In the last decades the pollution of the oceans with plastic particles smaller than 5 mm, called microplastics is moving into the focus of science and governments. The determination of microplastics includes several steps starting with sampling, work up and finally analysis. In recent studies with µFTIR microscopy was found as a powerful tool allowing the analysis of complete filters. The measurement is performed mostly by the spectrometer, while the data interpretation had to be made by hand based on false color images. We developed a novel approach to overcome the manual analysis and therefore decrease the high time demand for analysis of microplastics. It was possible to analyze measurement files containing up to 1.8 million single spectra by library searches against an optimized database of different synthetic and natural polymers. The accuracy and data quality was monitored by benchmark tests. The high quality data generated allowed image analysis, giving information for the particle size distribution for each polymer type as well as their distri- bution on the filter. All data was collected with relative ease even for complex sample matrices. This approach has significantly decreased the time demand for the interpretation of FTIR-imaging data and increased the generated data quality.