Problems Needing Attention in Measuring PH Meters

Before proceeding, the integrity of the electrode should be checked first. Most of the electrodes used in the current pH meter (PH meter) are composite electrodes. The old generation pH meter is still using glass electrodes and calomel electrodes. Since the composite electrode is widely used, the following mainly discusses the composite electrode.

At present, the composite electrodes used in the laboratory are mainly closed and non-enclosed, and there are few fully-closed electrodes, mainly based on the production of foreign companies. Before using the composite electrode, check whether the glass bulb is cracked or broken. If not, use pH buffer solution for two-point calibration. When the positioning and slope buttons can be adjusted to the corresponding pH value, they are generally considered to be usable. Otherwise, they can be used. The instruction manual carries out electrode activation treatment. The activation method is immersed in 4% hydrogen fluoride solution for about 3 ~ 5s, removed and washed with distilled water, and then soaked in 0.1mol/L hydrochloric acid solution for several hours, rinsed with distilled water, and then calibrated, that is, with the pH value The 6.86 (25°C) buffer solution was positioned. After adjustment, another pH buffer solution was arbitrarily selected for slope adjustment. If it cannot be adjusted, the electrodes must be replaced. Non-enclosed type composite electrode, it is necessary to add an external reference solution that is 3mol/L potassium chloride solution, so you must check whether the potassium chloride solution in the electrode is more than 1/3, if not, add 3mol/L chlorination Potassium solution. If the solution of potassium chloride exceeds the position of the small hole, remove excess potassium chloride solution so that the solution is located under the hole and check for bubbles in the solution. If there is a bubble, the electrode is to be lightly pushed out and the bubble is completely expelled.

During use, the rubber on the electrode should be peeled off to expose the small hole. Otherwise, during the analysis, a negative pressure will be generated. As a result, the potassium chloride solution will not be able to exchange ions through the glass bulb with the tested solution. Will make the measurement data inaccurate. After the measurement is completed, the eraser should be restored to seal the hole. After cleaning the electrode with distilled water, it should be immersed in 3mol/L potassium chloride solution to keep the electrode bulb moist. If the protective solution is found to have lost before use, it should be soaked in 3mol/L potassium chloride solution for several hours. So that the electrode reaches the best measurement state. In actual use, some analysts found that some analysts treated the composite electrode as a glass electrode and dipped it in distilled water for a long time. This was incorrect. This caused the concentration of potassium chloride solution in the composite electrode to be greatly reduced. In the measurement, the electrode reaction is insensitive, resulting in inaccurate measurement data. Therefore, the composite electrode should not be soaked in distilled water for a long time.