Why is it necessary to calibrate a pH meter?

  1. What is a pH meter?
  2. What is pH meter calibration?
  3. What types of pH meter calibration are there?
  4. Why perform pH meter calibration?
    1. To maintain accuracy:
    2. To avoid drift:
    3. To account for the differences:
    4. Modification of functionalities:

Regular pH meter calibration is best to stay in pH measurement because calibration keeps readings reliable and accurate. You can calibrate the pH meter using standard pH calibration solutions (pH 07.00, pH 04.00 and pH 09.20) and they are readily available.

What is a pH meter?

A pH meter is a scientific laboratory device that determines the acidity or alkalinity of water-based sample solutions by measuring the activity of hydrogen ions.

A membrane in a pH meter lets H+ ions pass through, allowing current to flow and providing voltage. The strain is measured by meter and you tell it which standard buffer it should be in. To determine the pH of the sample solution, the pH meter compares the voltage of the unknown solution with that of the buffers.

Litmus paper (blue or red), pH paper, and universal indicator are some of the pH determination methods available. However, a pH meter provides the most accurate results over the entire pH range.

What is pH meter calibration?

The process of calibrating the pH meter by measuring liquids with a known pH value is called pH calibration. This is important because the properties of your electrode may change over time and this needs to be compensated for. A calibration completes this operation by matching the current characteristics of the pH probe to the pH meter.

What types of pH meter calibration are there?

There are one-point, two-point, and three-point or multi-point calibration options for pH meters. When it is necessary to test a constant pH value with little variation, a single point calibration can be used. In one-point calibration, only a buffer solution is used as a calibration reference.

In 3-point calibrations, three buffer solutions such as pH 04.00, 07.00 and 09.20 are used for the calibration procedure covering the entire pH range (acid, neutral and basic). To maintain the accuracy of your pH meter, at least three standards are needed to create a calibration curve.

Why perform pH meter calibration?

The calibration of the pH meter is important and is done to maintain the accuracy of the results, to avoid drifts, to take into account the differences and to see the changes in its characteristics.

To maintain accuracy:

It is necessary to calibrate the pH meter to maintain the accuracy of the results. Calibrating the meter without results from standardized pH buffer solutions will be unnecessary and incorrect.

To avoid drift:

Most pH meters, and electrodes in general, are notorious for deviating from their calibrated parameters. Drift from the calibrated setting cannot be avoided; However, it is important to calibrate your pH meter frequently to ensure that you continue to get accurate results.

To account for the differences:

During calibration, the use of standardized buffers also eliminates differences between samples. Differences in ionic strength and other membrane-related problems can be avoided with proper standards.

Modification of functionalities:

The characteristics of pH electrodes can change over time due to aging and coating, and even the most stable electrodes cannot be manufactured with the same characteristics. Calibration helps to match the current characteristics of the pH meter to the pH sensor used, it compensates for any differences in behavior of the pH electrode in theory and in reality.

Electrodes are based on displacement and tilt, but with age all electrodes will change. In fact, at all times the electrodes will not behave according to the Nernst equation.

This is the reason, where calibration comes from. When a known buffer is used, the appropriate calibration will be prepared for the old electrode by determining the actual offset and tilt to match and update the pH meter algorithm.

If the calibration results are not suitable or are not reproducible according to the standard solutions, it is a sign that the electrode of the pH meter is dirty, too old or damaged and that you want to change it.

Frequently asked Questions:

What is the purpose of calibrating the pH meter?

The purpose of calibration is to ensure that the instrument's readings are consistent and accurate.

What solution is used to store the glass electrodes?

It is recommended to store pH electrodes in KCL 04M solution, if KCL 4M is not available, use pH 04.00 buffer solution to store them.

When should a pH meter be calibrated?

In the case of high precision measurements, the pH meter must be calibrated before each test, and for normal precision measurements, it can be calibrated in a week or more.


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