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Star Republic: Guide for Biologists

pH meter

Different models of pH meter may have different procedures. The instructions below are general principles.

Calibration

1. If the pH meter has not been used for a few days, it needs to be calibrated.

2. Turn on the power, and change to Calibration Mode.

3. Rinse the electrode with deionized water, and blot dry with a kimwipe. Turn cap ring to open the fill hole.

4. Place probe in pH standard buffers. Common standard buffers are pH 7.0, pH 4.0, and pH 10.0. You may calibrate with one buffer or two buffers on some models of pH meter. Chose the ones whose pH is nearer to your sample pH.

Don't place probe in the standard stock bottle. Take a small aliquot in a tube and replace after a few uses.

5. If room temperature is not 25 C, you may need to adjust for temperature.

6. Rinse the electrode with deionized water, and blot dry with a kimwipe. Place the electrode in a sample or the storage buffer (saturated KCl).

Measurement

7. Turn on the power, and mode to PH.

8. Place the pH electrode in a small amount of the sample.

Never place the pH electrode in a vessel with a magnetic stir bar or other stirring device. The stir bar could accidentally break the pH electrode.

Make sure the fill hole is open. Wait until the reading stabilized.

9. Rinse the electrode with deionized water, and blot dry with a kimwipe. Place the electrode in the storage buffer (saturated KCl).