By Oscare on Wednesday, February 25, 2004 - 12:41 pm:
I'm using a DEAE column to separate oligonucleotides (15mer - 80mer). I have achieved good recoveries and separarison with A: 20 mM Tris-HCl, pH 8.5 and B: A + 2 M ammnonium acetate (NH4Ac). Samples are recoveres in about 1.5-2 ml.
I have tried to remove the NH4Ac by vacuum with a spin-vac (~20 torr -not so sure-, 40 C) without success.
Any input on this will be greatly appreciated.
Thanks,
OZ
By Anonymous on Thursday, February 26, 2004 - 06:37 am:
Ammonium acetate in aqueous solution is not really volatile.
By Anonymous on Thursday, February 26, 2004 - 06:30 pm:
I donow. We use ammoniumacetate in MS all the time.
By MG on Friday, February 27, 2004 - 12:39 pm:
Sure, but with LC/MS, the source is usually heated to 300°C or greater.
By Jim Thayer on Friday, February 27, 2004 - 03:51 pm:
Dear OZ,
Removal of NH4OAc eluents to aid recovery of oligonucleotides is possible, but requires very many cycles of Speed-Vac treatment, during which your oligos could decompose. I have used several methods after purifying oligos on a DNAPac PA100 column (Dionex). If I were in your shoes, I would probably use BioGel P60 chromatography to exchange the buffer, or ice-cold ethanol extraction to precipitate the oligos 20 bases and up, and the Sep-Pak C18 method for shorter oligos (See "Molecular Cloning: A Laboratory Manual" by Sambrook Fritsch and Maniatis). I have the second edition where the procedures are described in book 2 on pages 11.34, 11.37, and 11.39.
I hope this helps,
Jim Thayer
Dionex Corporation