PH buffer solutions: your complete guide

PH buffer solutions are also known as pH buffer or hydrogen ion buffer. They go hand in hand with a ​​pH metre which measures the acidity and alkalinity (in other words, the pH level) of a liquid. PH buffer solutions help stabilise its pH level for industries where it is critical to achieve a consistent pH level.

PH levels are measured in a wide range of industries, including: water and wastewater treatment, chemical production, agriculture research and production, environmental monitoring, chemical and life sciences research, biochemical and pharmaceutical research, food processing, and many more.

What are pH buffer solutions?

A buffer solution is an acid or aqueous base solution that resists changes in pH levels when a small amount of an acid or alkali is added to it, keeping pH at a nearly constant value. A pH buffer solution is used to help check that your pH metre or electrode is calibrated; to ensure that it is working correctly, to help achieve a pH reading.

Acidic buffer solutions- an acidic buffer solution has a pH level lower than 7 and is made from a weakened acid and one of its salts. The pH of the solution can be altered by changing the acid-to-salt ratio or choosing a different acid and salt.
Alkaline buffer solutions- an alkaline buffer solution has a pH greater than 7 and is made from a weak base and one of its salts.

How to store and use pH buffer solutions for calibrating

The three most common pH buffer solutions are pH4, pH7 and pH10. Usually a different colour is used to distinguish between them. PH 4 is often red, pH7 yellow, and pH10 blue.

Storage 

The solution should not be used if it passed its expiry date, as your results may not be accurate. Due to the makeup of the product, pH solutions should be discarded in a responsible manner. 

Top tip

Write the value on the cap to prevent the caps from accidentally being mixed up.

How to use pH buffer solutions

When calibrating a pH device, it is best practice to calibrate pH7 before calibrating pH4 or pH10. For example, if you are operating in the acidic range, then you will calibrate with pH7 and then pH4, and if operating a Alkaline range, then you would calibrate with pH7 and then pH10.
When calibrating with different buffer solutions, be careful not to contaminate the buffers. Decant small amounts of buffer solution into separate cups and discard the contents of the cups when complete. NEVER pour decanted buffer solution back into the original bottle, as this will cause contamination.

6 steps for calibration use pH buffer solution

(assuming calibrating with pH7 and then pH4):

1. Rinse the probe with distilled water (or pH7 buffer) and dry it with a clean paper towel.
2. Decant a small amount of pH7 buffer into a separate cup.
3. Insert pH probe in cup, wait for reading to settle, and calibrate zero point (i.e. pH7)
4. Rinse the probe with distilled water (or pH4 buffer) and dry it with a clean paper towel.
5. Decant a small amount of pH4 buffer into a new separate cup.
6. Insert pH probe in cup, wait for reading to settle, and calibrate slope point (i.e. pH4)

If you do not have distilled or de-ionised water you can rinse probes using clean tap water.

We supply a wide range of pH products, ph buffer solutions, pH metres, and electrodes from leading brands such as ETI and EUTECH.