The phosphoramidite of diethylene glycol monoethyl ether, UniCap, is the basis for an alternative capping reagent. To use UniCap as a capping amidite on the Expedite 8909 or AB synthesizers, dilute it to the standard amidite concentration and place the vial in position 5 on the instrument. Cycles can be modified by adding coupling steps for amidite reservoir 5 after the last column coupling step. The standard capping steps can be left out of the cycle. UniCap Phosphoramidite was originally developed for oligo synthesis on the surface of chips and is the capping reagent of choice for this application.
Coupling: For capping, add as a second coupling step after base coupling using standard coupling conditions.
Deprotection: No changes needed from standard method recommended by synthesizer manufacturer.