1. Use fresh buffer
2. Open the electrode protective sleeve
3. Measure the gap and rinse the electrode with deionized water
4. Stir the buffer and sample: a) Always stir at the same rate; b) Stir first, then measure
5. When preparing the pH electrode, rinse the electrode with distilled water before and after the measurement. Use a linen-free cloth to absorb excess water from the electrode tip to avoid rubbing the electrode bulb, otherwise static electricity will be generated and interfere with the accurate measurement of pH.
6. Make sure that the buffer temperature is the same as the sample temperature. If the sample temperature is different, use a temperature compensation probe for temperature compensation.
7. Regularly check the electrode slope with the two-point calibration method. When the electrode reading drifts or the slope is lower than 92%, please refer to electrode cleaning to clean the electrode.
Third, maintenance of the electrode
1. Electrode cleaning
Universal cleaning solution-Immerse the electrode in 0.1M HCl or 0.1M HNO3 solution for 15 minutes, then immerse the electrode in the electrode storage solution for 30 minutes.
2. Liquid junction blockage (salt precipitation)
Causes: hard water, mud, organic dirt, planktonic microorganisms, moss, etc. Attached to the seepage sand core around the bulb and PTFE, the external reference electrode cannot work normally.
Solution: Immerse the electrode (60°C) in hot water for 15-20 minutes; soak the electrode in a hot saturated KCl (60°C) solution for 20-30 minutes and cool to room temperature; soak the electrode in a pH 4 buffer solution for 20 to 30 minutes 30 minutes.
Check for excessive crystals. If so, rinse the crystals repeatedly with deionized water to check whether the flow rate is normal
If not, soak the electrode (60°C) for 15-20 minutes in hot water; soak the electrode in a hot saturated KCl (60°C) solution for 20-30 minutes and cool to room temperature; soak the electrode in pH 4 buffer 30 minutes. Immerse the electrode tip in concentrated HCl for 5-10 minutes, rinse the electrode, and check whether the electrolyte flow rate is normal. If the liquid junction is still blocked, pull the liquid junction (do not touch the glass bulb)
4. Precipitation of inorganic substances on the pH sensitive membrane
Cause: Measurement of inorganic samples
Solution: clean with EDTA, ammonia or acid
5. Dehydration of pH sensitive membrane
Causes: Improper storage, long-term use, high temperature operation or strong alkaline solution, resulting in slow and unstable response
Solution: Activate the electrode
Immerse the electrode in 0.1 M HCl for 1 minute, rinse with tap water for 30 seconds, soak the electrode in 0.1 M KOH for 1 minute, rinse with tap water for 30 seconds, calibrate the test electrode with buffer, if it still does not work, repeat the above steps, up to 3 times
6. The PH electrode is used for a long time, and the necessary cleaning and maintenance of the electrode are not used correctly in the tested environment, which results in unstable electrode data and other factors. Solution: After the electrode is used for 2-3 months, perform a bulb cleaning on the electrode and an inspection on the liquid contact part. Solution: Take the electrode out of the use environment to see if there is dirt on the surface of the bulb. If there is, you can wipe it with ethanol cotton lightly, and then clean it with deionized water.
[Note that the bulb is fragile, you should pay attention to the process of wiping]. Then check the liquid contact part to see if there are contaminants attached to the surface. If there is, you can use deionization to rinse. You can also shake the electrode back and forth in the measuring cup. If the water quality is not clean, change the water until the dirt disappears. . Then wash the electrode and place it in the activation solution for 8 hours, then measure it in the standard solution to restore it to the measurement state.
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