CPA Horoscope: The Future of Particle Analysis

For decades, particle analysis has been accomplished in horticultural science through the use of wire screenings to categorize particles according to screen sizes. Sieves, either round or square openings, determine particle size on the bases of minimum diameter and mass collected in each screen. Screens are usually stacked into a column and shaken or vibrated mechanically or manually for a determined period of time. This time usually varies according to the material. Particles that are not cubic or spherical in nature likely require more time to fall through the sieve column. Other particles may never reach the appropriate sieve screen due to their orientation on the screens. A computerized particle analyzer (CPA) (Tyler Inc.) provides particle size and shape analysis that is unencumbered by the shortcomings of sieve analysis. Tyler’s CPA analyses each particle using a camera capable of detecting particles greater than 33 microns as the particle passes through a light source. Each particle is instantly analyzed according to the size definitions chosen (Equivalent diameter, minimum feret, maximum feret, length, skeletal length, or geodetic length) and cataloged in the program’s library. Each sample measured by the CPA is stored and can be reanalyzed, filtered for specific particles, or compared to other samples. The samples can be viewed and compared in similar fashions as sieve analysis. Through histographs or line graphs, samples are distributed according to their size class. Size classes can be standard 20 or 40 size increments or can be custom selected to view any specific range of size classes. The thorough analysis from the CPA includes distributions of a sample’s particle count, length, area, volume, or length to width ratio. Distributions of a sample’s means or percent of total with each size class can be used to further characterize a sample’s true particle distribution. Better understanding of particle shapes and characteristics can improve all facets of substrate research from the engineering of these materials to their use as container growing media. The extensive implications for this new analytical instrument are not just vital to furthering substrate research, but can be plentiful in many various agricultural disciplines.