Particle size analysis can seem a complex and intricate area. The thought of attempting to measure and draw conclusions about microscopically small particles can seem incredibly confusing and the techniques used to measure particles can perhaps seem daunting. Particle size analysers are of great use in achieving such measurements and techniques such as laser diffraction assist us to understand more about the properties of materials.

However, in order to understand some of the higher level concepts related to this area, it is necessary to have a sound grasp of the concepts that inform results.

Mean, median and mode

These three terms are too often confused and thought to mean the same thing. Far from being one and the same, these terms require definition:

Mean – Mean relates to the arithmetic average of the data.

Median – When concerned with particles, median is the value of the particle size that precisely divides the population into two halves. This means that there is 50% of the population above and 50% of the population below the value.

Mode – Mode defines the most common value in a frequency distribution. This also corresponds to the highest point of the frequency curve.

Common methods of particle size measurement

Because different dimensions of the particle are measured when different techniques are used, different results are obtained. Of the different methods of measurement, each has its own advantages and disadvantages.

Sieves

While this is an old technique, it has the advantage of being cheap and particularly useful for the measurement of large particles. In industries such as mining, this can be particularly useful.

The main disadvantages associated with this technique include: it is not possible to measure sprays or emulsions and measurement of dry powders is also difficult when particles become small. Wet sieving can help to overcome this problem, but it is then very difficult to reproduce results. Materials such as clay, which are cohesive and agglomerated, are also difficult to measure.

As particles tend to orientate themselves through the sieve, operating methods and measurement times need to be standardised if accurate and meaningful results are to be obtained.

Sedimentation

This has been a common method used (historically) in clay and ceramics industries.

There are two main problems with this process: the density of the material is needed and so it is not useful for determining particle size of emulsions where the material does not settle or for dense materials where the material settles quickly. Samples containing components of mixed density can not be accurately resolved. Measurement of small particles is very slow and therefore the process of repeating testing can be tedious.

Electrozone testing

This technique is very good for measuring red blood cells, but for real, industrial materials there are quite a few problems. It is very difficult to measure emulsions and dry powders and it is impossible to measure sprays. It is necessary to measure in an electrolyte and the required calibration standards are expensive.

Laser Diffraction

This is an often favoured technique that is considered to be one of the most accurate and reliable. It has a number of important advantages:

• It is very flexible and can measure all types of particles (powders, emulsions, suspensions and sprays)
• It is very rapid (answers can be produced in less than sixty seconds)
• It offers an absolute method of particle analysis that is grounded in scientific principles and makes it possible for measurements to be taken without the need to calibrate any instrument against the standard
• The technique provides a very wide and dynamic range
• It is possible to measure an entire sample
• The technique is highly repeatable.

Combine technique with instrument

The technique used to measure particle size will depend on the material being analysed, and the instrument used should be one of the highest quality. ATA Scientific is a trusted brand selling a range of scientific instruments suited to measuring particle size. Contact us today to find the right instrument for you.

When you’re investing money in scientific equipment, such as a laser diffraction particle size analyser, it’s important to investigate your options before making a final decision. These days getting value for money is just one of the important considerations you need to make.

Naturally, the complexity of scientific equipment means that it is important not only to choose the equipment itself but also the supplier as well. After all, equipment of such high sensitivity and precision will undoubtedly require the backup of a supplier capable of continued support long after the deal is sealed.

That’s why it’s important to look at the supplier with a critical eye to make sure you are going to get value for money and also professional backup when you need it. Whilst it is true that all manufacturers have a legal responsibility when it comes to supplying any piece of equipment, it will be of little comfort to an aggrieved purchaser if the supplier only wants to perform its legal requirements.

What you need is reassurance that your supplying company will stand beside you over the long term and be capable of providing any assistance necessary to keep your equipment in prime operating condition.

Criteria for choosing a supplier

With this in mind, let’s take a look at some of the criteria against which you should assess your scientific equipment supplier.

Testing

In the first place, you should be looking for the equipment to receive pre-sales testing to ensure that it is properly certified and that the manufacturers requirements are being met. This is often the first sign of a quality supplier and it should be offered upfront at no cost.

Training

Don’t underestimate the training requirements. New pieces of equipment often require some time to get used to, that’s why it’s important to anticipate any training needs that will be necessary to bring your staff up to speed with the new purchase. It is at this point that you need to reassure yourself that the supplier can also provide the on-site training you will need.

Maintenance

All equipment needs to be maintained in accordance with the manufacturer’s specifications and with any regulatory requirements that are in place. Make sure your scientific equipment supplier is in a position to offer this.

Repairs

There will be times when equipment needs to be repaired so it is imperative to ensure that your supplier is in a position to do this. Every quality supplier should have a well equipped workshop and also be flexible enough to provide you with an on-site repair service.

Stock

If your equipment requires the regular supply of consumables, make sure your supplier is able to provide these for you ex-stock. There is nothing more frustrating than waiting for supplies to be imported not to mention the costly downtime you will experience.

Choose ATA Scientific as your supplier

These simple steps make it easier to purchase something like a particle size analyser by choosing a competent scientific equipment supplier which gives you the peace of mind that you need when making such a significant investment. ATA Scientific is a trusted supplier of scientific instruments, so contact us today to find out how we can help you find the instrument you need.