To Je***: Based on the searching on my NIST/EPA/NIH 2005 Mass Library, I got some crabs :>) Peak @ 21.36 min -> 2,6-di-tert-butyl-4-sec-butylphenol
So please DO NOT trust this Mass Library Searching. will update when I find something new.
Update@Aug-12-2008
Maybe PDMS works. Also it maybe work on the acids, alcohol, aldehydes (ketone). However, that is not a good one. -> “the Supelco 57301 the fiber ( 100 um) PDMS” has better SPE affinity to the high molecular weight non-polar compounds, that maybe the reason you got so many unknown peak ( high molecular compounds).
So if your analyte is low molecular polar acid, alcohol, aldehydes (ketone), recommend the SPME fiber assembly, Carbpwax-Polyethyele (PEG), Supelco#57355-U, it should be good to go for the polar low molecular compounds.