By Anonymous on Wednesday, August 20, 2003 - 04:35 am:
I would like to know more about the adduct formation in LCMS and details.
Can anybody give me some suggestion about this
subject.
Advance thanks
Anonymous
By M_Gardner on Wednesday, August 20, 2003 - 07:47 am:
Adducts form all the time, and often you want this to happen. If you're trying to make positive ions in electrospray, you usually want to form proton (H+) adducts, and you help this along by adding a little bit of acid to your mobile phase. Often when people say "adduct formation", they are talking about adducts other than H+ (e.g. Na+, K+) that may form as a result of LC system contamination. These can split your signal between e.g. H+ and Na+ and this is usually undesirable. Alkali metal adducts may also fragment differently from H+ adducts. Some neutral compounds won't readily form H+ adducts in electrospray, and one option is to add Na+ or NH4+ salts, and allow the analyte to form adducts with those cations. In negative ESI, we usually want to deprotonate the analyte to yield (M-H)-, but it is possible to form adducts in negative mode as well. I don't have the names of any review papers in front of me right now, although I'm sure you can find many on the subject. Here are a couple of general books on LC/MS to get you started.
W.M.A. Niessen. Liquid Chromatography-Mass Spectrometry, 2nd edition. Marcel Dekker Inc., New York, 1999.
Electrospray Ionization Mass Spectrometry. R.B. Cole (ed.); John Wiley and Sons, Inc., 1997.