How much does temperature affect pH accuracy measurement?
For pH electrodes, temperature affects each pH value of 0.003 pH/℃. For example, a pH meter of 0.2 level is calibrated in a 30 ℃ pH buffer and then tested for a solution at 60 ℃ (assuming the pH range of the solution is between pH 6 and 8 and pH 7.00, with a difference of one pH unit). The maximum error in temperature effect is 30 × 0.003=0.09pH. If it is 3 pH units (within the range of pH 4-10), the maximum error is 0.27 pH, which shows that temperature has a significant impact on pH. Of course, we can also draw a conclusion from it that in order to reduce the error of temperature in pH measurement, we should pay attention to the following three points:
(1) Try to choose a buffer solution that is close to the pH value of the measured solution to calibrate the pH meter.
(2) Try to make the temperature of the calibration solution consistent or close to the temperature of the measured solution.
(3) A pH meter with temperature compensation should be selected.
PH meters with an accuracy higher than 0.1 pH have temperature compensation adjustment, while pH meters with a 0.2 level do not have temperature compensation. Some pH meters with a 0.2 level accuracy are also claimed to have a 0.1 level accuracy, but this is actually impossible. Some people have confused the concepts of resolution 0.1pH and accuracy 0.1pH. Even in one pH unit, the pH error at a distance of 60 ℃ is 0.003 × 60=0.18pH, therefore, a pH meter without temperature compensation has the highest accuracy of only 0.2pH.
