Peaks in solvent blank

[Davidantony]

I am trying to devlope amethod for quinlones and sulfonamides in our xevo TQD LCMSMS.I am facing some problem in flumequin.In blank also there is a peak of flumequine coming.When iam injecting air blank also there is peak of flumequin comes under the same RT.It is probably from mobile phase.But when iam scan with mobile phase with the same combination of mobile phase with same ms condition there is no flumequine is there.I dont no from where this peak of flumequine comes in Blank

[Don_Hilton]

There are many possibilities. And one is that it may not even be flumequine.

What we don't know is the history of the instrument and column, the handling of materials in the lab. Nor dow we have any idea of what conditions you are using to elute or detect the flumequine.

On looking at a full scan as opposed to a single MS/MS transistion, the dewell time at any particular mass in full scan will be much less than in MS/MS - and spectral signals for weak peaks disappear into the background.

Possible source for the peak:
- poor needle wash, giving carryover,
- poor seal in the valves in the sampler resulting in carryover.
- accidental contamination of a solvent
- Junk in the solvents with a similar mass and fragmentation pathway to the target
- something coming off an old colulmn - or a column that needs to be more strongly rinsed at the end of a run.
- You could be runnign too close to the void volume with your peak

The list of guesses could go on for pages - more information is needed. And for figuring this out, unfortunately, this sounds like an exercise in patience and checking everything that goes into the instrument and changing conditions to see if this is a coeluting compund that can be resolved with a different column or gradient.

[shiva_kant]

I am trying to devlope amethod for quinlones and sulfonamides in our xevo TQD LCMSMS.I am facing some problem in flumequin.In blank also there is a peak of flumequine coming.When iam injecting air blank also there is peak of flumequin comes under the same RT.It is probably from mobile phase.But when iam scan with mobile phase with the same combination of mobile phase with same ms condition there is no flumequine is there.I dont no from where this peak of flumequine comes in Blank

david
I agreed with Hilton
Probability of contamination is in your HPLC part specifically needle, column, valves. As per your detail air blank also give pick and scan you are not gating flumequine pick. Its mean’s it is problem of carryover not solvent contamination because in case of solvent contamination you are gating pick in scane mode in mobile phase. You need to wash needle, column, and valves rigorously. And avoided higher con. injection.