Identification of Environmental Plastic Samples from a Caribbean Beach Survey by Near-Infrared Spectroscopy with the MicroNIR and Chemometric Analysis

Abstract: MicroNIR is a portable near-infrared diffuse reflection spectroscope. Its suitability for identifying environmental plastic polymers was evaluated through a series of performance tests. The plastic samples were collected during a beach survey in the Caribbean. First a reference database was built by analysing a series of reference plastic polymers. Prediction models were constructed by using principal component analysis (PCA) and cluster analysis on 2D- and 3D-scatterplots. Measurements of samples with a surface area down to 1 mm2 were successfully identified with the prediction models. Blend spectra were created by measuring two polymers simultaneously, from which each polymer NIR-fingerprint were able to be individually extracted from the blend spectra by subtracting the NIR-fingerprint of the opposite polymer. Prediction models were used to identify the samples in the tests with household plastics and the environmental plastic samples, collected in the Caribbean. Out of the forty-eight samples collected forty (83%) were identified. Twenty-seven were identified as polyethylene (56%), eleven as polypropylene (23%), one as polystyrene (2%), and one as polyamide (2%).