Influence of Temperature on pH Measurement Accuracy
For pH electrodes, the effect of temperature is 0.003pH/°C. For example, a 0.2-grade electrode is calibrated in a buffer solution of pH 7.00 at 30°C, and then the solution at 60°C is tested (assuming that the pH range of the solution is at pH6 There is a difference between pH7.00 and pH7.00 by one pH unit), then the maximum error caused by temperature is 30 x 0.003=0.09pH. If it is 3 pH units (in the range of pH 4-10), the maximum error is 0.27pH, from which it can be seen that the temperature has a great influence on pH. Of course, we can also draw conclusions from it. In order to reduce the error of temperature to 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 solution to be measured to calibrate the pH meter.
(b) Try to make the temperature of the calibration solution the same or close to the temperature of the measured solution.
(c) A pH meter with temperature compensation should be selected.
pH meters with an accuracy higher than 0.1pH have temperature compensation adjustments, while pH meters with a grade of 0.2 do not have temperature compensation. Some 0.2-grade pH meters also claim to have 0.1-grade accuracy. In fact, this is impossible. Some people confuse the two concepts of resolution 0.lpH and precision 0.lpH. Even in terms of one pH unit, the pH error at a distance of 60°C is 0.003 x 60=0.18pH. Therefore, the highest accuracy of a pH meter without temperature compensation is only 0.2pH
