Summary of causes of unstable pH meter numbers:
① Check whether the electrode is damaged.
② It should be that the electrode has been used for too long. Calibrate it first to see if it is effective.
③ You can try soaking the probe in 2.5mmoL/L KCL solution.
④Clean the glass ball. It has been a long time and some organic matter has been attached to it, causing the reaction to be insensitive.
⑤ There is a chemical equilibrium CO2 + H2O → H+ + HCO3- in water. Since ordinary pure water or surface water is weakly alkaline, the balance moves in the direction of the positive reaction, so the pH will keep rising.
⑥ Add neutral salt (such as KCL) as an ionic strength regulator to the water sample to be measured to change the total ionic strength in the solution, increase the conductivity, and make the measurement fast and stable. The national standard GB/T6P04.3-93 for this method stipulates: "In order to reduce the influence of the liquid junction potential and quickly reach stability when measuring water samples, add a drop of neutral 0.1moL/LKCL solution to every 50ml water sample." Although this method Changing the ionic strength in the water sample will cause its pH value to change to a certain extent, but experiments have proven that this change only changes the value by about 0.01pH, which is completely acceptable. However, when using this method, it must be noted that the KCL solution added should not contain any alkaline or acidic impurities. Therefore, the KCL reagent must be of high purity, and the water quality of the prepared solution must also be high-purity neutral water.
How long is the life of a pH electrode?
The life of the pH electrode is related to the properties of the measured sample, sample temperature, frequency of use, and maintenance. Under normal use and proper maintenance, the life of a pH electrode is 1 to 2 years.
Is the pH meter accurate?
Is the pH meter accurate? The only reliable and simplest method is to use a pH standard buffer solution for verification. Take three pH standard buffer solutions: pH6.86, pH4.00, pH9.18 (preferably freshly prepared and at the same temperature), perform positioning calibration with pH6.86, slope calibration with pH4.00, and then test pH9. 18 Check whether the pH meter is accurate and you will know immediately whether it is qualified or not. If the accuracy is not up to standard, you can further determine whether there is a problem with the pH meter or the pH electrode.
