Does the pH meter standard buffer solution need to be prepared immediately? How to prepare?
A pH meter is a common instrument used in laboratories to measure the pH of a solution. In order to ensure the accuracy of the measurement results, the pH meter needs to be calibrated regularly with standard buffer solutions.
The standard buffer solution can be prepared in advance. The prepared solution can generally be stored for 2 to 3 months, but some solutions can only be stored for half a month to one month due to easy deterioration. If the solution is found to be turbid, moldy or precipitated, etc. continue to use. In order to obtain the most accurate calibration effect, it is generally recommended that qualified laboratories use standard buffer solutions that are prepared and used immediately.
The following Sooke Purchasing Manager will introduce to you the configuration method of the standard buffer solution commonly used in pH meters:
Three commonly used standard buffer solutions:
Potassium hydrogen phthalate (KHC8H4O4), pH 4.00;
Mixed phosphate (Na2HPO4): potassium dihydrogen phosphate and disodium hydrogen phosphate mixed salt solution, pH value 6.86;
Borax (Na2B4O7 10H2O) solution, the pH value is 9.18;
1. The preparation method of potassium hydrogen phthalate solution
Use a precision balance to weigh 10.12g of potassium hydrogen phthalate (KHC8H4O4) dried at 115±5 for 2-3 hours, add water to dissolve and dilute to 1000ml.
2. Preparation method of mixed phosphate solution
Use a precision balance to weigh 4.303g of anhydrous disodium hydrogen phosphate and 1.179g of potassium dihydrogen phosphate dried at 115±5 for 2-3 hours, add water to dissolve and dilute to 1000ml.
Preparation of phosphate standard buffer solution with pH=6.8:
Use a precision balance to weigh 3.533g of anhydrous disodium hydrogen phosphate and 3.387g of potassium dihydrogen phosphate dried at 115±5 for 2-3 hours, add water to dissolve and dilute to 1000ml.
3. Preparation method of borax solution
Use a precision balance to weigh 3.80g of borax (note: avoid weathering), add water to dissolve and dilute to 1000ml, store in a polyethylene plastic bottle, seal it well, and avoid contact with carbon dioxide in the air.
Note: The prepared pH standard solution should be diluted with a smaller beaker to reduce the pH standard solution sticking to the beaker wall.
After the pH standard buffer solution is prepared, it should be sealed and stored in a dry place to avoid deliquescence and deterioration due to high air humidity. Alkaline standard solutions should be sealed and stored in polyethylene bottles. Prevent carbon dioxide from forming carbonic acid after entering the standard solution and lower its pH value.
