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sodiated ion
Posted: Sat Jul 16, 2005 2:31 pm
by gurmeet
Hi,
Iam new to LC/MS/MS. I am facing a problem that my analyte peak is comming at 441 instead of its actual 418. All the glassware iam using is A grade & i wonder if it is comming from glass. Can somebody help?
Posted: Mon Jul 18, 2005 2:12 pm
by bert
Are you using electrospray or APCI, and what ionisation mode (positive or negative)??
Reference on Internet
Posted: Mon Jul 18, 2005 10:48 pm
by james little
Can be a really agravating problem. On my instrument (Waters Quads and LCT, etc), the M+Na adduct is a function of the cone voltage (DP on a Sciex). At higher cone voltages, the M+H and M+NH4 ions decrease, the fragments from M+H and M+NH4 increase, and the M+Na increases. Thus might try plotting the ions of interest vs cone voltage.
We usually run with 2.5-10 mmolar ammonium acetate or 10 mmolar ammonium formate adjusted to pH of 3.5 with formic acid.
Also some information on adduct formation is found in the following document on the internet..
http://www.gtfch.org/tk/tk71_2/Lambert.pdf
sodiated ion
Posted: Tue Jul 19, 2005 1:22 pm
by gurmeet
Sir,
Thanx for your consideration, iam using Turbo ion spray (ESI) in Positive mode. I could not understand the source of sodium ion in my analyte.
-gurmeet
Posted: Tue Jul 19, 2005 1:41 pm
by bert
If you expect your peak at 418, does this mean that your molecular weight is 417? In that case wouldn't you expect that a sodium adduct [M+Na]+ would give response at 440.
sodiated ion
Posted: Wed Jul 20, 2005 11:38 am
by gurmeet
I have got my problem solved using APCI, my molecular mass was 418.4 & now iam getting good signal at 419.4.
Thanx for your timely help.
-gurmeet