contribution are reported for each factor. Percentage contribution was calculated by dividing each calculated factor variance by the sum of all variances. This measurement gives insight into which factor contributes the most to the overall extraction and which factors have little to no influence. This information is important as it can guide inferences based on the main effects plots. For RP(+) number of features, extraction solvent had the largest percent contribution at 73.3%, followed by volume at 21.9%, time at 4.4%, and reconstitution solvent having the lowest contribution at 0.4%. This is consistent with the observations made in the PCA plot (Figure ), where separation along the PC-1 axis was associated with different extraction solvents, and the main effects plot (Figure ), where extraction solvent and volume datapoints deviated furthest from the grand mean line. A summary of percent contributions calculated from the ANOVA tables for all other MS conditions can be found in Supplemental Figure . Overall, the extraction solvent had the largest percent contribution on the first round RP extraction, while volume had the largest contribution to the second round HILIC extraction. This observation emphasizes the need for appropriate volume considerations when performing a sequential extraction due to the potential chemical overlap between extraction rounds or when conducting quantitative measurements where the concentration can be underestimated at low volumes.