Ontwsep™ C8 is a reverse phase C8 extraction cartridge made from high-purity spherical silica gel. Its adsorption capability is similar to that of C18, with non-polar carbon bond interactions playing a major role. However, because C8 has a shorter carbon chain than C18, its retention of non-polar chemicals is weaker, making it easier to elute samples with strong non-polar adsorption. It can extract both fatsoluble and water-soluble vitamins from plasma and is frequently used to desalt biological macromolecule samples.