sodiated ion

[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?

[bert]

Are you using electrospray or APCI, and what ionisation mode (positive or negative)??

[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

[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

[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.

[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