If a short hydroxyalkyl group is tolerated at the 5' terminus, FDMT-On Purification Modifier is an effective way to enable fluorous purification in a variety of applications without having to purchase a different fluorous amidite for each different 5' nucleobase. This phosphoramidite installs a fluorous dimethoxytrityl group via a short tether. After fluorous affinity purification and detritylation, a 3-hydroxy-1-methylpropyl group remains. FDMT-On Purification Modifier couples with greater than 95% efficiency (typically >98%) under the standard conditions recommended for popular synthesizers. If a 15 minute coupling is used instead, the efficiency rises to typically >99%. Please note that while this reagent is freely soluble in acetonitrile, it is somewhat slow to dissolve. Allow 30 minutes with occasional swirling for complete dissolution. After cleavage from the support and nucleobase deprotection using standard techniques, the fluorous-tagged oligonucleotide is purified using a Fluoro-Pak Column™ (FP7210 or FP7220) and Loading Buffer (LB7100). As usual, ammonia removal is not required, and detritylated oligonucleotides are obtained with high recovery, free from failure sequences.