Summary of Reasons for the Instability of pH Meter Numbers
① Check if the electrode is damaged.
② It should be that the electrode has been used for too long. First, calibrate it to see if it is effective.
③ You can try soaking the probe in 2.5mmoL/L KCL solution.
④ Clean the glass ball. Has it been too long and there are some organic substances attached to it, causing the reaction to be insensitive.
⑤ There is a chemical equilibrium CO2+H2O → H++HCO3- in water, and due to the weak alkalinity of general pure or surface water, the equilibrium shifts towards a positive reaction direction, resulting in a continuous increase in pH.
⑥ Add neutral salt (such as KCL) into the tested water sample as a Ionic strength regulator to change the total ionic strength in the solution, increase conductivity, and make the measurement fast and stable. This method is stipulated in the national standard GB/T6P04.3-93: "In order to reduce the impact of liquid junction potential and quickly reach stability when measuring water samples, a drop of neutral 0.1mol/LKCL solution is added to every 50ml of water samples." Although this method changes the Ionic strength in the water samples, causing the pH value to change to a certain extent, the experiment shows that this change only changes about 0.01pH in value, which is completely acceptable. But when using this method, it is important to note that the KCL solution added should not contain any alkaline or acidic impurities. Therefore, KCL reagents should be of high purity, and the water quality of the prepared solution should also be of high purity neutral water quality.
How long is the lifespan of pH electrodes?
The lifespan of pH electrodes is related to the properties of the measured sample, sample temperature, frequency of use, and maintenance status. Under normal use and proper maintenance, the pH electrode has a lifespan of 1 to 2 years.
Is the pH meter accurate?
Is the pH meter accurate? The only reliable and simplest method is to use pH standard buffer solution for calibration. Take three pH standard buffer solutions: pH 6.86, pH 4.00, pH 9.18 (preferably freshly prepared and at the same temperature), perform positioning calibration with pH 6.86, slope calibration with pH 4.00, and then test pH 9.18 to see if the pH meter is accurate and qualified. If the accuracy is not qualified, it can be further determined whether there is a problem with the pH meter or the pH electrode
