The column used was a poly(ethylene glycol) diacrylate (PEGDA) monolithic capillary column fabricated using UV polymerization. Table 1 lists the column dimensions and reagent composition (i.e., amount of monomer, ratio of porogens, etc.) for the monolith. Details of the monolith fabrication have been published elsewhere [36,37]. The mobile phase composition used was 98% water in acetonitrile (v/v) for determining the extra-column variance of the injection valve using a non-retained analyte (uracil, 0.2mg/mL). The mobile phase flow rates used in this study covered the range of 0.05–0.4