Two-point calibration of pH meter
For precision pH meters, in addition to ¨ positioning ¨ and ¨ temperature compensation ¨ adjustment, it also has electrode ¨ slope ¨ adjustment, which needs to be calibrated with two standard buffers. Generally, first perform ¨positioning¨ calibration with pH6.86 or pH7.00, and then select pH4.00 (acidic) or pH9.18 and pHI0.0l according to the acid-base condition of the test solution.
(Alkaline) buffer solution for ¨slope¨ correction. The specific operation steps are:
(1) The electrode is washed and dried, immersed in a pH6.86 or pH7.00 standard solution, and the temperature compensation knob of the instrument is placed at the solution temperature. After the displayed value is stable, adjust the positioning knob so that the displayed value of the instrument is the pHs value of the standard solution.
(2) Take out the electrode, wash it, spin dry, and immerse it in the second standard solution. After the displayed value is stable, adjust the slope knob of the instrument so that the displayed value of the instrument is the pHs value of the second standard solution.
(3) Take out the electrode, wash it, spin dry, and then immerse it in pH6.86 or pH7.00 buffer solution. If the error exceeds 0.02pH, repeat steps (1) and (2) until the correct pHs can be displayed without adjusting the knob in the two standard solutions.
(4) Take out the electrode and spin it dry, adjust the pH temperature compensation knob to the temperature of the sample solution, immerse the electrode in the sample solution, shake it and place it at rest, and display a stable reading.
