pH meter calibration

The pH meter is abbreviated as a pH meter and consists of an electrode and an electricity meter. If the electrode can be properly maintained during use, the standard buffer can be prepared as required and the electricity meter can be operated correctly, the pH indication error can be greatly reduced, thereby improving the reliability of the chemical experiment and medical test data.

First, the correct use and maintenance of electrodes The electrodes used in the laboratory are composite electrodes, its advantages are easy to use, without the impact of oxidizing or reducing substances, and the balance of faster. In use, the rubber sleeve and the rubber sleeve at the bottom of the electrode filling port are completely removed to maintain the hydraulic pressure difference of the potassium chloride solution in the electrode.

Here's a simple introduction to the use and maintenance of the electrode:

1. When the composite electrode is not used, it can be fully immersed in 3M potassium chloride solution. Never wash with wash solution or other absorbent agents.

2. Before use, check the bulb at the front of the glass electrode. Under normal conditions, the electrode should be transparent and free from cracks; the bulb should be filled with a solution and no bubbles should be present.

3. When measuring a solution with a large concentration, try to shorten the measurement time as much as possible and carefully clean it after use to prevent the measured liquid from adhering to the electrode and contaminating the electrode.

4. After cleaning the electrode, do not wipe the glass film with filter paper, but use filter paper to dry it to avoid damage to the glass film and prevent cross-contamination, affecting the measurement accuracy.

5. The silver-silver chloride internal reference electrode of the measurement electrode should be immersed in the chloride buffer solution in the bulb to avoid the phenomenon of digital chattering in the display part of the electricity meter. When using, pay attention to gently swing the electrode.

6. The electrode cannot be used for strong acids, alkalis or other corrosive solutions.

Second, the preparation and storage of standard buffer 1. The pH reference material should be stored in a dry place, such as mixed phosphate pH standard substance will occur when the humidity is high, deliquescence, once the deliquescence, the pH reference material can not be used.

2. The preparation of pH standard solution should use double distilled or deionized water. If you are using a 0.1 pH meter, use distilled water.

3. The pH standard solution should be diluted with a smaller beaker to reduce the pH standard solution on the beaker wall. Plastic bags or other containers for storage of the pH standard substance should be rinsed with distilled water several times in addition to the plastic bags or other containers, and then poured into the formulated pH standard solution to ensure that the prepared pH standard solution is accurate.

4. The prepared standard buffer solution can generally be stored for 2-3 months. If turbidity, mildew or sedimentation is found, it cannot be used.

5. Alkaline standard solution should be sealed in a polyethylene bottle. Prevent carbon dioxide from entering the standard solution to form carbonic acid and reduce its pH.

Third, the correct calibration of the pH meter pH meter due to the different types of electrical design and type, its operation steps are different, so the operation of the pH meter should be carried out in strict accordance with its instructions. The pH meter calibration method uses a two-point calibration method that selects two standard buffers: one is a pH 7 standard buffer, and the second is a pH 9 standard buffer or a pH 4 standard buffer. The pH meter standard buffer was used to locate the electricity meter, and a second standard buffer was selected according to the acidity and alkalinity of the solution to be tested. If the test solution is acidic, use pH4 standard buffer; if the test solution is alkaline, use pH9 standard buffer. If the pH meter is manually adjusted, it should be repeated several times between the two standard buffers until there is no need to adjust its zero and position (slope) knobs. The pH meter can accurately display the two standard buffer pH values. The calibration process ends. After this, the zero point and positioning knob should not be moved again during the measurement. If it is a smart pH meter, it does not need to be adjusted repeatedly, because the pH value of several standard buffers has been stored in the inside, and it can be automatically identified and automatically calibrated. But pay attention to the standard buffer selection and the accuracy of its preparation.