Stop-FlowGCof anEssential Oil Standard
Essential oil samples are complexmixtures of organic compounds. Awide
rangeof concentrations andboilingpoints typically are represented. The
FragranceMaterial Association (FMA) has proposeda testmix representativeof
the variety of compounds found inessential oil samples (seeTable III). Thismix
was used to test theapplicability of the stop-flow technique to this typeof
sample.
InFigure8, thedual columnanalysis of theFMA testmix is shown, withno
stop-flowpulses applied. The first column contains apolar polyethyleneglycol
stationary phase; the second column contains anon-polar 100%
dimethylpolysiloxane stationary phase. GC conditions havebeenoptimized to
reduce the run time toapproximately 10minutes. At theendof the first column,
thymol and cinnamyl acetate coelute; these compounds resolveat theendof
the second column. Limoneneandeucalyptol areadequately resolvedon the
first column; however, these compounds arenot well resolvedat theendof the
second column. A6 second stop-flowpulseat 187 seconds gives significantly
better resolutionof limoneneandeucalyptol, as shown inFigure9. InFigure
10, theeffect of the lengthof the stop-flowpulse is shown.
