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General pH Calibration Procedures
The standard procedure is to select two buffers that bracket the expected sample pH. More buffers can be used for greater accuracy over a wider pH range. For best accuracy, use buffers that are no more than 3pH units apart. Consult your pH meter manual for specific details on operating your meter.
- Remove the electrode from its storage solution and rinse it with distilled water.
- Dab the electrode with tissue paper to remove excess water (do not rub!).
- Place the electrode into the first buffer (usually pH7).
- Wait for a stable reading.
- Orion meters will automatically recognise the pH buffer and give the temperature corrected value.
- Rinse the electrode as before and place in the second buffer. Wait for a stable reading.
- The meter will read the temperature corrected value of the second buffer.
- Rinse the electrode as before. Place the electrode in your sample and wait for a stable reading.Record the pH and temperature of your sample.
Successful Calibration & Measurement
- Always use fresh pH buffers.
- The electrode calibration should be 95-102%.
- Remove the electrode filling solution cover when measuring to ensure a uniform flow of filling solution.
- Between measurements, rinse the electrode with distilled water and then with the next sample to be measured.
- Stir all buffers and samples consistently, either a) stir continuously (at the same rate) whilst taking a measurement or b) stir your buffer or sample, stop, and then take a measurement.
- Place some insulating material between your stirrer and your sample to prevent heating of your sample.
- Avoid rubbing or wiping the electrode bulb.
- Store your pH electrode properly. pH7 buffer is fine, pH7 buffer with added KCI is better, pH storage solution is best.
Caution: Do not store your pH electrode in distilled water.
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