PH meter measurement points

- Feb 26, 2018-

Before proceeding, first check the integrity of the electrode. Calomel electrode. Since the composite electrode is widely used, the following mainly discusses the composite electrode.

Laboratory use of composite electrodes are mainly closed and non-closed two, fully enclosed less, mainly based on the production of foreign enterprises. Composite electrode First check the glass bulb for cracks, broken, if not, with the pH buffer solution for two-point calibration, positioning and slope buttons can be adjusted to the corresponding pH value, the general that can be used, or can press Manual for electrode activation. Activation method is immersed in 4% hydrogen fluoride solution about 3 ~ 5 s, washed with distilled water was removed, and then soaked in 0.1mol / L hydrochloric acid solution for several hours, rinsed with distilled water, and then calibrated, that is, with a pH value For 6.86 (25 ℃) buffer solution for positioning, adjusted to arbitrarily choose another pH buffer solution for slope adjustment, if not adjusted to, you need to replace the electrode. Non-enclosed composite electrode, which should be added to the external reference solution that 3 mol / L potassium chloride solution, it is necessary to check the electrode in the potassium chloride solution is more than 1/3, if not, to add 3 mol / L Potassium chloride solution. If the potassium chloride solution beyond the hole position, the excess potassium chloride solution dumped, the solution is located in the hole below, and check whether there is air bubbles in the solution, such as bubbles to flick the electrode, the bubble completely out.

In the process of using the rubber should be stripped above the electrode, the hole exposed outside, or in the analysis, will produce negative pressure, resulting in potassium chloride solution can not be successfully passed through the glass bulb with the test solution for ion exchange, Will make the measurement data inaccurate. The rubber should be restored after the measurement is completed, seal the hole. After the electrode is washed with distilled water, it should be soaked in 3 mol / L potassium chloride solution to keep the electrode bulb wet. If the protective solution has been found to be lost before the electrode is used, it should be immersed in 3 mol / L potassium chloride solution A few hours, so that the electrode to achieve the best measurement state. In actual use, it was found that some analysts treat the composite electrode as a glass electrode and soak it in distilled water for an extended period of time, which is not correct, which greatly reduces the concentration of potassium chloride solution in the composite electrode, resulting in Electrode reaction is not sensitive in the measurement, eventually leading to inaccurate measurement data, so the composite electrode should not be immersed in distilled water for a long time.

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