What is a pH standard buffer solution? What are its characteristics?
1. What is a pH standard buffer solution? What are its characteristics?
A pH buffer solution is a solution that can maintain a stable pH value. If a small amount of acid or base is added to this solution, or a chemical reaction in the solution produces a small amount of acid or base, and the solution is appropriately diluted, the pH value of the solution is basically stable and unchanged. This solution that can resist a small amount of acid or base or large or small dilution, and keep the pH value unchanged is called a buffer solution.
The pH standard buffer has the following characteristics:
(1) The pH value of Standard solution is known and reaches the specified accuracy;
(2) The pH value of Standard solution has good reproducibility and stability, larger buffer capacity, smaller dilution value and smaller temperature coefficient;
(3) The preparation method of the solution is simple;
How to prepare a pH standard buffer solution?
For general pH measurement, a complete set of pH composition reagents (capable of preparing 250mL) can be used. When preparing the solution, deionized water should be used and pre boiled for 15-30 minutes to remove dissolved carbon dioxide. Cut the plastic bag, pour the reagent into the beaker, dissolve it with appropriate amount of deionized water, rinse the packaging bag, pour it into a 250mL volumetric flask, dilute it to the scale, and shake it well.
3. How to properly store and use pH buffer solutions?
After preparing the buffer solution, it should be packed in a glass or polyethylene bottle (alkaline pH buffer solution, such as pH=9.18, pH=10.01, pH=12.46, etc., should be packed in a polyethylene bottle) with a tight lid. It should be stored in a refrigerator at low temperature (5-10 ℃) and can generally be used for about six months. If there is turbidity, mold, or precipitation in the existing mixer, it cannot be used again. When using, several 50mL polyethylene small bottles should be prepared, and the component solution from the large bottle should be poured into the small bottles. The bottles should be left at ambient temperature for 1-2 hours, and the temperature should be balanced before use. After use, it is not allowed to pour it into a large bottle to avoid contamination. The buffer solution in the bottle can be used for 2-3 days under environmental conditions>10 ℃. Generally, pH=7.00, pH=6.86, and pH=14.00 can be used for a longer time. pH=9.18 and pH=10.01 solutions absorb carbon dioxide in the air, and their pH value is relatively easy to change.
What is the purpose of a 4. pH buffer solution?
(1) Calibrate the pH meter before pH measurement.
(2) It is used to verify the accuracy of the pH meter, for example, pH=6.86 and pH=14.00. After calibrating the pH meter, 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.
(3) Check if the pH meter needs to be recalibrated during general precision measurement. After calibrating and using the pH meter, there may be drift or changes. 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.
(4) Check the performance of the pH electrode.
