Sub-micron IR and Raman spectroscopy for chemical identification of microplastics
Microplastics have recently gained increased scientific and political exposure and are widely recognized as a pressing environmental and health issue. Research into microplastics has seen exponential publication growth with a corresponding increase in funding to investigate both human health and global environmental impacts.
This concern has driven US federal and state governmental bodies to enact new legislation and regulation, such as California Senate Bill 1422 (2018) which requires analysis of microplastics in water sources for drinking water. Additionally, the recent European Drinking Water Directive introduces new regulations for monitoring microplastics. Similar requirements are expected to be adopted internationally in coming years, driving increased demand for microplastics testing.
There are three key drivers for chemical and morphological analysis of MP particles: firstly, to understand the origins of microplastics to help take steps to reduce their release; Secondly, to assess potential hazards of microplastics to the environment and human health; and finally, to identify potential ways to remove microplastic particles from the environment.
Recent studies1-4 have suggested that when we consider the size of microplastics, the size range with the most potential to cause biological harm is the smaller size fraction (<20μm), which is therefore an important threshold to achieve.
A range of techniques are used for characterizing the many different aspects of microplastics. The most used techniques for chemical analysis of microplastics are conventional Fourier Transform Infrared (FT-IR) and Raman spectroscopy, but these techniques have several limitations in terms of spatial resolution, measurement accuracy, throughput, photodamage, fluorescence interference or other issues that prevent widespread use of these techniques for <20μm microplastic particles.
Optical Photothermal Infrared (O-PTIR) spectroscopy is an emerging but rapidly growing super-resolution technique that provides chemical analysis via infrared spectroscopy, but with a spatial resolution of ~500nm, around 10-30X better than conventional FT-IR microspectroscopy without any spectral artifacts caused by particle morphology (shape and size). O-PTIR also avoids the issues of low sensitivity, fluorescence interference, or photodamage issues that negatively impact Raman.
Microplastics scientific publications/year1
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