What to pay attention to when measuring with an acidity meter sensor
Before performing the operation, the integrity of the electrodes should be checked first. At present, most of the electrodes used in pH meters are composite electrodes, while the older generation of pH meters still use glass electrodes and calomel electrodes. Due to the widespread use of composite electrodes, the following mainly discusses composite electrodes.
At present, there are mainly two types of composite electrodes used in laboratories: fully enclosed and non enclosed. Fully enclosed electrodes are relatively rare and mainly produced by foreign enterprises. Before using the composite electrode, first check whether there are cracks or breakage in the glass bulb. If not, perform two-point calibration with pH buffer solution. When the positioning and slope buttons can be adjusted to the corresponding pH value, it is generally considered to be usable. Otherwise, follow the instructions for electrode activation treatment. The activation method is to soak in a 4% hydrogen fluoride solution for about 3-5 seconds, then take it out and rinse it with distilled water. After soaking it in a 0.1mol/L hydrochloric acid solution for several hours, rinse it clean with distilled water, and then calibrate it. That is, use a buffer solution with a pH value of 6.86 (25 ℃) for positioning. After adjustment, choose another pH buffer solution for slope adjustment. If it cannot be adjusted, replace the electrode. For non enclosed composite electrodes, an external reference solution of 3 mol/L potassium chloride solution needs to be added inside. Therefore, it is necessary to check whether the potassium chloride solution in the electrode is above 1/3. If not, 3 mol/L potassium chloride solution needs to be added. If the potassium chloride solution exceeds the position of the small hole, discard the excess potassium chloride solution and place it below the small hole. Check for any bubbles in the solution, and if there are bubbles, gently tap the electrode to completely remove them.
