We use a SIFT-MS for analysis of breath samples from patients. However, much of the research literature has been using GC-MS. Can the concentrations of products found in GC-MS analysis be accurately compared to our SIFT-MS? Or is some sort of calibration of those specific machines necessasry prior to comparison?
Florian Obersteiner
I'm definitely not an expert in this field, hence the question. But yes, the machines are independently calibrated to a known gas, and must detect them within a narrow margin of error. So, I hope that the results are comparable. But SIFT uses multiple reagents for ionisation, so I wondered whether produces varying mass/charge, compared to GC-MS. I agree though, if a machine is measuring a concentration in a sample and that has been calibrated to a known gas, then it should be comparable to any other machine, regardless of type of analysis...hopefully.
Thanks Florian Obersteiner
. Even with complete trust, there are many differences that could make the comparisons difficult: sample collection technique, time to analysis, environmental factors, etc. But good to have someone to talk things over, someone who has more experience than me that is.
Hi Ravi,
the answer is : NO
Justification: GC/MS usually uses EI (electron ionization). This process generates OE+-ions (radical cations). SIFT is a kind of chemical ionization that produces EE+-ions. Both kinds of ions show different fragmentation processes.
Regards
Markus
P.S.: The answer changes to YES if your GC/MS-system uses CI as ionization method.
P.S.: My answer refers only to the comparison of mass spectra.
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