Profile
Settings
Refer your friends
Sign out
Buffer preparation is a common process in chemistry and biochemistry laboratories. A buffer solution is a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid.
Buffer solutions are used to help maintain a stable pH value of another solution that is mixed with the buffer. The buffer resists changes in the pH value of the whole solution when a small amount of a different acid or alkali is introduced into the solution either through addition or via any chemical reaction within the solution.
Buffer solutions are therefore very useful in a wide variety of applications in which a relatively stable pH is required. A buffer may also be called a pH buffer, hydrogen ion buffer, or buffer solution.
For example, blood contains natural buffers to maintain a stable pH of between 7.35 and 7.45 so that our enzymes work correctly.
As enzyme activity varies with pH, maintaining a constant pH is essential in biochemical assays to ensure the correct level of activity is observed. In commercial applications, buffers can be found in shampoos to prevent skin irritation, in baby lotions to inhibit the growth of bacteria, and in contact lens solutions to ensure the pH level of the fluid remains compatible with that of the eye.
Preparing buffers consists of several steps: Weighing-in the components, dissolving the components, adjusting the pH and replenishing to the final volume.
As the ratio of the acid to base in a buffer is directly related to the final pH, it is vital to weigh the components with a high degree of accuracy. So, it is important that the equipment used (balance, pipettes and pH meter) are properly calibrated and have sufficient accuracy.
Buffer Solution Preparation
To optimise component separation and lengthen column life, the pH of the mobile phase (eluent) is changed.
As far as feasible, this pH correction should include employing buffer solutions rather than just dropping in an acid or alkali. If buffer solutions are not employed, good separation repeatability (stability) may not be attained.
A buffer solution is made by mixing weak acids with their salts (sodium salts, for example) or weak alkalis with their salts.
1) pouring an acid (or alkali) into an aqueous solution of a salt while measuring the pH with a pH metre and
2) creating an aqueous solution of acid with the same concentration as the salt and mixing while measuring the pH with a pH metre are two common preparation methods.
If the buffer solution is employed as an HPLC mobile phase, however, even minor pH variations can cause separation repeatability issues. As a result, every pH metre that is used should be thoroughly inspected and calibrated. This page describes a procedure that does not require the use of a pH metre. As stated in the table below, the procedure entails weighing theoretically computed fixed quantities of salt and acid (or alkali). Consider the following key points.
Buffer Solutions Are Denoted By The Letters BUFFER
For example, a buffer solution labelled “100 mM phosphoric acid (sodium) buffer solution pH = 2.1” has phosphoric acid as the acid, sodium as the counterion, 100 mM total phosphoric acid group concentration, and a pH of 2.1.
Close To the Acid (Or Alkali) pKa, The Buffer Action Is At Its Peak
The pH of an acetic acid (sodium) buffer solution made from 1:1 acetic acid and sodium acetate, for example, is roughly 4.7 (close to the acetic acid pKa), and here is where the highest buffer action may be attained.
As Concentration Rises, So Does Buffer Capacity
An acetic acid (sodium) buffer solution’s buffer capacity is greater at 100 mM than at 10 mM, for example. At larger quantities, however, precipitation is more likely.
Salt Solubility And Precipitation Should Be Avoided
The solubility of salt varies depending on the type of salt used, such as potassium or sodium salt. When an organic solvent is added, salts precipitate more quickly.
Conclusion
Buffer preparation is a common process in chemistry and biochemistry laboratories. A buffer solution is a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid.
Buffer solutions are used to help maintain a stable pH value of another solution that is mixed with the buffer. The buffer resists changes in the pH value of the whole solution when a small amount of a different acid or alkali is introduced into the solution either through addition or via any chemical reaction within the solution.
Buffer solutions are therefore very useful in a wide variety of applications in which a relatively stable pH is required. A buffer may also be called a pH buffer, hydrogen ion buffer, or buffer solution.
