjustment can meet the requirements, and the above inspection results are not out of range, the electrode can be used at will. 3) For some smart pH meters, you can directly refer to the zero potential and slope values obtained from the calibration results of the instrument.
2. Inspection method of reference electrode
(1) Internal resistance inspection method
A laboratory conductivity meter is used. One end of the electrode socket of the conductivity meter is connected to a reference electrode, and the other end is connected to a metal wire. The reference electrode and the metal wire are immersed in the solution at the same time. The measured internal resistance should be less than 10kΩ. If the internal resistance is too large, it means that the liquid junction is blocked and should be dealt with.
(2) Electrode potential inspection
Take a good reference electrode of the same model and the reference electrode to be tested and connect them to the input terminals of the pH meter, and then insert KCl solution (or buffer solution with pH=4.00) at the same time, and the measured potential difference should be -3 ~3mV, and the potential change should be less than ±1mV. Otherwise, the reference electrode should be replaced or regenerated.
(3) Visual inspection
The silver-silver chloride wire should be dark brown. If it is off-white, it means that the silver chloride has been partially dissolved.
