Microplastics fluorescence detection using a fiber optic probe

Fluorescence detection of microplastics in water is of increasing interest due to their common presence in drinking water, wastewater, and seawater. Nile Red dye is commonly used to label microparticles to ensure fluorescence. This work replaces complex fluorescence optics with a bifurcated coaxial fiber optic probe, showing the probe to be useful in fluorescence detection of Nile Red – dyed microparticles. A 532 nm low – power laser was directed into the probe’s excitation arm, with fluorescence emission resolved by coupling the probe’s detection arm into a spectrophotometer. Two candidate microparticles were shown to be measured using a simplified fluorescence system. Concentrations ranged from 1.95 x 106 to 5 x 108 beads per mL for Nile Red – dyed polystyrene 2 micron diameter beads. Concentrations ranged from 3.9 x 105 to 2 x 108 beads per mL for Nile Red – dyed polymethylmethacrylate 2 micron diameter beads. A battery – powered laser excitation source with the fiber optic probe and laptop – linked spectrophotometer demonstrates a field – portable small – footprint approach to measure fluorescent microparticles in water.