Polyacrylamide gel electrophoresis (PAGE) purification works well for longer oligonucleotides (>45-50 bases) that do not resolve well on HPLC. There are some conjugations that require PAGE because of purification issues on HPLC. We also use PAGE under sterile conditions for RNA. The yields are lower with PAGE and it is also limited in scale because of expense, but in many cases it will result in the highest quality product. Related Article(s) When is my Oligonucleotide Pure Enough?