What is the main function of pH buffer solution for a pH meter?
⑴ Calibration of pH meter before pH measurement
To verify the accuracy of a pH meter, for example, after calibrating the pH meter with pH 6.86 and pH 4.00, insert the pH electrode into the pH 9.18 solution and check whether the instrument display value is consistent with the pH value of the standard solution;
⑶ Check if the pH meter needs to be recalibrated during general precision measurement. After calibrating and using the pH meter, drift or changes may occur. Therefore, before testing, insert the electrode into a standard buffer solution that is close to the measured solution, and determine whether recalibration is necessary based on the magnitude of the error.
⑷ Testing the performance of pH electrodes
How to prepare pH standard buffer solution?
For general pH measurement, a complete set of pH buffering reagents (250ml can be prepared) can be used. When preparing the solution, deionized water should be used and boiled for 15-30 minutes in advance to remove dissolved carbon dioxide. Cut open the plastic bag and pour the reagent into a beaker. Dissolve it in an appropriate amount of deionized water, rinse the packaging bag, and then pour it into a 250ml volumetric flask. Dilute to the mark and shake well.
How to properly store and use pH buffer solution;
After preparing the buffer solution, it should be placed in a glass bottle or a polyethylene bottle (alkaline pH buffer solutions such as pH9.18, pH10.01, pH12.46, etc. should be placed in polyethylene bottles). The bottle cap should be tightly closed and stored at low temperature (5-10 ℃) in the refrigerator. Generally, it can be used for about two months. If turbidity, mold or precipitation are found, it cannot be continued to be used. When using, prepare several 50ml polyethylene small bottles, pour the buffer solution from the large bottles into the small bottles, and let them stand at ambient temperature for 1-2 hours until the temperature is balanced before use. After use, it should not be poured back into the large bottle to avoid contamination. The buffer solution in the small bottle can be used for 2-3 days under environmental conditions of>10 ℃. Generally, the pH 7.00, pH 6.86, and pH 4.00 solutions can be used for longer periods of time. The pH values of pH 9.18 and pH 10.01 solutions are relatively easy to change due to the absorption of CO2 from the air.
