I am trying to separate oligonucleotides by HILIC (HILIC-MS more sensitive than IP-RP-MS). I have only a silica column (4.6*250 mm, 5um). I think oligonucleotide have strong retention on this column as a 20 mer primer did not elute with 50% water. I could not find any paper that separated oligonucleotides by bare silica. Did Anyone work in this field or any information about that?
At least 2-3% water is needed for HILIC mode. What is the maximum percent of water?
Thank you
You can use 100% water so long as the mobile phase is acidic or neutral. You may need a solvent modifier to elute the oligonucleotides.
What was your mobile phase? Acetonitrile, methanol? Something else? You may need to try diol or another bonded phase, too.
Maybe run in basic mobile phase to increase ionization of the oligonucleotide?
Michal Kriegelstein You wouldn't want a basic mobile phase for HILIC when using silica-based stationary phases (silica, diol, other bonded phases bonded to silica). Silica dissolves in polar basic mobile phase such as those used for HILIC. That's why I mentioned acidic or neutral mobile phases.
However, alumina HILIC can be run under basic conditions.
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