What should be paid attention to when measuring with pH meter sensor?
Before operation, check the integrity of the electrode first. At present, most of the electrodes used in pH meters are composite electrodes, while the old generation of pH meters still use glass electrodes and calomel electrodes. Because the composite electrode is widely used, the composite electrode is mainly discussed below.
At present, there are mainly two kinds of composite electrodes used in the laboratory: fully enclosed and non-enclosed, and the fully enclosed ones are relatively few, mainly produced by foreign enterprises. Before using the composite electrode, first check whether the glass bulb is cracked or broken. If not, it is generally considered that it can be used when the positioning and slope buttons can be adjusted to the corresponding pH value when two-point calibration is carried out with pH buffer solution, otherwise, the electrode can be activated according to the instruction manual. The activation method is to soak in 4% hydrogen fluoride solution for about 3 ~ 5 s, take it out and rinse it with distilled water, then soak it in 0.1mol/L hydrochloric acid solution for several hours, then rinse it with distilled water, and then calibrate it, that is, locate it with a buffer solution with a pH of 6.86(25℃). After adjustment, arbitrarily select another pH buffer solution to adjust the slope. If it cannot be adjusted, the electrode needs to be replaced. For the unsealed composite electrode, an external reference solution, namely 3 mol/L potassium chloride solution, should be added, so it is necessary to check whether the potassium chloride solution in the electrode is more than 1/3, and if not, 3 mol/L potassium chloride solution should be added. If the potassium chloride solution exceeds the position of the small hole, shake off the excess potassium chloride solution to make the solution below the small hole, and check whether there are bubbles in the solution. If there are bubbles, flick the electrode to drive them out completely.
