The spectra of the standards were measured using an
EcoAnalytix Biodiesel IR FAME Analyzer and a semidemountable
liquid cell with CaF2 windows and a 0.2 mm
pathlength. The spectra were ratioed against a background
of pure cyclohexane to approximately cancel absorbance
by the solvent. A more careful cancellation of the solvent
absorbance was deemed unnecessary because cyclohexane
is transparent in the carbonyl absorption region.