Aliphatic petroleum Hydrocarbons by LC-MS/MS

[djletin]

I am working with some petroluem white oils (mineral oils) residue analysis in biolgical matrices. I am applying GC-MS (SIM) which works ok. However, my customorer who has a pharma background, but not analytical experience, insists that I use LC-MS/MS since that's what phrama uses in ADME studies to track drugs and metabolites. I've tried explaining that aliphatic HCs have no ionizable moiety so LC-MS won't work but he continues to insist tandem MS is the way to go. Could some one please confirm that n- and iso- alkanes won't ionize in LC-MS systems?

[sassman]

APPI and APCI are better than ESI, but you will be much better off using GC/MS for petroleum oils. LC/MS is much more sensitive for more polar compounds. Since you are extracting from biological matrices, all of those polar compounds from the organism will be in your sample and will cause much noise in your analysis. Also GC/MS is much less expensive to run.