Discussion on the influence of temperature on pH measurement accuracy
For pH electrodes, the influence of temperature is 0.003 pH/℃ for each pH, for example, a 0.2-level pH meter is calibrated in a buffer solution of pH 7.00 at 30℃, and then the solution at 60℃ is tested (assuming that the pH range of the solution is between pH 6 and 8 and pH 7.0 is different by one pH unit), then the maximum error of temperature influence is 30×0.003=0.09 pH If it is 3 pH units (in the range of pH 4~10), the maximum error is 0.27 pH, from which it can be seen that the influence of temperature on pH is very real. Of course, we can also draw the conclusion that in order to reduce the error of temperature on pH measurement, we should pay attention to the following three points:
(a) Try to select a buffer solution close to the pH value of the tested solution to calibrate the pH meter;
(b) Try to make the temperature of the calibration solution consistent with or close to the temperature of the measured solution;
(c) A pH meter with temperature compensation should be selected.
All pH meters with accuracy higher than 0.1 pH have temperature compensation adjustment, while pH meters with grade 0.2 have no temperature compensation. Some 0.2-level pH meters also claim to have 0.1-level accuracy, which is actually impossible. Some people confuse the two concepts of resolution 0.1 pH and accuracy 0.1 pH.. Even in a pH unit, the pH error at 60℃ is 0.03× 60 = 0.18 pH. Therefore, the highest accuracy of a pH meter without temperature compensation is only 0.2 pH.
