I tried using a small amount of qiagen tip 20 resin in batch-mode for PCR product purification (equilibrate-bind-wash-elute, can't use silica spin columns for various reasons). Binding was near complete (no detectable DNA in flow-through), but elution was very poor (less than 20%). I normally get 80% recovery with silica-based qiagen columns, but q tips are DEAE-based, i.e.they supposedly work as an anion exchanger. I wonder if there is a way to get more DNA out of them w/o denaturing the DNA. Qiagen claims density of their DEAE is much higher than normal DEAE exchangers. By the look for the beads, the matrix still appears to be silica or polystyrene (settles very quickly, simliar to POROS beads. I wonder if this resin works in a mixed way (DEAE, plus hydrphobic effects on silica/plastic).
Did you concentrate the eluate by precipitation with isopropanol before checking the yield? For what it's worth, if the PCR fragment is small enough it might not be precipitated as efficiently as larger DNA fragments such as plasmids, etc.
Alehandro -- I measured the yield without the precipitation; the input and output volumes were the same.
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