PH measurement extends far beyond the confines of a science laboratory and impacts our routine activities. Including the water we drink, the food we eat and the environment we live in, understanding pH helps us ensure our health, safety and well-being.

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We have heard so many saying this very often!

But have you ever wondered what contributes to reliable pH measurements? The three necessary components for measuring pH precisely are a meter, a sensor and a buffer. One of the components of our focus in the article is going to be the pH buffers.

What are they exactly?

Let us understand them with a quick series of questions.

Source: Mettler Toledo

The first question that may come to your mind is,

What are pH buffers?

A pH buffer is an aqueous solution designed to resist changes in pH when a small quantity of an acid or a base is added to it. It does this by acting as a weak acid or base, which reacts with added acid or base to stabilize the value of pH and maintain a consistent reading.

When an acid is added to a solution, it increases the concentration of hydrogen ions (H+), decreasing pH. Conversely, adding a base to a solution increases the concentration of hydroxide ions (OH-), increasing pH.

Hence, buffers are important for processes and reactions that require specific and stable pH ranges, such as in biological, chemical and industrial applications.

Source: Mettler Toledo

Where are they used?

They are mainly used for calibrating pH meters and sensors. pH buffers typically come in two varieties: single-use buffer sachets or bottles of buffer solution.

Source: Mettler Toledo

Certified buffers are verified and certified by DAkkS (Deutsche Akkreditierungsstelle, German Accreditation Body) accredited laboratory, with a precision of ±0.02 pH units. These buffers are traceable to a certificate of an accredited body of DKD (Deutscher Kalibrierdienst, German Calibration Service). These are measured according to ISO/IEC 17025.

NIST/DIN buffers are prepared according to DIN/ISO 19266 and follow the recommendation of the National Institute of Standards and Technology and the German Institute of Standardization, with a precision of ±0.015 pH units.

Conductivity standards are another consideration for buffer products.

Source: Mettler Toledo

Like pH buffers, conductivity standards are available in the form of single-use sachets or bottles for the solutions of 5 µS/cm, 10 µS/cm, 84 µS/cm, 500 µS/cm, 1413 µS/cm and 12.88 mS/cm. They help with the calibration and verification of conductivity sensors. High conductivity standards are the ones with high ion concentration and the low conductivity standards are the ones having low concentration of ions. However, these standards tend to be affected by dilution, contamination or the influence of carbon dioxide when in contact with air; their values change readily, especially in the case of low conductivity standards. This is why a conductivity standard cannot be kept or used for long once opened.

The 10 µS/cm standard is intended only for verification of a measurement near the pure water range as the values of lower conductivity standards are easily affected by any mishandling. On the other hand, the 84 µS/cm standard should be used for the best calibration accuracy.

Source: Mettler Toledo

We recommend that users follow a few practices for both calibration standards to attain reliable output.

Best electrochemistry practices for the usage of pH and conductivity calibration standards:

1. Mark the date on the bottle when the calibration standard is opened for the first time.

2. Always keep the calibration standards tightly sealed.

3. Use dispensed calibration standards immediately to prevent contamination.

4. Avoid pouring dispensed calibration standards back into the original bottle and mixing calibration standards from different manufacturers.

5. Ensure no contaminants enter the calibration standard's bottle.

6. Store the calibration standard at normal ambient temperatures.

7. Prevent exposing the calibration standard to extreme temperatures or direct sunlight.

8. Properly clean your electrodes before calibrating.

9. Use a separate container instead of the original solution's bottle to calibrate.

10. Refrain from using any calibration standard that has expired or is suspected of being contaminated.

11. Replace your calibration standard with a fresh bottle after it has reached the expiration date.

To conclude, proper handling of these standards involves keeping them clean, storing them in a controlled environment, using appropriate handling techniques and verifying their accuracy periodically.

We now hope this article enables you to get thorough with calibration standards and the practices to follow to get the best out of them.

Mettler Toledo offers a range of pH buffers for calibration, including technical, certified and NIST/DIN buffers. Technical buffers come with a certificate indicating a precision of ±0.02 pH units for most solutions.

Learn more about the calibration standards, buffers and solutions on Mettler Toledo’s Laboratory pH Buffer page.