Identification and Quantification of Microplastics in the Marine Environment Using the Laser Direct Infrared (LDIR) Technique

Abstract

Here, we evaluate for the first time the performances of the newly developed laser direct infrared (LDIR) technique and propose an optimization of the initial protocol for marine microplastics (MPs) analysis. Our results show that an 8 μm porosity polycarbonate filter placed on a Kevley slide enables preconcentration and efficient quantification of MPs, as well as polymer and size determination of reference plastic pellets of polypropylene (PP), polyethylene (PE), polystyrene (PS), polyvinyl chloride (PVC), and polyethylene terephthalate (PET), with recoveries ranging from 80–100% and negligible blank values for particle sizes ranging from 200 to 500 μm. A spiked experiment using seawater, sediment, mussels, and fish stomach samples showed that the method responded linearly with significant slopes (R 2 ranging from 0.93–1.0; p < 0.001, p < 0.01). Overall, 11 polymer types were identified with limited handling and an analysis time of ca. 3 h for most samples and 6 h for complex samples. Application of this technique to Mediterranean marine samples (seawater, sediment, fish stomachs and mussels) indicated MP concentrations and size distribution consistent with the literature. A high predominance of PVC (sediment, fish stomachs) and PE and PP (seawater, mussels) was observed in the analyzed samples.

Analysing micro- and nanoplastics with cutting-edge infrared spectroscopy techniques: a critical review

“…As an alternative, the direct placement of an IR transparent filter containing MPs onto an IR reflective slide has been proposed. 83…”

“…As an alternative, the direct placement of an IR transparent lter containing MPs onto an IR reective slide has been proposed. 83 Rather than measuring residual IR radiation, O-PTIR microscopes measure the sample's intrinsic IR absorption by monitoring changes in the intensity of the visible laser probe. In principle, in the reection mode, as long as the visible light (the probe) can escape from the sample surface and reach the detector, O-PTIR spectra can be obtained.…”

Mass Spectrometry Insight for Assessing the Destiny of Plastics in Seawater

“…Another research avenue to be pursued before long is research toward unveiling the structural changes in plastics during degradation as well as the structure of disintegrated fragments. With this goal in mind, we will rely on using a selection of complementary spectroscopic techniques such as Fourier transform IR [ 15 ], laser direct IR [ 38 ] and NMR [ 8 ].…”

Laser microdissection pressure catapulting (LMPC): a new technique to handle single microplastic particles for number-based validation strategies

“…Furthermore, LDIR was applied for size determination and counting of the particles after pressure catapulting. The operation principles of LDIR are described in previous publications [13,17,20,21]. The slides were scanned at the wavenumber 1799 cm −1 .…”