분광분석법을 이용한 미세플라스틱 분석법 비교: FTIR을 이용한 수동, 반자동, 자동분석 및 Raman을 이용한 수동분석

Abstract

The vibrational spectroscopy such as Fourier transform infrared (FTIR) and Raman microscope is popular microplastic analytical method for their quality and quantity. The spectroscopy can confirm the polymer composition, however, still it is unavoidable to human bias by manually selecting plastic-like particles for FTIR analysis using microscope. We tried to find best practice for microplastic analysis by reducing time demand, human bias (false negative) and automatic identification bias (false positive and false negative) using spectroscopy (FTIR and Raman microscopy). The manual analysis under transmission mode, semi-automated method using ultrafast mapping and spectrum profiling, and automated method using ultrafast mapping, spectrum profiling and fully automatic identification were compapred. In the automated method, to check false positive rate during identification, all spectra were manually duble-checked after automated method have done. The automated method took the shortest time (3.2±0.5 h, which is occupied time by operator) to analyze whole filterpaper (Ø25 mm), but the polymer types were limited to the number of profile spectrums, fiber could not be detected, and the rate of false positive was 80±15%. While, semi-auto analytical method using spectrum profiling was suitable for microplastic analysis in all aspects. It took shorter time than those of manual analysis (manual: 6.1±0.8 h and semi-auto: 4.0±0.6 h), fiber could be distinguished by chemical and mapping image. And 22±12% (fasle negative) more microplastic particles were detected using semi-auto than using manual analysis. Two types of spectroscopic analysis (FTIR and Raman) for microplastics were compared in four different methods, manual identification in ATR and transmission mode and semi-auto method using FTIR, and manual using Raman. The analysis duration was overwhelmingly taken for long time (34 ± 1.5 h) in Raman followed by transmission (5.6 ± 0.3 h), ATR (4.8 ± 0.9 h) and semiauto (3.6 ± 0.5 h). However, the detected number of microplastics using Raman were 1.4, 1.9 and 3 times higher than using semiauto, transmission and ATR mode, respectively. And the range of 0-50 ㎛ was peaked in size distribution of Raman, but the range of 50-100 ㎛ was peaked in size distribution of the others. Depending on the microplastic size range of interest, it could be appropriate identification method.