I started using a ‘borrowed’ 6530 Agilent QTOF but I‘m afraid I still lack practical knowledge with it. I’m more used to the Thermo’s Q-Exactive and I feel like Thermo‘s acquisition software has more parameters to be optimized.
So, anyone have any experience to share, regarding CID voltages, threshold values, acquisition rate, source parameters (for the DualESI source), fragmentor....?
thanks
Hello Ricardo,
could you be more detailed with your question? It would be helpful to know which type of analytes you're analyzing or what type of chromatographic method you're using
Of course Michel Gunnar Kather ! I’m using a Zorbax extended-C18 2.1x50 mm 1.8 um for chemical profile of different samples; for metabolomics. So I have different compounds among Natural Products and I’m mainly using an exploratory linear gradient of methanol in water (0.1% formic acid).
What is bothering me is the low intensity of peaks (but I’m still exploring different buffers such as 5 mmol/L ammonium acetate and 0.1 % formic acid) and the collision energy. It seems to me that this Q-TOF needs higher energy (than I was used to) at CID for fragmentation.
My MS method:
Source – DualESI; gas temp: 350oC; Drying gas: 11 l/min; Nebulizer: 25 psi; Fragmentator 240 V; Skimmer: 65 V; Oct 1 RF Vpp: 750 V; VCap: 3500V
Acquisition: Auto MS/MS
Range (MS and MS/MS): 110 – 1700; Acquisition rate: 2 spectra/seg; Isolation Width: Medium (~4 m/z);
Colision Energy: 35 and 50; 3 Max precursor Per Cycle; Precursor Threshold: 5000 counts; Enable exclusion after 2 spectra and release after 0.8 min.
Thank you!
I have a few ideas from where your intensity problems might originate.
First off, for metabolomics analysis your fragmentor voltage is way too high. I am working with an Agilent 6520 QTOF and the only difference between the one you are using and the one i am using is that your device is equipped with an Agilent JetStream ion source (which in general, improves ionisation and thus signal intensities).
So if i were to start from scratch, for a metabolomics approach i would reduce the fragmentor voltage to 100 V or 150 V (or something in between, depends on the type of analytes). At 240 V i would expect a lot of in-source fragmentation. For good fragmentation results, for most small molecules CID voltages between 10 and 40 V should be sufficient (e.g. Metlin database uses 10, 20 and 40 V). You didn't mention the sheath gas temperature and sheath gas flow. Agilent recommends that the sheath gas temperature should be 50 °C above the drying gas temperature
I totally agree with Michel Gunnar Kather. A fragmentor voltage of 240 V is way too high. After reduction you will most likely see more precursors due to less pronounced in-source fragmentation.
Did you run a QTOF Mass Calibration?
I do agree with the fragmentor being too high, but I used 110V before and I issue remained the same. I’ll look better into it and on the sheath gas temperature.
thanks
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