Last updated: August 16, 2021

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We are bringing you knowledge in the form of product analysis. You must like a bit of physics or chemistry to be here, don't you? After all, today's subject is PH meter.

You may have heard someone say "this is too acidic", especially a bad lemon juice. The fact is that many elements in nature have this characteristic. They are acidic, basic or neutral.

A pH-meter serves precisely to measure the acidity of a solution. And here you will learn more about them.




Summary

  • PH meters are used extensively by various branches of industry and the primary sector. For this reason, it is the most measured parameter in the world.
  • Knowing the pH of a substance is fundamental for its use in various activities. The human body, for example, is alkaline, and too much acid can bring diseases and weaknesses to our functioning.
  • Existing in several models and types of use, the pH meter can be very specific. Keep in mind what you want with them before researching, to follow a path closer to the ideal.

The best PH Meter: Our Picks

Any search on pH meters will return a considerable amount of answers. If you don't already have a good understanding of the equipment, the information can confuse rather than help. To help you out, we've rounded up some of the best.

Buying Guide

Surely the choice of a pH meter can bring up many questions. Also, their uses can be very specific, and for this reason it is important that you know them fully. We have prepared a comprehensive buying guide to help you.

imagem de um trabalhador de laboratório medindo o pH

Care is needed when measuring pH, especially of acidic solutions. (Source: Puntasit Choksawatdikorn/ 123rf)

What is a pH meter?

A pH meter (or pHmeter) is a piece of equipment used for measuring the acidity or alkalinity of an aqueous solution. PH is actually the name of the scale (and not something, per se).

It is possible to make this measurement thanks to a chemical reaction. Where the concentration of a certain element in a liquid sample is measured - it needs to be liquid, so they usually call it a solution.

The greater the amount of this element (H+) the more acidic the solution is considered to be. The most basic form of measurement uses a reagent that changes colour at different intensities as it is exposed to the analysis solution.

Thus, with the help of a colour palette (provided by the equipment), you compare the colouration and determine the pH level. Of course, there are more sophisticated equipment, with other ways of indicating the measurement.

You may not realize it, but the importance of measuring the pH is immense in several industries. They even incorporate some tests in their daily routines, to ensure certain characteristics and qualities of the product.

Pharmaceutical production, agriculture, electronics manufacturing, foodstuffs, all these industries depend on pH measurement. Thanks to this, pH is considered to be the most measured parameter in the world.

Advantages
  • Indication of the acidity or alkalinity level of the solution
  • Immediate result after measurement
  • Possibility of sample (or even lot) correction
  • Preventive measure for use or not of inputs and raw materials
Disadvantages
  • Electronic equipment needs periodic calibration
  • Continuous maintenance is required (after use)
  • Requires basic knowledge in chemistry for use

How does the pH meter scale work?

You already know that pH is, in fact, a scale to measure acidity or alkalinity. Ranging from 0 to 14, it appeared a few centuries ago where a chemist proposed that there should be a definition for acids and bases.

For this, he conducted several tests where he submitted various substances to a mixture with water, and observed the behaviour of the samples. He noticed that, according to the substance mixed, there was some kind of chemical release (of ions or anions).

And he discovered that, in certain proportions, they annulled each other. From this, the pH scale we know was developed. This measurement is made by calculating the concentration of ions (H+) present in the sample. The more of them, the more acidity.

 imagem de uma escala de pH

The scale goes from 1 to 14. The closer to 1, the more acidic. (Source: Fabien MONTEIL/ 123rf)

Without abusing chemistry, let's explain the concept of alkaline or acid as best we can. Starting with what should be new: alkaline.

  • Alkaline: A different vocabulary word, you'll really only use it in very specific situations. Probably related to pH measurement. An alkaline solution has an element left over in the reaction, of negative concentration (OH-). If you remember chemistry, you know that negative concentrations are very willing to make bonds with other compounds.
  • Acid: Exactly the opposite of alkaline, the acid solution releases a positive molecule (H+), which ends up acidifying the solution. This positive component also bonds with the negatives it encounters, generally carrying out an oxidation reaction.

This is why an acidic solution, when something is put in it, bubbles. The chemical process releases oxygen and leaves hydrogen destroying everything (relative to each acid had, as they are different compounds).

What models of pH meters exist?

Being a common practice all over the world, and of extremely intense use, there are several models of equipment to measure pH. Including some of very specific use for certain activities and products, as you will see.

Acid-Base Indicators

The simplest and cheapest method to measure pH, it is also the most generic. The model is based on using natural or manufactured substances, which react chemically to pH and change colour.

In this way, there is an oscillation in colour in a clear hue, which has great variation while in an acidic or alkaline solution. The disadvantage of these indicators is that the measurement gives approximate values.

However, it is extremely interesting to note the rapid visual change of the substance when in contact with the solution analysed. Very worthwhile!

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Pocket pH meter

These are practical options for simpler applications where cost is an important issue, with the practical advantage of portability. They also offer full functionality in a portable size.

Due to the materials used, they are recommended for occasional use as they are not very durable. However, due to the practicality of use, increasingly better equipment is designed in this model.

There are a lot of pocket pH meters available in the market, and you can make a good purchase if you pay attention to the right requirements.

Benchtop pH meters

Larger and highly complex devices, they usually provide various other information besides pH. They are suitable for use in laboratories, industries and manufacturing processes.

They are perfect for situations where most of the analysis takes place within a single environment, such as the laboratory. These models also tend to have good data management capabilities and can pass the information directly to other machines.

PH meter by use

PH meters can be so specific that there are those specifically intended for analysis of some specialties:

  • PH milk pH meter;
  • PH meter for soil;
  • PH meter for fruit;
  • Among others.

These variations occur due to the particularities of the samples, which have their own challenges. Often, they are more practical and easier to clean, or more resistant according to basic needs.

How do you calibrate a pH meter?

As a rule, every pH meter (except the reagents) needs to be calibrated. This allows for more accurate readings and prepares the electrodes to receive the ion load.

The tip is to always choose a standard solution (pH 7, the middle of the table) for calibration. If possible, also make one with the pH that you imagine to find in the sample, to make the calibration more effective.

If the information does not match, the instrument should be sent for maintenance and adjustment.

Purchase Criteria: Factors to Compare pH Meter Offers

Different in many ways, pH meters can give you a list of specifications. And some of them are not exactly helpful at the time of purchase, serving only to make up the big advantage over the competition.

If you intend to buy a pH meter, pay attention, mainly, to these criteria:

Accuracy

Depending on your goal, it is important to have a pH meter that is accurate enough. Laboratory measurements usually have a margin of error of 0.002 pH units.

To test the acidity of foodstuffs, a meter with a precision of between 0.01 and 0.02 is sufficient. And for more domestic activities (water, swimming pool), something around 0.1 is enough.

Electrodes

Electrodes are the ends of the electronic pH meter placed on the sample. They can be made of different materials and have different resistance (to moisture, more or less rigid materials).

Choose a meter that, in research on use, proves ideal for the activities you perform. And never leave it connected to the pH meter during movements. The connections are fragile and can break.

Durability

You should look for a pH meter that is robust enough for the demands you will need. Especially with regard to working environments.

A field unit should be resistant to dirt and splashing liquids, maybe even to aggressive products (very acidic solutions).

If you intend to test hot samples, such as cooked food, you need a meter that can withstand this heat (approximately 70-80 °C).

imagem de um homem usando um medidor de pH em bancada.

For testing hot samples, such as cooked food, you need a pH meter that can withstand the heat. (Source: dedmityay/ 123rf)

Connectivity

So you've purchased a pH meter and are taking measurements, but need to carry a notepad to mark them? That's something that doesn't match today's technology.

Several models have the option of connectivity to a computer or even smartphone -if the software is compatible-, so you can receive the readings on the device and record them, avoiding rework.

(Source of the highlighted image: Aleksandr Grechaniuk/ 123rf)

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