[Professional] The Structure and Function of PH

When we are testing and managing related drugs, the pH value is the basis for us to judge the status of the drug solution. The pH meter is an indispensable analytical tool. Anyone with relevant drug solution management experience can use and calibrate it, but do you understand its structure? Let's take a closer look here.

How PH Meters Work

The measurement of pH requires the use of an indicator electrode that is sensitive to hydrogen ions. The principle of measurement is to use a glass membrane electrode that is sensitive to hydrogen ions to detect the signal generated between the electrode and the sample solution. However, the indicator potential of the pH electrode alone is insufficient, and a second electrode is required to provide a stable reference signal or potential for the indicator electrode. To measure the pH value, two electrodes with different potentials must be used in combination. The pH electrode generates an electronic signal based on the hydrogen ion concentration, and the size of the electronic signal determines the pH of the solution.

The reference electrode does not respond to the hydrogen ion concentration, so it can provide the same and stable potential for the pH indicator electrode. The potential between the two electrodes can determine the pH value of the solution, that is, the number of hydrogen ions in the solution.

pH meter structure

The figure above is a simple structural description of the pH meter. Since the industry has different designs to meet different needs, we will not introduce and explain them here.

pH calibration sequence

The order of pH meter calibration is generally recommended to calibrate the neutral standard solution first, then the acidic standard solution, and finally the alkaline standard solution.

The main reason for this order is to use PH7 as the intermediate calibration point first, and then calibrate to acidic PH4 and alkaline PH10. This order can ensure that the instrument can obtain accurate readings in a wider pH range.

In addition, there is a detail that needs to be paid attention to in the calibration procedure. After calibrating the previous calibration solution and before proceeding to the next calibration solution, be sure to clean (preferably with pure water) the liquid remaining on the electrode, and then wipe the electrode dry with toilet paper before proceeding to the next step to ensure that the next calibration solution is not contaminated and the calibrated value is more accurate.

PH7 calibration solution -> clean electrode -> wipe dry -> PH4 calibration solution -> clean electrode -> wipe dry -> PH10 calibration solution -> clean electrode -> wipe dry -> measure

It is not recommended to calibrate the pH meter in the wrong order. If the calibration is not carried out in the correct order, calibration fluid contamination and data errors may occur, so please pay more attention.

Summarize

Calibration instruments have always played a very important role in production management. Their accuracy has a great impact on product yield. Only normal maintenance and regular external calibration can keep them in the best condition. It is also recommended to assign a dedicated person to be responsible for management, which is conducive to controlling the equipment status in the factory.