“…The cleanup step could be achieved by using single or multiple SPE with different sorbents (silica, polymer, or carbon-based), or combinations of these (mixed mode). 22 ) functional groups), Bond Elut C18 (C 18 hydrophobic silica-based encapped sorbent), Bond Elut Jr-PSA (anion exchange), Bond Elut Accucat, Bond Elut SCX (silica-based benzene sulphonic acid, nonendcapped), Strata-X-C (Polymeric resin functionalised with polar and strong cation exchange groups), Strata C18E (C 18 hydrophobic silica-based sorbent), Chromabond HR-XC (Polymeric resin functionalised with polar and strong cation exchange groups), Carbograph 4 (graphitised carbon), or Bakerbond SiOH (silica gel based sorbent), among others. Hydroxylated polystyrenedivinylbenzene copolymer phase (ENV+) gives the strongest retention.…”