Two-point calibration of pH testers
For precision pH meters, in addition to positioning and temperature compensation adjustment, there is also electrode slope adjustment, so two buffers are required for calibration. Generally, start the positioning (calibration) with pH6.86 or pH7.00, and then start the slope (calibration) with pH4.00 (acidic) or pH9.18 and pHI0.0l (alkaline) buffer according to the pH of the test solution.
Second, the actual operation steps are as follows:
(1) Wash and dry the electrode, soak it in the reference solution of pH 6.86 or pH 7.00, and set the temperature compensation knob of the instrument to the temperature of the solution. After the indicated value is stable, adjust the positioning knob so that the indicated value of the instrument is the pHs value of the specification solution.
(2) Take out the electrode, wash it, spin dry, and soak it in the solution of the second specification. After the indicated value is stable, adjust the slope knob of the instrument so that the indicated value of the instrument is the pHs value of the second standard solution.
(3) Take out the electrode, wash it, spin it dry, and then soak it in a buffer solution of pH 6.86 or pH 7.00. If the error exceeds 0.02 pH, repeat steps (1) and (2) until it can be adjusted without adjusting the knob. Correct pHs are shown in both standard solutions.
(4) Take out the electrode and spin it dry, adjust the pH temperature compensation knob to the temperature of the sample solution, soak the electrode in the sample solution, swing it, and then let it stand until the reading is stable.
