Calibration of pH meters ensures their accuracy and consistency.
A pH meter is used to measure the acidity or alkalinity (that is, the pH level) of chemical solutions, such as laboratory buffers used in research, reagents for gardening or even liquids in food processing and electrical manufacturing facilities. Learning adjust, or calibrate, a digital pH meter is a very basic scientific skill that allows you to ensure that a solution's pH is correct. Inaccurate or incorrect pH levels can damage equipment, kill plants and organisms, or cause severe illness.
Instructions
1. Put on proper safety gear, including laboratory coat, gloves, goggles and face mask. This is absolutely mandatory when handling chemicals or working with laboratory equipment.
2. Sterilize all equipment and tools. This prevents carryover contamination in any solutions that will be pH-tested and modified after the pH meter is calibrated. Autoclave all laboratory glassware, and use only sterile, distilled water.
3. Locate the probe, or electrode, on the digital pH meter. This measures the pH of a solution and must be calibrated. It contains a tip, which is always stored in an airtight container of "soak" solution.
4. Pull the electrode's tip gently out of the container.
5. Rinse the electrode's tip over a beaker using distilled water. Don't contaminate the soak buffer with this wash. Rinse the probe tip for at least 30 seconds, or until you are confident that no salt crystals or other debris are present on the probe.
6. Pour each pH standard solution into small beakers. Use just enough volume to submerge the tip of the electrode; usually 2 inches is sufficient.
7. Turn on the pH meter's power and switch its operation mode from "standby" to "standardize" (or the equivalent function on your model).
8. Soak the electrode tip in each standard in turn. Wait for the readings on the meter to stabilize to the pH of the standard being used. For example, to calibrate for pH 4, soak the electrode in pH 4 standard, and then wait until the reading stops fluctuating and is at 4.0. Rinse the electrode tip in distilled water over a beaker. Repeat for pH 7 and pH 10. The meter is now adjusted and ready to use.
Tags: distilled water, digital meter, each standard, over beaker, Rinse electrode