Dear colleagues,
The new APGC (Atmospheric pressure gas chromatrography) ion source is a new alternative to the conventional EI (in that it provides soft, APCI-like ionization) for GC-MS.
I would like to learn more regarding:
1. Would you mind sharing your experience on the APGC ion source?
2. For routine metabolomics work, Would you recommend the coupling of a GC to Triple quad MS/MS or QTOF MS/MS?
3. There is currently no database for APGC spectra searches (e.g. as the conventional NIST database is for EI-based spectra). If I am to use a APGC-Triple quad MS/MS system, would it be a challenge to identify the different metabolites (as the mass accuracy or resolution of Triple quad is low)? Any ideas?
Thank you very much!
Hi Kay,
we've been using APCI hyphenated to a GC for almost a year now. It works great, when you do everything right... that means, the voltage settings are cruicial when setting up the source and the ion pathway. We also use additives to improve ionization and to provide internal calibrands. We don't do metabolomics, but for our samples, which range from very polar to apolar, the ion source is able to ionize almost everything (exept non-functionalized hydrocarbons). The choice of additive determines the upper ionization energy limit of your analytes, meaning, that if you choose an additive which exhibits an ionization energy of 9.5 eV all the analytes you will be able to detect will possess an ionization energy of less than 9.5 eV. As for your desire to identify unknowns, i would go for the higher resolving MS with MS/MS capabilities. The lack of source induced fragmentation can then be countered by controlled CID-experiments and the ability to determine the molecular formula.
Good luck!
Marius
Hi Kay,
My complete work is based both in metabolomics by using GC-APCI-QTOF and target analysis using GC-APCI-QqQMS/MS. The source works fine, but you have to take into account that due to the low fragmentation and the characteristics of the source, for most of compounds there is an equilibrium between the M+· and the [M+H]+ ion, which you can try to shift by adding modifiers to the source.
For metabolomics I would strongly recomend QTOF as you have exact mass. If your QTOF is a Waters Xevo G2 you can either look at the HE function, to have richer spectra.
Here is a paper of our group, elucidation making use of the HE function is very well explained in fig 1. http://www.ncbi.nlm.nih.gov/pubmed/24828980
Good luck!!,
Carlos
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Physical Phenomena
- Luminescence
- Fluorescence