How to Tell If Your pH Meter Is Correct
There are many users who have doubts when using the pH meter. Is this pH meter accurate? Some people judge by work experience, some judge by pH test paper, and some judge by the pH meter used in the past. are unreliable. In fact, the safest, most reliable and simplest method is to use pH standard buffer solution for verification. This is the verification standard. Take three standard buffer solutions: pH6.86, pH4.00, pH9.18, preferably freshly prepared and at the same temperature, use pH6.86 for positioning calibration, pH4.00 for slope calibration, and then test pH9.18, pH Whether the calculation is accurate and whether it is qualified can be known immediately. If the accuracy is unqualified, you can further judge whether there is a problem with the pH meter or the pH electrode. Since the detection of pH meter requires corresponding equipment and technical methods, we can use the method in Article 23 of this book to detect the quality of the pH electrode, that is, we can determine whether it is a new pH electrode or send the pH meter repair.
Why must the pH electrode be soaked before use?
The pH electrode must be soaked before use, because the pH bulb is a special glass membrane, and there is a thin layer of hydrated gel on the surface of the glass membrane. H+ in solution has a stable good response. If the immersion is not sufficient, the response value will be unstable and drift during measurement. The soaking time is generally more than 24 hours.
For pH single glass electrode, it can be soaked in distilled water or 3.0N KCL solution, while single reference electrode can only be soaked in 3.0N KCL solution. For the PH composite electrode, you can use desalted water or distilled water or 3.0N solution, if soaked for a long time, you must use 3.0N KCL solution. When using PH single glass electrodes before, everyone has been used to soaking in ionized water. If using PH composite electrodes, they are still soaked in deionized water for a long time, then this wrong soaking method will make: a pH electrode with good performance becomes Form an electrode with slow response and poor precision, and the longer the immersion time, the worse the performance, because after long immersion, the KCL concentration of the electrode reference system will be greatly reduced, and the liquid junction potential will increase and become unstable.
