A dye is a
colored substance that has an affinity to the substrate to which it is being
applied.
A new approach
is presented for analysis of microplastics in environmental samples, based on
selective fluorescent staining using Nile Red (NR), followed by density-based
extraction and filtration. The dye adsorbs onto plastic surfaces and renders
them fluorescent when irradiated with blue light. Fluorescence emission is
detected using simple photography through an orange filter. Image-analysis
allows fluorescent particles to be identified and counted. Magnified images can
be recorded and tiled to cover the whole filter area, allowing particles down
to a few micrometres to be detected. The solvatochromic nature of Nile Red also
offers the possibility of plastic categorisation based on surface polarity
characteristics of identified particles. This article details the development
of this staining method and its initial cross-validation by comparison with
infrared (IR) microscopy. Microplastics of different sizes could be detected
and counted in marine sediment samples. The fluorescence staining identified
the same particles as those found by scanning a filter area with IR-microscopy.
Cyanine dyes can
be used to quantify the amount of dsDNA within a sample. The linearity of
fluorescence, as function of DNA amount of six dyes, is obtained by measuring
the fluorescence intensity at the optimal excitation and emission maxima.
|
|