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A buffer is an aqueous solution that can resist changes in pH levels on dilution or on the addition of a small amount of acid or alkali. It is made up of a weak base and its conjugate acid, or a weak acid and its conjugate base.
The pH of an acidic buffer is less than 7. It generally consists of a weak acid and one of its salts (conjugate base). A commonly used example would be a mixture of ethanoic acid and sodium ethanoate in solution. This has a pH of 4.76 when you combine equal molar concentrations of ethanoic acid and sodium ethanoate.
An alkaline buffer generally consists of a weak base and one of its salts (conjugate acid). Its pH is greater than 7. An example of an alkaline buffer would be a mixture of equal molar concentrations of ammonia and ammonium chloride. This results in a solution with a pH of 9.25.
When small amounts of a strong base (OH–) are added to a buffer, the buffer will resist changes in its pH by supplying an equal amount of its weak acid to donate a proton to the base. Similarly, when small amounts of strong acid (H+) are added to a buffer, the buffer will resist changes in its pH by supplying an equal amount of its weak base to accept a proton from the strong acid. The conjugate acid will neutralize any added base (OH- ions) and the conjugate base neutralizes any added acid (H+ ions).
Buffer capacity is the measure of a buffer’s ability to resist pH change. This ability depends on the concentration of the buffer components. A higher buffer concentration has a greater buffer capacity. This means that a greater amount of hydrogen ions, or a stronger acid, would have to be added to disrupt the equilibrium and change the pH of the buffer.
It is important to calibrate your pH electrode regularly to ensure accurate results. Failure to do so will result in inaccurate measurements of your pH. A single point calibration can be used when you are looking to measure a consistent pH value with little variation. This method involves using a single buffer solution as a reference for calibration. The most common calibration, however, is the two point calibration and is best suited when you have a range of pH samples. The buffer solutions should bracket your expected pH sample.
Sentek has been providing innovative electrochemical solutions since 1991. We have a wide range of accessories and consumables, all tested for use with our pH, conductivity, ISE and reference electrodes.
Each buffer solution and buffer capsule provided by Sentek is traceable to NIST standards, so you know you are getting the best quality. Our buffer capsules have a longer shelf life as opposed to pre-made solutions, so offer great value. We also have plenty of accessories to clean and store your pH, conductivity, ISE, and reference electrodes safely.
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