Separation, pretreatment and analysis of microplastics in freshwater, seawater and wastewater

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Σιγάλα, Ευαγγελία

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Microplastics are defined as fragments smaller than 5 mm. They have become an increasingly urgent issue today. Their effects can be aesthetic, economic, and ecological. Until now, there have been no standard methods for analyzing microplastics. Therefore. the aim of this master's thesis is the study of methods of pretreatment, separation, and analysis of microplastics in freshwater, seawater and wastewater samples. Specifically, emphasis will be placed on the method of staining microplastics with Nile Red dye for their detection by fluorometry. The work done at the lab can be divided into three parts: (1) Separation and analysis of microplastics in seawater samples, (2) use of spectrophotometry for quantifying microplastics, and (3) application of the Nile Red method for microplastics analysis. Six seawater samples were brought from various locations in the Corinthian Gulf, Greece. The sampling was done using a manta net with a 333 μm mesh size. Density separation was not needed, since due to the sea’s salt water, the microplastics naturally floated. The seawater samples were then sieved, and the microplastics were isolated using forceps and a magnifying glass. The microplastics were then weighed, counted, and categorized, depending on their color, shape, and type (film, fragment, etc). An attempt was made to use UV/Vis spectrophotometry as a mean to quantify microplastics in water samples. Standard samples were prepared using LDPE microplastics in a 1:1 methanol:acetone solution. The Nile Red staining method was used to analyze microplastics using fluorometry. Various kinds of microplastics (films, foams, etc.) made out of various plastic materials (LDPE, HDPE, PP, etc.) were stained using a Nile Red solution in order to determine the degree in which they fluoresce under blue light. The microplastics were examined under a blue light using an orange filter, in a fluorometer created in the lab. Moreover, LDPE microplastic powder was dyed and examined using the same technique. Since many films were found in our samples, special attention was given to film fluorescence.

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Microplastics, Freshwater, Seawater, Wastewater, Nile red, Fluorescence

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