Abstract
FTIR spectroscopy is usually applied for the analysis of plastics in environmental analysis as a support to the study of their effects on the aquatic living organisms. Here we present a further development of FTIR spectroscopy focused to the discrimination between biodegradable and non-biodegradable polyethylene terephthalate (PET). The FTIR spectra of conventional PET samples of different commercial and domestic uses, joint to certified biodegradable PET samples were included in a digital matrix and then submitted to principal component analysis (PCA). PCA, which explained the 89.1% of the total variance (first factor 84.1% and second factor 5.0% respectively), allowed a preliminary differentiation among non-biodegradable PET and certified biodegradable PET. This differentiation of PET was tested by means of two discriminant analysis methods, the Hotellingâs T2 test and the Mahalanobis distance, which confirmed the PCA results. A re-examination of the FTIR spectra, showed that the two absorption band ratios 898â973 cmâ1 and 1340â1370 cmâ1 are fundamental to discriminate biodegradable and non-biodegradable samples because these band ratios describe the crystalline and the amorphous characteristics of PET. The deconvolution of the CO group in the range between 1650 and 1800 cmâ1 and the application of two-dimensional correlation analysis (2DCOS) gave other support for PET discrimination because they showed other structural differences between biodegradable PET and non-biodegradable PET, related to the interactions among its the bands at 1740, 1250, 1120 and 1090 cmâ1. According to these results, it is our opinion that the discrimination between biodegradable and non-biodegradable PET evidenced by FTIR spectroscopy could be further investigated and extended to the analysis of PET present in the marine environment.
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