Re: MRM giving Double Peaks
Posted: Wed Jan 11, 2012 7:01 am
First thing that struck me is that you are injecting 10ug/ml (10,000ng/ml) onto a narrow bore column.
This is a HUGE amount! What volume is your injection?
Try a lower concentration. Does the problem persist?
If so, is it the same ratio (peak height/peak height)?
You said you have sample prep'd in the T0 mobilephase. This is good.
Did you look for a confirmation transition?
I see from your images that the parent peak is 753.3 but I do not see the fragment ion.
You can look for another fragment ion of your compound. Then run both transitions in your scan 753.3.x and 753.3 > y.
If the ratios of the responses of these two transitions are different in the two peaks you have a contamination that has the same mass transition(s).
That you only see this in one type of scan...
"Interesting thing is that the MS2 Fullscan method comes up with only 1 peak."
is strange. It looks like to me that you do in fact have 2 peaks eluting. I am unfamiliar with the scan modes of the system you are using.
Are the retention times of the "contamination peak" consistent?
This is a HUGE amount! What volume is your injection?
Try a lower concentration. Does the problem persist?
If so, is it the same ratio (peak height/peak height)?
You said you have sample prep'd in the T0 mobilephase. This is good.
Did you look for a confirmation transition?
I see from your images that the parent peak is 753.3 but I do not see the fragment ion.
You can look for another fragment ion of your compound. Then run both transitions in your scan 753.3.x and 753.3 > y.
If the ratios of the responses of these two transitions are different in the two peaks you have a contamination that has the same mass transition(s).
That you only see this in one type of scan...
"Interesting thing is that the MS2 Fullscan method comes up with only 1 peak."
is strange. It looks like to me that you do in fact have 2 peaks eluting. I am unfamiliar with the scan modes of the system you are using.
Are the retention times of the "contamination peak" consistent?