Factors affecting the measurement error of online pH meter
pH meter is one of the common electrochemical analysis instruments in chemical laboratories. However, users are prone to large errors and failures during use. The following are summarized factors that affect the measurement error of online pH meters:
1. Inspection of online pH meter
When laboratory personnel use a pH meter to measure the pH value of a solution, if they do not trust the measured results, they can use the following method to judge, that is, measure one or two pHs standard solutions. If the error of the measured pHs standard solution is very small, it means that the measurement results of the pH acidity meter are reliable. On the contrary, if the error in measuring the pHs standard solution is very large, it means that there is something wrong with the electric meter, pH electrode and pHs standard solution in the pH acidimeter. Check them one by one according to the following method.
(1) For electric meters, except for obvious faults, issues that should be paid attention to: first, the temperature compensator must be positioned accurately, and the knob must not be loose; second, for a pH meter with slope correction, when measuring the solution using the one-point positioning method , the slope should be placed at the 100% position; third, pay attention to whether the glass ph electrode jack is in good contact.
(2) For the pH glass electrode in an electrode, check whether the silver-silver chloride internal reference electrode is immersed in the solution inside the glass electrode. For calomel electrodes, attention should be paid to whether there are bubbles in the tube, whether the salt bridge is blocked, and whether the calomel electrode contact piece is oxidized. You can also use good pH electrodes to judge by replacing them one by one.
(3) The pH meter pHs standard solution should be prepared again, or a calibrated pH acidity meter can be used to measure the error of the standard solution. Under normal circumstances, the possibility of large errors in the pHs standard solution is small.
