GC MS ANALYSIS OF PHENOLIC-COMPOUNDS IN FUELS AFTER CONVERSION TO TRIFLUOROACETATE ESTERS

The GC-MS characteristics of trifluoroacetate esters of phenolic compo unds are discussed. Linear temperature programmed retention indices an d total ion current MS response factors of over 120 phenolic esters ar e reported. The main GC advantages from analysis of trifluoroacetate e sters as compared to plain phenols are enhanced volatility and improve d resolution. For example, the elution temperature of a given phenol i s typically 50-degrees-C greater than that of the corresponding triflu oroacetate ester. Also, while retention of compounds with two trifluor oacetate groups is only moderately greater than monoesters, underivati zed dihydroxy compounds are very difficult to elute from any GC column . Complete resolution of isomeric C0-, C1- and C2-alkylphenol esters i s readily achieved on conventional fused silica GC columns; resolution of the corresponding underivatized compounds requires specialized GC columns with low temperature limits. In general, mass spectra of trifl uoroacetate esters are more characteristic of a given structure than t hose of the corresponding phenols and may be more rigorously interpret ed towards structural elucidation. A table in the report summarizes so me of the more important spectral features used in compound identifica tion. Example applications in analysis of coal-, shale- and petroleum- derived materials are presented. Selected ion monitoring is used to de termine individual phenolic components in whole distillates; reconstru cted ion chromatograms are used to illustrate distributions of selecte d species as a function of fuel storage and thermal stress.