Anyone heard of analyzing for Polysorbate or Tween by performing a liquid liquid extraction (hydrolysis) to obtain the singature fatty acid then analyze by LC MS in SIM?

I have tried this, but can not obtain a clean blank. Is there contamination problems in the LC and MS parts of the instrument associated with fatty acids? The fatty acid carryover peaks show up in any injection (blank) as well as no injection or 0 inj vol.

I am suggesting performing this analysis by GCMS, but need supporting info/theory/etc. Please help. :?