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- Posts: 13
- Joined: Wed Oct 01, 2014 6:09 pm
Hi all,
We have a thermal finnigan deca instrument. I got high intensity noise problem during LC-MS/MS method development.
This is what I did so far. All the ionization and fragmentation parameters were optimized during MS direct infusion experiment. When I switched to the LCMS experiment, I got good signal/noise for analyte peak when I ran LC-MS (SIM) while that was not the case for LC-MS/MS. I observed high intensity background noise and almost no noticeable analyte peak during LC-MS/MS. I have cleaned the MS down to the trap part. I was thinking the problem should not come from the contamination. I have also tried to tighten the screw for the helium inlet part again. Are there any other parts I should check again in case that the problem was coming from some faulty parts? Or I still should focus on the parameter optimization?
Here is a list of noise intensity I obtained for comparison:
MS Direct infusion:
MS (Scan): E1-E2 MS/MS (Scan): E1
LC-MS:
LC-MS (Scan): E5 [mass range: 50-500] E4 [mass range: 500-2000]
LC-MS (SIM): E2
LC-MS/MS
LC-MS/MS (Scan): E4 LC-MS/MS (SRM): E3
Parameters for LC-MS/MS experiment:
Column: C18 4.6 mm x 250 mm
Flow rate: 0.5 ml/min
(I tried 0.2 ml/min. That doesn’t help to reduce the background noise during LC-MS/MS.)
Mobile phase: 0.1% formic acid in ACN : 0.1% formic acid in H2O = 38: 62
Spray voltage: 5 kV
Capillary temp: 300 C
Collision voltage: 10 V
Collision energy percentage: 35%
Additionally, I had another problem which is mass shifting (+1 amu) after I cleaned the ms. Is this a helium leaking problem or are there some other possible reasons?
Any suggestion will be greatly appreciated!
Here are some sample chromatograms:
LC-PDA vs. LC-MS (SIM)
LC-PDA vs. LC-MS/MS (SRM)
Thank you!
We have a thermal finnigan deca instrument. I got high intensity noise problem during LC-MS/MS method development.
This is what I did so far. All the ionization and fragmentation parameters were optimized during MS direct infusion experiment. When I switched to the LCMS experiment, I got good signal/noise for analyte peak when I ran LC-MS (SIM) while that was not the case for LC-MS/MS. I observed high intensity background noise and almost no noticeable analyte peak during LC-MS/MS. I have cleaned the MS down to the trap part. I was thinking the problem should not come from the contamination. I have also tried to tighten the screw for the helium inlet part again. Are there any other parts I should check again in case that the problem was coming from some faulty parts? Or I still should focus on the parameter optimization?
Here is a list of noise intensity I obtained for comparison:
MS Direct infusion:
MS (Scan): E1-E2 MS/MS (Scan): E1
LC-MS:
LC-MS (Scan): E5 [mass range: 50-500] E4 [mass range: 500-2000]
LC-MS (SIM): E2
LC-MS/MS
LC-MS/MS (Scan): E4 LC-MS/MS (SRM): E3
Parameters for LC-MS/MS experiment:
Column: C18 4.6 mm x 250 mm
Flow rate: 0.5 ml/min
(I tried 0.2 ml/min. That doesn’t help to reduce the background noise during LC-MS/MS.)
Mobile phase: 0.1% formic acid in ACN : 0.1% formic acid in H2O = 38: 62
Spray voltage: 5 kV
Capillary temp: 300 C
Collision voltage: 10 V
Collision energy percentage: 35%
Additionally, I had another problem which is mass shifting (+1 amu) after I cleaned the ms. Is this a helium leaking problem or are there some other possible reasons?
Any suggestion will be greatly appreciated!
Here are some sample chromatograms:
LC-PDA vs. LC-MS (SIM)
LC-PDA vs. LC-MS/MS (SRM)
Thank you!
