Microplastics are defined as plastics ranging from 1 micrometer to 5 millimeter in size. They can be diagnosed below an optical microscope baded on their diagnostic characteristics, but this method is very challenging due to limitations in probing tiny particles smaller than 50 micrometer. In most cases, to investigate and detect microplastics regarding their diagnostic properties, it is needed to handle and prob them using a needle below the microscope. Hence, what would be the best approach to assess all size range of microplastics? Maybe it is better to only report the number of larger microplastics. What is your idea?
It is possible to use a particle sizer. This instrument typically deals with the smaller size ranges, from several nanometers up to 20um, depending on the specs of the instrument itself.
I think it is best to give a size distribution for the particles in your sample rather than selecting only the largest particles. Examining microplastic particles under a microscope is the route that most people are taking. To do this, I think that the characteristics of you particles will steer the method(s) that you choose:
If you have a large sample of microplastic particles (>1mg), then imaging and characterizing all of them can be labor intensive. You can scoop out a subsample of known weight and spread it out in a dish or on a slide to count, image, or otherwise characterize them using a microscope. We have also used a method where we disperse a known weight of particles in a known volume of a type of solution in which they are neutrally buoyant (e.g., polypropylene in 70% ethanol) so they are evenly dispersed. Then pull out a subsample of known volume (e.g., 20ul) and spread it on a slide so that they particles don't clump up or overlap. You can then do the analysis. See similar procedures in methods and supplemental of Article Chronic microfiber exposure in adult Japanese medaka (Oryzias latipes)
If you have a heterogenous sample where you cannot see both large and small particles at a low magnification (
Dear @Melissa,
Many thanks for your comprehensive, valuable explanations. It will definitely help me a lot. I should take a look at the methodologies in articles you sent. I've been looking for finding the most efficient method for detecting and counting very tiny microplastics. I'm so pleased that you are interested in following this issue.
Best regards!
Mohammad.
Selected samples were also documented in FESEM.Analyzes were performed in our laboratory, but I do not remember a completely detailed analytical procedure. The sample was filtered (water pump) through a membrane nitrocellulose filter and subsequently stained with Bengal red solution. The microparticles on filters were then examined in an optical microscope (obj. 20 and 40x) and documented. Selected samples were also documented in FESEM.
Preprint Microplastics, an Emerging Concern: A Review of Analytical T...
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