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- Posts: 1
- Joined: Wed Apr 10, 2013 12:29 pm
I am working with LTQ XL (ESI) and have a very low sensitivity (cannot see the standard (resveratrol) even at 2.5 mg/ml).
The only thing which I have found wrong is that spray current is more than 5uA and not stable with more than 80% of water. But my standards (resveratrol and metabolites) are eluting from 20% to 40% ACN (acetonitrile). The spray current is changing from 5 to 0.1 uA when the gradient changes from 20% to 100% of ACN.
My parameters:
Spray voltage 4 kV
Flow rate 300 ul/min
Sheath gas 50 arb
Aux gas 5 arb
Capillary temperature 350 C
Solvents water-acetonitrile (0,1% formic acid) LCMS-grade.
Position C, 1.5 micrometer
I have changed fused silica and ESI needle - it didn’t help. And of course I made as good tune file as I can. No leakage is observed.
The baseline of PDA detector is drifting negative, so that I cannot see anything at all. But it should not have influence on MS part, right?
Could anyone please help me with the problem?
The only thing which I have found wrong is that spray current is more than 5uA and not stable with more than 80% of water. But my standards (resveratrol and metabolites) are eluting from 20% to 40% ACN (acetonitrile). The spray current is changing from 5 to 0.1 uA when the gradient changes from 20% to 100% of ACN.
My parameters:
Spray voltage 4 kV
Flow rate 300 ul/min
Sheath gas 50 arb
Aux gas 5 arb
Capillary temperature 350 C
Solvents water-acetonitrile (0,1% formic acid) LCMS-grade.
Position C, 1.5 micrometer
I have changed fused silica and ESI needle - it didn’t help. And of course I made as good tune file as I can. No leakage is observed.
The baseline of PDA detector is drifting negative, so that I cannot see anything at all. But it should not have influence on MS part, right?
Could anyone please help me with the problem?
