What is a standard pH buffer solution? What are its properties?
A pH buffer solution is a solution that keeps the pH value stable. If a small amount of acid or alkali is added to this solution, or a chemical reaction in the solution produces a small amount of acid or alkali, and the solution is appropriately diluted, the pH value of the solution is basically stable, which can resist a small amount of acid. A solution whose pH value does not change when the base is large or dilute is called a buffer solution.
pH standard buffer has the following characteristics:
(1) The pH value of the standard solution is known and reaches the specified accuracy;
(2) The pH value of the standard solution has good reproducibility and stability, has a large buffer capacity, a small dilution value and a small temperature coefficient;
(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 group reagents (250 mL can be prepared) can be used. When preparing the solution, deionized water should be used and boiled for 15 to 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 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 solutions?
After the buffer solution is prepared, it should be placed in a glass bottle or polyethylene bottle (alkaline pH buffer solutions, such as pH=9.18, pH=10.01, pH=12.46, etc., should be placed in polyethylene bottles) with the bottle cap tightly closed. , stored in the refrigerator at low temperature (5-10℃), it can generally be used for about six months. If the mixer is found to be turbid, moldy or precipitated, it cannot be used further. When using, several 50mL polyethylene vials should be prepared, pour the combined solution in the large bottles into the vials, and leave them at ambient temperature for 1 to 2 hours, and wait for the temperature to balance before use. Do not pour it into a large bottle after use to avoid contamination. The buffer solution in the bottle can be used for 2 to 3 days under environmental conditions >10°C. Generally, the three solutions of pH=7.00, pH=6.86, and pH=14.00 can be used for as long as For a longer time, the pH value of pH=9.18 and pH=10.01 solutions is easier to change due to the absorption of carbon dioxide in the air.
