Enamine retention time (EnamineRT) dataset. The LC-MS spectra were collected for the compounds produced at Enamine over the past year. Each spectrum was processed using an inhouse automated peak-to-compound assignment tool (see Figure ). Our standard LC-MS protocol includes the use of five detectors: two ultraviolet detectors (UVDs, at 216 and 254 nm, respectively), two MS detectors (for positive and negative ions), and an evaporative light scattering detector. The compounds characteristic RT values were based on UVDs due to their higher resolution and better peak quality, although the presence of the compound was confirmed by the MSDs. If a spectrum contained a single peak with the molecular ion of the expected compound, the retention time of that peak was designated as the compound retention time. Molecular ions or a few specific fragment ions were detected in both positive and negative MS detectors. Typically, MH + or MH -was considered as a molecular ion, but we also included other ions such as MH3O + and fragments such as M -tBu. In total, each single compound could be represented by up to 10 ions, which increased the likelihood of detecting the molecule if present, but also increased the risk of false positive detection.