I am getting low coupling efficiency with amidites. Do you have any suggestions on how to improve it?

There are two factors that can affect the coupling efficiency of amidites, which are coupling time and dryness of the acetonitrile. It may be helpful to increase the coupling time and allow the reaction more time to complete. We recommend pre-treating the acetonitrile with molecular sieves prior to adding it to the amidite. The acetonitrile must be anhydrous to ensure amidite coupling.