Table shows the effect of fingerprint screening in substructure search for PFAS Definitions A, B and C across the two compound datasets (CORE and Patents). It is interesting to note that the combined use of fingerprint selection and subsequent substructure search on the selected list resulted in quite comparable results for all the chemistry toolkits when using the higher quality CORE dataset. The number of identified PFAS is the same for CDK and OCL, slightly lower for RDKit. The CDK fingerprint selection appears to be more efficient than using the OCL or RDKit fingerprints for PFAS Definition A and B. For the more strict Definition C, OCL fingerprints are most selective. Not surprising is the lower number of identified PFAS for the more heterogeneous patent SMILES dataset, since more molecules are sorted out by the RDKit parser as shown in Table .