pH measurement is an important parameter in nearly every water quality application. In wastewater treatment, pH is regulated as part of discharge permitting and many treatment processes are pH dependent. In environmental sampling and monitoring, high or low pH values can be indicative of pollution.
pH is important in the food industry, as it plays a role in the taste (acid = fresh, neutral = bland, and alkaline = inedible) and the preservation of food. In biotechnology, pH must be closely monitored during the production of immunoassay solutions. These are just a few of the many applications in which pH is a valuable measurement.
What is pH Meter?
A pH meter is a scientific instrument that measures the hydrogen-ion activity in water-based solutions, indicating its acidity or alkalinity expressed as pH. The pH meter measures the difference in electrical potential between a pH electrode and a reference electrode, and so the pH meter is sometimes referred to as a “potentiometric pH meter”. The difference in electrical potential relates to the acidity or pH of the solution.The pH meter is used in many applications ranging from laboratory experimentation to quality control.
What does the pH measure?
The pH value of a substance is directly related to the ratio of the hydrogen ion [H+] and the hydroxyl ion [OH-] concentrations.
The quantitative information provided by the pH tester expresses the degree of the activity of an acid or base in terms of hydrogen ion activity.
- If the H+ concentration is greater than OH-, the material is acidic; i.e., the pH measurement is less than 7.
- If the OH- concentration is greater than H+, the material is basic, with a pH value greater than 7.
- If equal amounts of H+ and OH- ions are present, the material is neutral, with a pH of 7.
Acids and bases have free hydrogen and hydroxyl ions, respectively. The relationship between hydrogen ions and hydroxyl ions in a given solution is constant for a given set of conditions, either one can be determined by knowing the other.
Types of pH Meter
Water pH Meter
Used in water purification systems, aquariums, pools, hydroponics and other applications
Field pH Meter
Handheld field pH meters are calibrated for use on-side and in the field although can also be used in laboratories. Field pH meters are generally weather proof due to their exposure to the elements.
Soil pH Meter
Ideally used for the gardening sectors and hydroponics where it is important to monitor pH levels in soil. The Soil pH Meter generally uses a longer pH probe for testing the soil in larger plant pots.
Food pH Meter
These type of pH Meter are designed to perform tests on food without damaging the product, various models exist for different foods such as meat, dairy products, general food produce and beverages.
Industrial pH Meter
Used in industrial applications such as metal finishing, painting, dying, effluent treatment and many more.
What Are the Different Factors to Consider When Buying a pH Meter?
Monitoring of pH is important because it impacts the chemical properties of water such as solubility, acidic nature, and so on. All these factors affect its suitability for use or consumption. Also, certain organisms thrive in water at a certain pH. Here are some factors which may help when buying a pH meter:
- A typical pH meter is made of two components – a digital or moving coil pH meter, and two probes. Some pH meters may have one probe, too. If your device has two probes, perhaps both of them act as different electrodes. The probe in a single probe device is made of two different electrodes, and integrated for the purpose of simplicity. Both the pH meter and electrode must be durable as they need to withstand the contaminants, chemicals, particles, and so on in a water sample depending upon the application.
- Electrodes can be easily damaged by contaminants and chemicals, and hence a double junction electrode is always recommended. These are especially useful for applications which involve solid particles, chemicals, or sludge such as wastewater and pulp & paper.
- Both highly alkaline and highly acidic water impact its usage. For instance, highly alkaline water many not only taste bitter but also leave deposits on utensils, pipes, and so on. On the other hand, highly acidic water may react or dissolve metals and corrode the surfaces or pipes and utensils. So, the ideal pH range should be 6–8.
- Consider a 2-point calibration for acidic and basic level measurements. The former could be adjusted from 4 to 7, and the latter from 7 to 10.
- Check factors such as flexibility and portability, and the level of technology used. There are pH meters, which can function without much manual intervention.
- If you deal with dirty water, you can use a flushable junction, as they can be easily cleaned off wastewater particles, sludge, paper pulp, or any other waste.
