Particle Imaging Techniques
Most commercial laboratories will offer you three methods of analysis to determine the digestibility of your forages and feed additives.
Near Infrared Spectroscopy (NIR) is fast and doesn’t require extensive sample preparation. NIR analytical instruments detect infrared light and interpret the type and amount of compounds present. While very accurate, only certain samples can be analysed, so NIR is the cheapest option.
In recent years we have seen an increase in the role of biologics in medicine. Biologics are medicinal products that are created by biologic processes instead of chemical synthesis; these include products such as blood, vaccines, gene therapy, allergenics or somatic cells. Because of the increased role of biologics, the need to characterise particulate matter within those biologics has increased as well. In this article, we’ll take a look at how dynamic imaging particle size analysis is being used to characterise particulates in biologics, as well as some of the factors that need to be considered when using the technology.
The early days: Light Obscuration
In the early days of particle analysis in biologics, analysts used light obscuration techniques to attempt characterisation, but this method meant they faced a few hurdles. These were as follows:
What is particle imaging used for?
Where particle size analysis is used to produce a distribution curve showing how large the majority of particles in a given solution are, particle imaging also provides the ability quantify morphological (ie. shape) characteristics of particles.
Determining particle shape parameters
When reporting particle size, we try to report just one single number for each particle; the equivalent spherical size. In image analysis reports, this is often termed the CE diameter (or Circular Equivalent diameter). However, when it comes to reporting particle shape, there are many numerical descriptions that can be used, including: length/width, aspect ratio, circularity, compactness, roughness, convexity and elongation. Most image analysis system also report parameters such as lightness/darkness, opacity and intensity. All of these parameters help differentiate one type of particle to another, which is one of the real strengths of image analysis.
Where particle sizing can only report a size distribution, image analysis can be used to quantify subtle differences in shape or optical properties. New image analysis systems also provide powerful software packages that enable classification of particles into different groups. This in turn enables users to quantify different types of materials in the one sample.
How FlowCAM works
FlowCAM is one of the more popular of the new age particle imaging systems. This system counts, sizes and images particles in a sample. The FlowCAM also provides the option of colour analysis and detection of living organisms by means of fluorescence. The measurement process is as follows:
- Particles are suspended in water
- The water is pumped through a flow cell
- Optics and a CCD camera magnify and capture an image of each particle, measuring its shape and size
- The results are displayed as a scattergram.
- The user selects distributions to display, and regions in the scattergram of particular interest can be selected and displayed in more detail.
- A library of information is housed in the system for screening future samples, if necessary.
Real life applications
In real life, particle size and shape determining technologies like those FlowCAM incorporates are used in applications like:
- Water analysis for environmental purposes, measuring things like plankton, algal blooms and levels of sedimentation
- Biotechnological settings, where quantification of enzymes or fermentation processes is needed
- Process monitoring, which covers most industrial applications – monitoring emulsions and dispersions, and in the polymer and pharmaceutical industries.
- Formulation monitoring, used for solid substances like topical cosmetics, flavour carriers, inks or pigments.