A component of the pH meter, a pH probe contains an electrode which is used to sense the concentration of hydrogen ions in chemical solutions. They are used in scientific, medical, diagnostic and engineering laboratories, as well as by gardeners and food manufacturers. Learning how to use a pH probe will allow you to test and correct the pH of any solution.
- Skill level:
Things you need
- Digital pH meter
- Solution to be pH-tested
- Rubber bulbs
- Disposable plastic droppers or washable glass droppers
- Magnetic stirrer and magnetic stirring plate
- Chemical or fume bonnet
- Diluent or solvent
- PH standard solutions (pH 4, 7, 10)
- Laboratory-grade distilled water
- Clear glass or plastic beakers
- Laboratory-grade cleaning wipes
Learn the different components and functions of your particular model of pH meter by reading through the manufacturer's instructions. Some meters are portable or hand-held, while others are supplied with an immobile base. Immobile meters should not be used outside an enclosed room (e.g., a laboratory), while portable meters will be difficult to manipulate if you need to modify and stir your solutions; therefore, ensure you are using the appropriate type of meter.
Locate the power and function buttons. To use a pH probe, the key buttons are the "Standby," "Calibrate" or "Standardize," and "Measure" buttons. This may differ depending on your model or manufacturer. Switch the meter on and set it to "Standby."
Make small aliquots of pH standardisation solutions at pH4, pH7 and pH10. These are normally obtained from commercial chemical suppliers. Generally, only a small volume is required to cover the tip of the electrode (about 2 inches high), and this should be poured into a small beaker with a wide mouth to allow insertion of the probe.
Remove the probe from the "soak solution" it is being stored in. Make sure this solution is not contaminated while the meter is being used. Rinse the length and tip of the probe in distilled water and let this flow into a waste-collection beaker. Rinse for at least half a minute to remove all salt crystals, dust or debris.
Calibrate the probe. Switch the meter to "Standardize" or "Calibrate" and then submerge the probe into one of the pH standard solutions (e.g., pH 7), making sure that the electrode-containing probe tip is completely covered by the solution. Allow the meter reading to stabilise and then rinse the probe thoroughly with distilled water. Repeat this with the other standardisation solutions. Once the meter is calibrated for all three pH levels, it is ready to use.
Switch the meter from "Standardize" or "Calibrate" to "Measure" to begin using the pH probe. Rinse the tip of the probe in distilled water and then soak it in the solution to be tested. Wait for the readings to stop fluctuating. Once the numbers have stabilised, record this to one or two decimal places.
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