Hello,
I am wondering if anyone has encountered the following problem with ion trap GC-MS: I'm trying to develop a GC-MS method to determine methylmercury, that I've either ethylated or phenylated, to produce methylethylmercury or methylphenylmercury. The problem is that as I want to do isotope dilution analysis of these compounds, then the instrument must return very accurate isotope patterns based on the 7 isotopes of mercury. The Varian Saturn GC/MS/MS trap I'm using, in scan mode, as I've nothing else, consistently gives incorrect isotope ratios that also vary across peaks. Injecting less analyte has no effect, though I remember that the carrier gas flow rate is critical for the trap to function correctly. An engineer from Varian has told me that the flow rate is set as it should be. Could there be any part of the trap that is in need of particular attention when cleaning? I have been told that ion traps are not famed for there mass accuracy (is this true?) but this is quite ridiculous. Any suggestion/help/advice will be gratefully accepted. Thanks.