This section provides an overview for digital ph meters as well as their applications and principles. Also, please take a look at the list of 10 digital ph meter manufacturers and their company rankings.
Table of Contents
A digital pH meter is a machine that measures pH.
The electrode of the device is placed directly into the sample for measurement.
This device is used in a variety of fields and for a variety of purposes because it is easy to handle and affordable.
Most digital pH meters use the glass electrode method of measurement.
Other pH measurement methods include the use of indicator such as litmus paper, the hydrogen electrode method, the quinhydrone electrode method, and the antimony electrode method, but the glass electrode method is safer, more accurate, and more reproducible than other measurement methods.
pH is one of the indicators that represent the environment of water bodies such as rivers, lakes, and marshes, and in chemical analysis, it is one of the indicators that affect sample pretreatment and analysis conditions.
In chemical analysis, it is one of the indicators that affect sample pretreatment and analysis conditions. pH also affects the progress of chemical reactions, so it is sometimes controlled at manufacturing sites.
Since pH must be measured accurately and easily in these various fields, digital pH meters are used in a variety of locations.
pH meters have different electrode dropouts depending on the application, and can be divided into porous (for general aqueous solutions) and sleeve (for viscous samples or samples containing a high percentage of non-aqueous soluble substances) types. (used for viscous samples or samples with a high content of non-aqueous soluble substances). The most appropriate pH meter should be selected based on the characteristics of the sample and container.
pH is an indicator of hydrogen ion concentration in a liquid.
The glass electrode method is described here as a typical example of a pH measurement method. This method uses two electrodes (a glass electrode and a reference electrode). When a liquid of different pH is present in the two areas separated by the glass films of the electrodes, an electromotive force corresponding to the difference is generated. The pH is calculated by measuring the potential of the glass and reference electrodes with the instrument itself.
The pH meter must be calibrated before use. pH standard solutions are generally calibrated using pH 7 as the zero point and pH 4 and pH 9 as the three-point calibration, but the pH standard solution used for calibration may be changed depending on the pH of the sample. The slope of the calibration curve is affected by temperature.
pH measurement itself is simple, but it is important to keep the temperature of the pH standard solution and the sample as close as possible, to maintain the electrode properly, and to immerse the electrode's drop firmly in the sample. Although the pH measurement itself is simple, it is advisable to have a procedure for the key points of the measurement and maintenance method.
Calibrating a PH meter means correctly adjusting the zero and span points (sensitivity) of the PH meter using a pH standard solution. Since there are operations specific to the digital PH meters used, the instructions provided with the meter should be given priority when actually calibrating the meter.
Calibration can be performed in one-point calibration using one type of pH standard solution, two-point calibration using two types, or three-point calibration using three types, but two-point calibration is often used to calibrate PH meters.
One-point calibration is a simplified calibration. For more rigorous calibration, three-point calibration is used.
The actual value of "EMF per pH" at a glass electrode is affected by contamination of the glass film and "alkaline error" and "acid error" (errors in strong alkalinity and strong acidity, respectively). Therefore, the actual value is generally lower than the theoretical value (59.16mV at 25°C). The "pH7 EMF" also deviates from the theoretical value (0 mV).
By performing pre-measurement and periodic calibration, highly accurate pH measurement can be achieved.
The general procedure for two-point calibration is described below:
These operations are span point correction.
Repeat the zero point correction to span point correction until the indicated value of pH agrees within ±0.05 of the pH against the temperature of the pH standard solution.
The types, quality, and composition of pH standard solutions are as follows:
*Including some distributors, etc.
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