Determination of the solvent(s) most suitable for C18 dSPE-based lipid depletion and LMWM profile preservation required empirical assessment. Acet, MeCN, IPA, MeOH, and EtOH were tested owing to their routine use in LC-MS workflows. For each set of solvent conditions, the residual lipid profiles were analyzed by C8 RPC+ and visually inspected (Figure ). IPA and Acet failed to adequately deplete the lipids present, owing to their efficient disruption of lipid-to-sorbent binding. The remaining solvents tested (MeCN, MeOH, EtOH) resulted in greater lipid depletion, especially for more hydrophobic lipid species (e.g. two and three acyl chain lipids predominant in chromatographic regions 2 and 3). In all conditions tested, the less hydrophobic lipid species (e.g. lysophospholipids predominant in chromatographic region 1) were the least affected by depletion. This is desirable, as this region may contain important LMWMs including lipophilic xenobiotics and endogenous metabolites (e.g. bile acids and acylcarnitines). The effects of MeCN, MeOH, and EtOH solvents (individually, in pairwise volumetric 1:1 combination and altogether) on the resulting LMWM profiles were assessed using C18 RPC+/-analyses. Solvent compositions containing EtOH produced the highest number of features, but also produced a higher baseline and large asymmetrical macromolecule-derived peaks which eluted from seven minutes onward (Figure .A), ultimately resulting in carryover and increased system pressure during sequential injections. The same effects were observed to a lesser extent with the other EtOH and MeOH solvent compositions. It was hypothesized that the combination of water and these alcohols was not sufficient in reducing the dielectric constant, allowing proteins to remain in solution.