How to identify a pH meter malfunction?
1. Check instrument function
(1) Check if the pH meter display screen shows degrees. If it does not display degrees, check if the power supply is normal. The inspection of Sedoris PB-10 is as follows: If the input signal exceeds the measurement range, the instrument will display - -. At this point, check whether the electrode is immersed in the solution. If it is determined that there is a problem with the electrode response, the instrument displays Error. When the efficiency of the motor is less than 90% or greater than 105% during calibration, this error will also be displayed, indicating that there is a problem with the electrode or buffer.
(2) Switch the instrument to mv mode and insert the shorts plug into the PH input port to check the potential. The reading of the Mettler pH meter is 0 ± 2mv, and the reading of the Sartorius pH meter is 0 ± 0.3mv
(3) Using a pH simulator and checking the potentials at pH 4.01/7.00/9.21, approximately+180mv, 0mv, and -130mv were obtained.
2. Check the function and use of electrodes
(1) Measure the potentials of buffer solutions 4.01 and 7.00 at room temperature. We should obtain 180mv ± 30mv and 0mv ± 30mv respectively
(2) If there is an ATC, measure the temperature of the ice water and display a reading of 0 ± 1 ℃. If the signal remains unchanged, there is a problem with the temperature probe.
(3) Replace the cable and remake the above steps. If 1&2 is successful, there is a problem with the cable. If 1 is not successful, there is a problem with the electrode or cable.
3. Check electrode performance
(1) Calibrate the electrode according to the instrument operation manual, and the zero point and slope values obtained should meet the technical specifications of the electrode. Zero point: 0mv ± 30mv, slope: 25 ℃, should be 95% -100%
(2) Check the response time of the electrode, immerse it in another pH buffer and stir it. After 30 seconds, check the potential of the electrode, and the change in the subsequent 30 seconds should not exceed 2mv.
4. How to store PH electrodes
It is best to keep the electrode storage solution consistent with the filling solution, for example, the consistent filling solution is in a 3mol/L KCL solution; If the filling liquid is in a KCL saturated AgCL solution of 3mol/L. Electrodes should not be left dry or immersed in distilled water for a long time, as this will shorten the electrode life.
5. What should be done when the electrode glass film dries up?
A glass film that has dried up for a short time can be restored to its function by soaking it in 0.1mol/L dilute hydrochloric acid for several hours, and a glass film that has dried up for a long time may not be restored using this method (Mettler)
The electrode should be kept in standard solution or KCL solution for at least 24 hours before the first use or when the electrode filling solution is dry (Sedolis)
