How much do you know about the two-point calibration of pH meters?
For precision-grade pH meters, in addition to ¨positioning¨ and ¨temperature compensation¨ adjustments, there is also an electrode ¨slope¨ adjustment, which requires calibration with two standard buffers. Generally, pH 6.86 or pH 7.00 is used for positioning calibration first, and then according to the acidity and alkalinity of the test solution, pH 4.00 (acidic) or pH 9.18 and pHI 0.0l (alkaline) buffer solution is used for slope calibration. Correction. The specific steps are:
(1) Wash and dry the electrode, immerse it in the pH6.86 or pH7.00 standard solution, and place the instrument temperature compensation knob at the solution temperature. After the indication value is stable, adjust the positioning knob so that the instrument indication value is the pHs value of the standard solution.
(2) Take out the electrode, wash it, spin it dry, and immerse it in the second standard solution. After the indication value is stable, adjust the slope knob of the instrument so that the instrument indication value is the pHs value of the second standard solution.
(3) Take out the electrode, wash it and spin it dry, and then immerse it in the 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 in both standard solutions without adjusting the knob.
(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 still until the reading is stable.
What is the error of pH meter measurement?
In fact, pH mainly depends on the use and maintenance of personnel; if used properly and maintained in place; in fact, domestic pH meters are also very good; there will be no big problems if they are used continuously;
However, the slope of ABB is generally about 30% and can be calibrated; as for the probe in Da Na, it is useless.
In fact, as long as it can be calibrated, it will have little impact on accuracy;
