pH Standard Solution
pH is measured using a pH meter. A pH meter is a device consisting of a detecting section composed of a glass electrode and a reference electrode, an amplifying section to amplify the detected electromotive force, and an indicating section to indicate the measurement result.
According to the Japanese Pharmacopoeia, a pH meter should have a reproducibility within ± 0.05 for the indicated pH value when the pH of a given pH standard solution is repeatedly measured five times after the detecting section is washed thoroughly with water before each measurement.
Fujifilm Wako supplies pH standard solutions for the calibration of pH meters.
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How to calibrate pH meters
A pH meter is calibrated using two different pH standard solutions.
- Immerse the electrode in 163-12151 standard neutral phosphate solution (pH 6.86 at 25°C). Calibrate the pH meter by adjusting it to a value corresponding to the temperature of the pH standard solution using the zero calibration knob. After zero calibration, wash the electrode with pure water and gently wipe with filter paper, etc.
- Use a pH standard solution having a pH value covering the expected pH of the sample as the second standard solution, and measure its pH under similar conditions.
- How to choose a second standard
- ■ When the expected pH is acidic (pH ≤ 7)
166-12141 standard phthalate solution (pH 4.01, 25°C)
151-01845 standard oxalate solution (pH 1.68, 25°C) - ■ When the expected pH is alkaline (pH ≥ 7）
203-08771 standard borate solution (pH 9.18, 25°C)
037-16145 standard carbonate solution (pH 10.01, 25℃) - If the obtained pH does not coincide with the value corresponding to the temperature, use the span calibration knob to make it coincide with the specified pH. After span calibration, wash the electrode with pure water and gently wipe with filter paper, etc.
- Repeat similar procedures until the pH of the two pH standard solutions coincides with the specified pH value within ± 0.05, without any adjusting operation.
- If a device equipped with a temperature compensation knob is used, adjust the scale value to the temperature of the pH standard solution before calibration.
- If a device with automated calibration is used, it is necessary to periodically check that the pH of the two pH standard solutions coincides with the specified value within ± 0.05.
- The operation of pH meters is different for each pH meter. See the instructions for use of your pH meter.
For research use or further manufacturing use only. Not for use in diagnostic procedures.
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