Clarus 500 & selective ion monitoring

[rambiochem]

Can anybody tell, is it possible to do selective ion monitoring using PE Clarus 500 GC-MS?

[djletin]

Yes. It is referred to as single ion recording (SIR) but is essentially the same as SIM

[rambiochem]

Is it same as searching the traces in TIC? I mean, would the chromatogram of traced mass and that obtained by SIM be the same?

[djletin]

I am not sure what you mean by "searching the traces in TIC". Generally "searching" against an MS library is done in full SCAN mode where all the masses are aquired, say between 50 and 400 m/z. Generally used for identification of unknows. SIM or SIR is used for quantitative anlysis where you know what you want to quantify and identification is based on the Single ion "monitored" or "recorded" plus one or two add'l quanlifer ions. Since both SIM and SIR only "look for" a copule of ions at a time, it is much more seneditive than SCAN mode.

Bottom line, for practical purposes SIM and SIR are equivalent functions in almost all aspects.