Environmental researchers wish to measure the size, shape, and chemical identity of every plastic particle in a sample. Because smaller particles are thought to be the most biologically relevant, this analysis must extend to particles on the micron scale. Unfortunately, traditional techniques such as visual inspection are slow, manually intensive, and prone to operator bias. As a result, investigators have recently turned to chemically specific vibrational spectroscopy, which can be used in a microscope format for particle analysis at greater speeds. Spectral microscopes acquire a spectrum guided by a visible-light image to determine a particle’s chemical identity along with its size and shape. Still, these instruments have drawbacks. Raman microscopes struggle to identify fluorescent particles, while array-based FTIR (Fourier transform infrared) microscopes generate a large number of spectra which are redundant or taken in the empty space between particles. Finally, the massive datasets generated by these microscopes introduce processing and storage challenges. The Agilent 8700 LDIR Chemical Imaging System is a breakthrough solution for rapid, automated, non-destructive analysis of microplastic particles. The quantum cascade laser (QCL) light source allows tight focusing of the bright infrared light at the precise center of each particle, identifying micron-scale particles in a matter of seconds. The unparalleled degree of system automation means that it can leverage both high-magnification visible-light and infrared images to locate all particles present in a sample and interrogate each one using either infrared transflection or attenuated total reflection spectroscopy. Finally, built-in microplastic libraries are automatically applied to identify every particle. The speed of each spectrum, coupled with the degree of automation and efficiency of the analysis, leads to significantly shorter time-to-answers. Here, we present results of a complete microplastics characterization and quantitation workflow using the 8700 LDIR on real-world samples. All spectra and images are synthesized into lists of particles present, their typical shapes and sizes, and the overall abundance of each plastic. These results demonstrate the advantages in measurable particle size, specificity, usability, and throughput that LDIR brings to the analysis of environmental microplastics.

Rapid, automated analysis of microplastics using laser direct infrared imaging and spectroscopy

2019 Spring National Meeting

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