Basic knowledge in the use of pH meter
1. What is a pH standard buffer solution? What are its characteristics?
A pH buffer solution is a solution that keeps the pH value stable. If a small amount of acid or base is added to this solution, or a small amount of acid or base is produced by the chemical reaction in the solution, and the solution is properly diluted, the pH value of the solution is basically stable. A solution that is diluted with a large or small base without changing the pH value is called a buffer solution.
The pH standard buffer has the following characteristics:
1.1 The pH value of the standard solution is known to the specified accuracy.
1.2 The pH value of the standard solution has good reproducibility and stability, and has a large buffer capacity, small dilution value and small temperature coefficient.
1.3 The preparation method of the solution is simple.
2. How to prepare pH standard buffer solution?
For general pH measurement, a complete set of pH buffer 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 the plastic bag and pour the reagent into a beaker, dissolve it with an appropriate amount of deionized water, rinse the packaging bag, then pour it into a 250mL volumetric flask, dilute to the mark, and shake well.
3. How to properly store and use pH buffer solution?
After the buffer solution is prepared, it should be packed in a glass bottle or a polyethylene bottle (alkaline pH buffer solutions such as pH 9.18, pH 10.01, pH 12.46, etc. should be packed in a polyethylene bottle). (5-10°C) storage, generally can be used for about six months, if found to be turbid, moldy or precipitated, can not continue to use. When using, several 50mL polyethylene vials should be prepared, pour the group flushing solution in the large bottle into the vials, and place it at ambient temperature for 1-2 hours, and then use it after the temperature is balanced. Do not pour it into a large bottle after use to avoid contamination. The buffer solution in the bottle can be used for 2-3 days under the environmental conditions of >10°C. Generally, the three solutions of pH 7.00, pH 6.86, and pH 14.00 can be used for a longer time. The pH values of pH 9.18 and pH 10.01 solutions are relatively easy to change due to the absorption of carbon dioxide in the air.
4. What are pH buffer solutions used for?
4.1 Calibrate and calibrate the pH meter before pH measurement.
4.2 To verify the accuracy of the pH meter, for example, after calibrating the pH meter with pH 6.86 and pH 14.00, insert the pH electrode into the pH 9.18 solution, and check whether the displayed value of the instrument is consistent with the pH value of the standard solution.
4.3 Check whether the pH meter needs to be re-calibrated during the general accuracy measurement. After the pH meter is calibrated and used, it may drift or change. Therefore, before the test, insert the electrode into the standard buffer solution that is close to the solution to be tested, and determine whether it needs to be re-calibrated according to the size of the error.
4.4 Check the performance of the pH electrode.
