Introduction to the characteristics, accessories and preservation methods of pH standard buffer solutions

1.
What is a pH standard buffer solution? What are its characteristics?
A pH buffer solution is a solution that keeps the pH stable
.
If a small amount of acid or base is added to this solution, or the chemical reaction in the solution produces a small amount of acid or base, and the solution is properly diluted, the pH value of this solution is basically stable, which can resist a small amount of acid A solution that is either large or diluted without changing the pH value is called a buffer solution
.
The 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, and has a large Buffer capacity, smaller dilution value and smaller temperature coefficient;
(3) The preparation method of the solution is simple; 2.
How to prepare the pH standard buffer solution?
For general pH measurement, a complete set of pH group reagents (250mL 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 the beaker, dissolve it with 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
.
3.
How to properly store and use the pH buffer solution?
After the buffer solution is prepared, it should be packed in a glass bottle or polyethylene/ethylene bottle (alkaline pH buffer solution, such as pH=9.
18, pH=10.
01, pH=12.
46, etc.
, should be packed in a polyethylene/ethylene bottle) bottle Cover tightly and store it in the refrigerator at a low temperature (5-10°C).
Generally, it can be used for about six months.
If the mixer is found to be cloudy, moldy or precipitation, it cannot be used continuously
.
When using, prepare several 50mL polyethylene/ene vials, pour the group solution in the large vial into the vials, and place them at ambient temperature for 1 to 2 hours.
Wait for the temperature to equilibrate 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 a long time.
Longer, pH=9.
18 and pH=10.
01 solutions can easily change their pH values ​​due to the absorption of carbon dioxide in the air
.
4.
What is the purpose of pH buffer solution?
(1) Calibrate and calibrate the pH meter before pH measurement
.

(2) To verify the accuracy of the pH meter, for example, use 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 whether the pH meter needs to be re-calibrated during the general accuracy measurement
.
The pH meter may drift or change after being calibrated and used, so 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) Detect the performance of the pH electrode
.