****************************************************************************** From: Elliot Rachlin Date: Wed, 4 Nov 1998 11:09:35 -0700 Subject: Electrospray of cobalamins Organization: * We are doing electrospray analyses of cobalamins on a Micromass Quattro II. The samples are dissolved in acetonitrile and water (1:1) and infused into the instrument at 10ul/min. The spectra show large ions at 22 mass units higher than the molecular ions suggesting the presence of sodium. Is sodium contamination typical in the electrospray spectra of cobalamins? Also, can you suggest ways to remove sodium and other salts prior to electrospray analyses? I would appreciate any assistance you can provide. Thank you. Elliot Rachlin ****************************************************************************** From: William Cotham Date: Wed, 04 Nov 1998 14:54:06 -0500 Subject: Re: Electrospray of cobalamins Organization: Univ. of South Carolina, Columbia Elliot Sodium contamination can be a big problem in electrospray analysis. I don't know the history of your sample, but try to keep all solvents and samples away from glass. use plastic ware whenever you can. Sometimes its easier trying to avoid salt contamination than removing it. If you need to remove the sodium before analysis, then try a short C18 LC column in line with your mobile phase. This should retain your analyte slightly while the salts elute in the void volume. -- William E. Cotham, Ph.D. Mass Spectrometry Laboratory Dept. of Chemistry & Biochemistry University of South Carolina Columbia, SC 29208 Phone: (803) 777-2039 FAX : (803) 777-9521 ****************************************************************************** From: wuytens@my-dejanews.com Date: Thu, 05 Nov 1998 08:59:31 GMT Subject: Re: Electrospray of cobalamins Organization: Deja News - The Leader in Internet Discussion Hi, 'Sodium contamination' is almost always present in ESI-spectra. If you really want to get rid of it, you most clean your source thouroughly, watch the quality of your water, be prepared to change your tubing and process your samples over a SCX (Strong Cation Exchange) cartridge (Baker, Waters or other suppliers). Rather then taking all these efforts, it's easier to use these clusters as an advantage : if you add a little NH4OAc (.02 M or less) to your solution, you should see a shift of 5 amu, because the NH4-ions compete with the Na-ions to form clusters. The addition of NH4+ has the advantage that you control in this way the formation of clusters and leaves you independent of the sample composition (regarding ions). By the way, some molecules have indeed a strong tendency to produce Na-adducts : glucosides for instance are major 'sodium absorbers', in fact (should anyone else read this), I've got the impression that the number of hydroxyl-groups is a measurement for the ability to form Na-clusters. Greetings & Good luck Bart Wuytens -----------== Posted via Deja News, The Discussion Network ==---------- http://www.dejanews.com/ Search, Read, Discuss, or Start Your Own ****************************************************************************** From: "Daniel Boismenu" Date: Fri, 6 Nov 1998 13:53:58 -0500 Subject: Re: Electrospray of cobalamins Organization: McGill University Computing Centre You did not reveal the provenance of your samples. If they are from a biological source, it would be odd that you would not get a sodium adduct, taking in mind the amount of sodium that is found in living cells. The sodium of the M+Na ion could originate from the sample itself, or from contaminated HPLC water. To verify that your HPLC system is not the sodium source, I suggest to run a pure standard known to be sodium free and look at the relative intensity of the M+H and the M+Na ions. If the M+Na intensity is still very high, check your water. When in doubt, always use the highest water quality, such as nanopure water and never allow the water to contact glass. It is well known that sodium leeching out of glass is enough to totally suppress the phosphate signal of RNA and DNA. So, if your analyte has a strong affinity for sodium, you would not help yourself by using sodium contaminated water. For desalting your sample, dialysis is out of question, because of a too low molecular mass. The easiest way to desalt it would be to do HPLC-MS. Inject your sample on an appropriate column, then wash the sample for several minutes with the highest quality of water, then elute the analyte with acetonitrile or methanol. Another way to do it is to put C18 material in a gel loader tip and use it as a desalting device. You could wash out the salts with pure water and then recover your sample in a few microliters of an organic solvent water mixture containing formic acid. You will have to find out which would give the optimal recovery between methanol-water or acetonitrile-water, and what would be the optimal solvent to water ratio (50:50, 70:30, 90:10). You will have also to play on the concentration of formic acid to use (0.5%, 1%, 2%). Sincerely, Daniel Boismenu, Ph.D. Biomedical Mass Spectrometry Unit McGill University 1130 Pine Avenue West Montréal, Québec Canada H3A 1A3 Tel (514) 398-3661 Fax (514) 398-2488 MCDL@MUSICA.MCGILL.CA