Regular calibration of pH meter is best to maintain in pH measurement since calibration maintains the readings reliable and accurate. You can calibrate the pH meter using the standard pH calibration solutions (pH 07.00, pH 04.00, and pH 09.20) and they are easily available.
What is a pH meter?
A pH meter is a scientific laboratory apparatus that determines the acidity or alkalinity of water-based sample solutions by measuring hydrogen-ion activity.
A membrane in a pH meter allows H+ ions to pass through, allowing current to flow and providing voltage. The voltage is measured by the meter and you tell it what standard buffer it should be in. To determine the pH of the sample solution, the pH meter compares the voltage of the unknown solution to that of the buffers.
Litmus paper (blue or red), pH paper, and universal indicator are some of the methods of pH determination that are available. However, a pH meter provides the most accurate results across the entire pH range.
What is calibration of pH meter?
The process of calibrating the pH meter by measuring liquids with a known pH value is known as pH calibration. This is important because the properties of your electrode can vary over time, and this needs to be compensated for. A calibration completes this by matching the current characteristics of the pH sensor to the pH meter.
What types of pH meter calibration are there?
There are single-point, two-point, and three-point or multi-point calibration options for pH meters. When need to test a consistent pH value with low variation, single-point calibration can be used. In, single-point calibration, only one 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 that covers the entire pH range (acidic, neutral, and basic). To maintain the accuracy of your pH meter at least three standards are required to create a calibration curve.
Why you need to perform pH meter calibration?
The calibration of the pH meter is important and it is performed to maintain the accuracy of results, to avoid drift, to account for differences, and to see the changes in their characteristics.
To maintain accuracy:
It is necessary to calibrate the pH meter to maintain the accuracy of the results. Calibrating the meter without standardized pH buffer solutions results will be useless and incorrect.
To avoid drift:
Most pH meters, as well as electrodes in general, are known to drift from their calibrated settings. Drift from calibrated settings cannot be avoided; however, it is significant to calibrate the pH meter frequently to make sure that you keep getting accurate results.
To account for differences:
When calibrating, using standardized buffers also helps eliminate differences between samples. Ionic strength differences and other membrane-related issues can be avoided with proper standards.
Changing characteristics:
The characteristics of pH electrodes can change over time due to aging and coating, and even the most stable electrodes cannot be made with the same characteristics. Calibration helps match the current characteristics of the pH meter to the pH sensor in use, compensates for any difference in the behavior of the pH electrode in theory and reality.
The electrodes are based upon the offset and slope, but, at the age, all the electrodes will change. Actually, at all times the electrodes will not behave as per the Nernst equation.
This is the reason, where the calibration arrives. When using a known buffer, proper calibration will be ready for the old electrode by determining the actual offset and slope to match and update the algorithm of the pH meter.
If the calibration results are not proper or not reproducible as per the standard solutions, it is a signal that the electrode of the pH meter is dirty, too old, or damaged and wants to be changed.
FAQ (Frequently Asked Questions):
What is the purpose of calibration of pH meter?
The purpose of calibration is to ensure that instrument readings are consistent and accurate.
Which solution is used to store glass electrodes?
The pH electrodes are recommended to be stored in a 04 M KCL solution, if 4 M KCL isn't available, use a pH 04.00 buffer solution to store them.
When should a pH meter be calibrated?
In the case of high-accuracy measures, the pH meter must be calibrated before each test, and for normal-accuracy measurements, it can be calibrated in a week or more.
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