Comparison of reference libraries for the detection of tire-derived microplastics (TMPs)

Introducing microplastics (MPs) into the marine environment is a global problem. Tire-derived microplastics (TMPs) are estimated to account for 60% of all secondary MPs dispersed in aquatic environments. To effectively detect TMPs in environmental samples using micro-Fourier transform infrared (μFTIR) spectroscopy, a high-quality reference library is essential. However, the use of conventional diamond crystals in FTIR presents challenges for the detection of materials containing carbon black, such as rubber and tires. In addition, there is a discrepancy between spectra from standard libraries and spectra from environmental samples, which makes detection difficult. In order to overcome these problems in the detection of TMPs by μFTIR, we developed four reference libraries to improve the detection, and 'The 26 tire wear library' was found to be the best among these four. Furthermore, a comparison of these new libraries revealed the following requirements to improve TMP detection: (i) the reference spectra must be acquired under the same setup used for material observation including prism material, (ii) tires, not rubber, must be used as reference materials, and (iii) tire wear samples must be prepared to replicate the actual generation conditions on roads.