Chromatography Forum

Hi,
I am trying to get some details on the advantage of using IT-ToF for metabolite analysis of low mass range (180-500). The matrix contain lower proportion of these LMW compounds and as I was searching through the literature it seems that IT-ToF offers better sensitivity to lower mass ions.

It is claimed that, the IT-ToF achieves this by changing the period of voltage pulses during the ion introduction into ToF. And based on the ion distribution this can be controlled to get higher sensitivities in all mass ranges.

Since I haven't used it IT-ToF at all, and I have very limited experience with QToF, I will greatly appreciate any help in deciding which instrument to go with. Also can a chromatographic separation prior to sample introduction give better sensitivity of low mass range in either of these detectors?

If you plan to buy such an expensive instrument, I would recommend that you send a mixture of representative compounds to both IT-TOF and QTOF manufacturers for a performance test. Sensitivity is not the only parameter to take into account when using a TOF instrument: resolution and mass accuracy are important as well.

More than sensitivity, the advantage I can see for IT-TOF is the possibility to perform MSn experiments with high mass accuracy on the product ions. Sensitivity might be slightly higher because the trap can increase the duty cycle. But other parts (like skimmers and ion guides) also play a role in the overall sensitivity of the instrument.

I think the resolution of the Shimadzu IT-TOF is about 10'000 and mass accuracy around 5 ppm. At least 4 companies sell QTOF with a resolution of 40'000 and mass accuracy below 2 ppm (Bruker, Waters, Agilent, ABSciex). So do you prefer MS/MS with 1ppm precision or MS3 capabilities with 5 ppm precision?