What is one-point calibration of pH meter
Any pH meter must be calibrated by the pH standard solution before measuring the pH value of the sample. For samples whose measurement accuracy is below 0.1PH, the instrument can be adjusted by a point calibration method. Generally, the pH6.86 or pH7.00 standard is used. buffer solution. Some instruments are only 0.2PH or 0.1PH, so the instrument only has one positioning adjustment knob. The specific operation steps are as follows:
(1) Measure the temperature of the standard buffer solution, and check the table to determine the PHS value at this temperature. Adjust the temperature compensation knob to this temperature.
(2) Rinse the electrode with pure water and dry it.
(3) Dip the electrode into the buffer solution and shake it and place it still. After the reading is stable, adjust the positioning knob to make the instrument display the PHS value of the standard solution.
(4) Take out the electrode, rinse and dry it.
(5) Measure the temperature of the sample, and adjust the pH meter temperature compensation knob to the temperature value.
(6) Dip the electrode into the sample solution, shake it and place it still, and display a stable reading.
Use and maintenance of pH meter electrodes
There are two electrodes on the pH meter, a calomel reference electrode and a glass electrode.
The calomel electrode is used as a reference electrode, and it is filled with a saturated KCl solution, which should contain a small amount of KCl crystals, and keep the liquid level covering the calomel column (filled to the bend of the glass tube). The small rubber plug on the side branch must be removed during use, otherwise the ion exchange function of the salt bridge cannot be achieved. When not in use, the small rubber plug and the end rubber cap should be covered.
The glass electrode is used as a pH indicating electrode and should be used within the validity period.
When the new electrode is not used for a long time, it should be soaked in pure water for at least 24 hours before use. If you need to use it frequently, rinse it and soak it in pure water after use. If you don’t use it for a long time, take it out after soaking, dry it with filter paper, and store it in a box. The electrodes should be clean and free from oil, mildew and scars.
