From millimeters to sub-nanometers, accurately measuring particle size is essential in determining the usefulness and performance characteristics of a material.
There are advantages and disadvantages to every particle sizing technique. There is also a wide variety of instruments to choose from. In the Guide to Choosing a Particle Sizer
by Bruce B. Weiner, Ph.D., common pitfalls in selecting a particle sizer include “trying to satisfy several different requirements with one instrument” and “misunderstanding the best use for different techniques.”
Since there are many variables to consider, what should you know before purchasing a particle sizer? Patrick Lennox of Micromeritics Instrument Corp. offers “The particle sizing instrument selected for use in a specific application must be suitable for use with the material to be measured and for the environment in which the instrument is to be operated. It also must provide data to meet the specific needs of the application. This may be fast, repeatable analyses, or it may be high-resolution and very accurate results or high reproducibility of measurements from facility to facility. The determination of particle size distribution seldom is the ultimate objective; determining how particle size affects something else is usually the reason for the measurement. In this regard, the physical process actually being studied is of primary interest, but particle size is the best way or the conventional way to quantify an influencing parameter. For example, sediment from an extinct river delta may be analyzed for size. But, what actually is of interest is the deposition mechanism. In this case, size is a way of expressing sedimentation velocity and the sedimentation size (Stokes size) may be of more value than the size determined by light scattering (Mie size).”
Different techniques are likely to produce different size results for the same particle, and all of them are likely to be correct. Lennox suggests that, “The best instrument for the application (the best size definition) is the one that most closely relates particle size to the application of the particles.”
Once you have a particle sizer, how can you get the most out of it? Lenox answers, “Since different techniques are likely to produce different results, the operator needs to understand how the instrument responds to various types of materials and to different shapes. It is also important to be able to recognize erroneous data in the raw data set and understand how the error will propagate through the reduced data.”
CILAS PARTICLE SIZE
The Cilas line of high-resolution laser particle size analyzers are designed with multiple lasers for the highest accuracy and precision. A fully automated dispersion unit ensures reproducible results for even the most challenging samples. A new high-resolution imaging system allows for the analysis of particle shape down to 1 micron. The patented dispersion technology integrates wet and dry dispersion modes, eliminating the need for hardware changes. Cilas provides a wide range of analyzers, from entry level to research grade models. The analyzers are fully ISO 13320 and USP 429 compliant.
With a measurement range from 10 nm to 2000 µm, the FRITSCH Laser Particle Sizer ANALYSETTE 22 NanoTec offers entry into the nano range. This is achieved through the use of a second laser beam that is directed at the sample from behind, allowing for detection of the back-scattering light. The patented capability to move the measurement cell within the beam path of the optical system results in a high number of effective detection channels, which lead to a correspondingly high number of particle size classes and high resolution. The ANALYSETTE 22 also analyzes particle size distribution and the particle shape in a single measurement.
MICROMERITICS Micromeritics Elzone® II 5390 particle size analyzer
determines the size, number, concentration, and mass of a wide variety of organic and inorganic materials. The electrical sensing zone method is capable of accurately sizing samples of varying optical properties, densities, colors, and shapes. The Elzone determines particle size in a range suitable for a wide variety of industrial, biological, and geological specimens down to 0.4 micrometer. Extensive statistical analysis features are included. In addition, optional Confirm™ 21 CFR Part 11 software assists with compliance to FDA regulations.
The Morphologi G3 high sensitivity particle characterization system
from Malvern Instruments investigates batch-to-batch variation in a powder feed or product. From the database of size and shape measurements generated by the Morphologi G3, the data comparison tool rapidly identifies the parameters responsible for batch-to-batch variation.
The Morphologi G3 measures particle size and shape parameters for tens of thousands of particles in a sample in just minutes, generating significant quantities of information. The new comparison tool allows selected sets of data to be compared on the basis of any recorded variable.
Like this article? Click here to subscribe to free newsletters from Lab Manager