Electron ionization (EI) mass spectra are widely used for the structural annotation of small molecules through comparison of experimentally acquired spectra with mass spectral libraries. EI is the most common ionization method coupled with gas chromatography -mass spectrometry (GC-MS). However, there is a lack of EI high-resolution mass spectral libraries available, especially for environmental chemicals . Additionally, spectra acquired using highresolution time-of-flight (TOF) and Orbitrap instruments differ from those obtained through low-resolution single quadrupole instruments. The disparity leads to relatively lower match scores when comparing high-resolution spectra to nominal mass spectra, limiting the applicability of those libraries . Compounding this challenge, many chemicals are not readily available commercially, and existing experimental libraries exhibit limited chemical diversity.