Chromatography Forum

Our university is planning to buy a GCxGC system . I have some experience with GC-Q (Shimadzu 2010Plus and Agilent 7890/7000QQQ) to analyze unknown sample, and sometimes with very complicated mixture it's very hard to different compounds in overlapping peak. So I think, GCxGC can be helpful. The question is - what type of MS-detector prefer? As I know, the advantage of TOF-MS (Leco Pegasus eq.) is wide m/z window at high scanning speed (500-800m/z at 500Hz scans; at Shimadzu 2010Ultra - 200m/z@100Hz), and no skewing. What about GCxGC-TOF drawbacks (compared to GCxGC-Q)? Can I still use conventional mass-spectra library (NIST-08), which I use with GC-Q already, of I must buy special TOF-library? Is sensitivity of TOF comparable with Q? Or the only drawback is a high price? It will be very helpful, if someone with practical experience can answer me.

GC-TOF (Pegasus) definetly has advantages when we are speaking about unknowns (constant spectrum across the peak, high scan rate, powerful deconvolution software and high sensitivity in full scan mode (comparable with GC-QMS)), another advantage is very robust ion source, but if you are going to analyze compounds with m/z higher than 300, than you will find out that the sensitivity towards ions with high m/z is very poor, and the spectra are not "classic" in high m/z region. That is the main problems of Pegasus.

As for libraries: Leco uses the same libraries as other vendors (NIST, Wiley and so on).

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Can you please describe your "very complicated mixtures" in terms of sample mixture origin and compound types.
This may affect some answers
In our university "they" analyze mostly simple mixtures of organic reaction products.
Amirav

xjnrbqgfwfy
Can you please describe your "very complicated mixtures" in terms of sample mixture origin and compound types.
This may affect some answers
In our university "they" analyze mostly simple mixtures of organic reaction products.
Amirav

Usually it is a research work (eg, analysis of the products of enzymatic oxidation of phenolic compounds and lignin, analysis of the products of rocket fuel transformation in the soil) or qualitative analysis of samples of unknown composition from the MOE, or other laboratories (for example - to determine the qualitative composition of the substance of the barrels, that was found by MOE on the bank of the river, or determine the source of unpleasant odor near the plant). For routine analysis (FAME, phenols in water) we use gas chromatograph with conventional detectors (FID, ECD) and GC-MS (Shimadzu QP2010Plus).