pH Meter is a crucial scientific tool for quality control in industries, agriculture, and research. This acid-base meter helps us accurately track and control production processes, impacting the quality of products and consumer safety. Currently, pH water testing has become an important standard that various industries must adhere to.
What is a pH Meter?
A pH meter is a tool used to measure the acidity or alkalinity of solutions, also known as the pH value. It measures the concentration ratio between hydrogen ions [H+] and hydroxide ions [OH-] in various solutions, with values ranging from 0 to 14 on a logarithmic scale. The pH meter works by measuring the ratio of H+ to OH-. If the solution has a higher concentration of H+ than OH-, it is considered acidic, with a pH value below 7.
Conversely, if there is a higher concentration of OH- than H+, the solution is considered alkaline, with a pH value above 7. When both ion concentrations are equal, the solution is neutral, having a pH value exactly at 7. Measuring pH is important for quality control in industries, agriculture, and research because it accurately indicates the acidity or alkalinity of solutions.
Operation Principle of pH Meter
The operation of the pH meter relies on measuring the electrical voltage through an Electrode, which detects and sends signals in millivolts (mV) to the pH measurement device. The difference in voltage is directly proportional to the concentration of hydrogen ions in the solution. The measurement process occurs due to ion exchange between the sample solution and the internal glass electrolyte solution via a porous glass measuring electrode. However, continuous use will reduce the porosity of the glass measuring electrode, leading to a decrease in measurement accuracy.
How to Use a pH Meter
Using a pH meter correctly and accurately requires proper preparation of the pH measuring instrument, appropriate calibration, followed by measurement steps and post-use maintenance of the probe. The key steps are as follows:
- Turn on the pH meter and let it warm up by immersing the probe in water for about 30 minutes to ensure readiness and accurate measurement results.
- Calibrate the instrument by first cleaning the probe, setting the pH mode, then placing it in a buffer solution of pH 7 followed by pH 4 for acidic solutions or pH 10 for alkaline solutions.
- Stir all types of buffer solutions thoroughly with a stirrer before use to ensure uniformity and accurate calibration results.
- Pour the sample solution into a beaker in sufficient quantity to immerse the probe properly.
- Immerse the probe in the sample and press the pH measurement button. Wait approximately 2 minutes for a stable and accurate reading.
- Repeat the measurement to confirm the accuracy of the obtained value, and check that the values are consistent.
- After use, clean the probe with clean water and store it in a pH probe preservative solution to extend the life of the probe.
Standard pH Comparison Table for Drinking/Waste Disposal
Physical/Water Quality
|
Parameter |
Department of Public Health |
DHA |
SMA |
|
Acidity and Alkalinity (pH) |
6.5-8.5 pH |
6.5-8.5 pH |
6.5-8.5 pH |
|
Turbidity (NTU) |
Not more than 5 NTU |
Not more than 5 Silica Scale |
Not more than 5 NTU |
|
Water Color (Color) |
Not more than 15 Platinum-Cobalt |
Not more than 20 Hazen Units |
Not more than 5 Platinum-Cobalt |
|
Odor |
Not specified |
Must not have odor (chlorine excepted) |
Not specified |
General Chemical Water Quality
|
Parameter |
Department of Public Health |
DHA |
Anchor. |
|
Total Dissolved Solids (TDS) |
Not more than 1,000 mg/L |
Not more than 500 mg/L |
Not more than 500 mg/L |
|
Hardness |
Not more than 500 mg/L |
Not more than 100 mg/L |
Not more than 100 mg/L |
|
Sulfate |
Not more than 250 mg/L |
Not more than 250 mg/L |
Not more than 200 mg/L |
|
Chloride |
Not more than 250 mg/L |
Not more than 250 mg/L |
Not more than 250 mg/L |
|
Nitrate |
Not more than 50 mg/L |
Not more than 4 mg/L |
Not more than 4 mg/L |
Fluoride |
Not more than 0.7 mg/L |
Not more than 0.7 mg/L |
Not more than 0.7 mg/L |
|
Linear Alkylbenzene Sulfonate |
Not specified |
Not more than 0.2 mg/L |
Not more than 0.2 mg/L |
|
Phenolic Substances |
Not specified |
Not more than 0.001 mg/L |
Not more than 0.001 mg/L |
