For the performance assessment, the test set was used. In this instance, TN cases were also generated based on the mono-iso pairs from the test set with a random mass error added to the isotopologue mass of 0.01 to 1 Da. For both the TP and TN cases, the score EM D s were calculated (Equation ). To select a suitable score EM D cut-off value and assess the performance of the classification model, the TP and false positive (FP) rates were calculated for a range of score EM D values. The scores EM D fromm 0.7 to 1 Da with a step size of 0.002 Da were employed to calculate the TP r and FP r (Equation 8 and 9, respectively). Here, the TPs equal the number of cases from the test set that were correctly classified as an isotopologue, FNs are the number of cases that were incorrectly classified as not an isotopologue, TNs are cases that were correctly classified as not an isotopologue, and FPs are the that were wrongly classified as isotopologues.