Sample of BTB from port #4 is perfused through the sorbent via port #2, where it is retained in protonated (yellow) form. Next alkaline MeOH eluant (port #5) is perfused through the microcolumn via port #2. Deprotonated BTB (blue) is eluted.
Flow reversal removes sorbent from microcolumn. Forward flow re packs OASIS HLB beads which are reliable held in place by green optical fiber.