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Chapter 4
Using the pH Channel
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38
Orion Star A220 Series Portable Meter User Manual
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Testing a pH Electrode for Automatic Buffer Recognition
Use the following procedure to verify that the raw mV reading of the pH electrode is within one
pH unit (±59 mV) from the theoretical mV reading of the pH buffer, and therefore verify that the
pH electrode in use is capable of performing automatic buffer recognition.
1. Prepare the pH electrode according to the electrode manual. Set the meter measurement
mode to mV.
2. Rinse the pH electrode with distilled water, blot it dry with a lint-free tissue and place the
pH electrode into a pH 4.01 buffer at approximately 25 °C.
3. Wait for the measurement to stabilize and record the mV value of the pH 4.01 buffer when
the measurement is stable.
4. Remove the pH electrode from the pH 4.01 buffer.
5. Rinse the pH electrode with distilled water, blot it dry with a lint-free tissue and place the
pH electrode into a pH 7.00 buffer at approximately 25 °C.
6. Wait for the measurement to stabilize and record the mV value of the pH 7.00 buffer when
the measurement is stable.
7. The mV reading of the pH electrode in pH 4 buffer should be +117 to +236 mV and in pH 7
buffer should be -59 to +59 mV. If the mV readings are in the correct ranges, the pH
electrode is capable of performing automatic buffer recognition. If the mV readings are not
in the correct ranges, manually enter the pH buffer values during a pH calibration.
Thermo Scientific
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