What is the effect of temperature on the accuracy of pH measurements?
For pH electrodes, the temperature affects each pH by 0.003 pH/°C. For example, a 0.2-level pH meter is calibrated in a 30°C pH buffer, and then tested at a 60°C solution (assuming that the pH range of the solution is between pH 6 and 8 differs from pH7.00 by one pH unit), then the maximum error affected by temperature is 30×0.003=0.09pH. If it is 3 pH units (in the range of pH 4 to 10), the maximum error is 0.27pH. It can be seen from this that temperature has a great impact on pH. Of course, we can also conclude from this that in order to reduce the error of temperature on 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 solution being measured to calibrate the pH meter.
(2) Try to make the temperature of the calibration solution consistent with 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 0.1pH have temperature compensation adjustment, while pH meters with level 0.2 do not have temperature compensation. Some 0.2-level pH meters also claim to have 0.1-level accuracy. In fact, this is impossible. Some people confuse the two concepts of resolution 0.1pH and accuracy 0.1pH. Even in terms of one pH unit, the pH error at 60°C is 0.003×60=0.18pH. Therefore, the highest accuracy of a pH meter without temperature compensation is only 0.2pH.
