Detecting small microplastics down to 1.3 μm using large area ATR-FTIR

Abstract

Large area attenuated total reflectance-Fourier transform infrared spectroscopy (LAATR-FTIR) is introduced as a novel technique for detecting small microplastics (MPs) down to 1.3 μm. Two different LAATR units, one with a zinc selenide (ZnSe) and one with a germanium (Ge) crystal, were used to detect reference MPs < 20 μm, and MPs in marine water samples, and compared with μ-FTIR in transmission mode. The LAATR units performed well in identifying small MPs down to 1.3 μm. However, they were poorly suited for large MPs as uneven particle thickness resulted in uneven contact between crystal and particle, misinterpreting large MPs as many small MPs. However, for more homogeneous matrices, the technique was promising. Further assessment indicated that there was little difference in spectra quality between transmission mode and LAATR mode. All in all, while LAATR units struggle to substitute transmission mode, it provides additional information and valuable information on small MPs.

Keywords: Ge; LAATR; Microplastics; Spectroscopy; ZnSe.