3D Conformer generation Molecular structures and other metadata, e.g., ChemOnt chemical class , were extracted from the RECETOX Exposome HR-[EI+]-MS library in SDF using the RDKIT package . Subsequently, three-dimensional conformers were created from simplified molecular input line entry system (SMILES) descriptors using a customized variant of the rdconf code (see rdconf.py), which leverages RDKIT functions while employing the universal force field (UFF) method. Molecular structures were optimized using GAMESS at the 6-31G level of theory and gradient convergence tolerance of 5 × 10 -4 prior to QCxMS analysis. Spectra prediction using QCxMS QCxMS calculations were performed using default parameters (electron energy: 70 eV; excess energy: 0.6 eV/atom; initial temperature: 500 K; simulation time: 10 ps). The ground state trajectories and production runs were performed using the SQM GFN1-xTB method. After fragmentation, the ionization energies (IEs) were calculated using GFN1-xTB, and the fragment with the lowest IE obtained the positive charge. Default number of trajectories were computed (25x the number of atoms in the molecule) for every molecule.