SummaryThe GC-MS characteristics of carboxylic acid esters prepared from fluorine-containing alcohols were compared to those of methyl esters. The GC retention of 2,2,2-trifluoroethyl (TFE) esters was less than, and 2,2,3,3,4,4,4-heptafluoro-l-butyl (HFB) esters was approximately equivalent to that of methyl esters. Mass spectra of TFE and HFB aliphatic esters show significantly more intense molecular and key fragment ions than those of methyl esters. Also, owing to their significantly higher molecular weights, TFE or HFB ester molecular ions and most fragment ions of interest occur at significantly higher m/z values than most potential interfering ions.Data for about 70 individual TFE and HFB esters are reported. Application of the methodology to a petroleum-derived carboxylic acid concentrate resulted in identification of straight chain, isoprenoid, methyl-substituted straight chain (2-, 3-, 5-,lo-, 12-positions along chain), and dimethyl-substituted straight chain acids containing from 11 to 22 carbons. Benzoic acid and homologs with up to 3-carbons in alkyl substitutents were minor components in the sample.The procedure provided for forming TFE and HFB esters from free acids requires less time and effort than a previously reported method, while retaining its capability for achieving essentially quantitative conversion. Free hydroxyl groups in alcohols and phenols are converted to trifluoroacetate esters concurrently with formation of TFHHFB carboxylic acid esters. The reaction products, including compounds with two functional groups (diacids, salicylic acid, etc.), chromatograph well on conventional nonpolar GC stationary phases.

The GC-MS characteristics of trifluoroacetate esters of phenolic compounds are discussed. Linear temperature programmed retention indices and total ion current MS response factors of over 120 phenolic esters are reported.The main GC advantages from analysis of trifluoroacetate esters as compared to plain phenols are enhanced volatility and improved resolution. For example, the elution temperature of a given phenol is typically 50 "C greater than that of the corresponding trifluoroacetate ester. Also, while retention of compounds with two trifluoroacetate groups is only moderately greater than mono esters, underivatized dihydroxy compounds are very difficult to elute from any GC column. Complete resolution of isomeric Co-, Ci-and Cn-alkylphenol esters is 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 trifluoroacetate esters are more characteristic of a given structure than those of the corresponding phenols and may be more rigorously interpreted towards structural elucidation. A table in the report summarizes some of the more important spectral features used in compound identification.Example applications in analysis of coal-, shale-and petroleum-derived materials are presented. Selected ion monitoring is used to determine individual phenolic components in whole distillates; reconstructed ion chromatograms are used to illustrate distributions of selected species as a function of fuel storage and thermal stress.

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An analytical method which distinguishes between primary, secondary and tertiary amines has been developed. Trifluoroacetic anhydride, with 4-pyrrolidinopyridine as a catalyst, is used to form di-and mono-trifluoroacylated derivatives of primary and secondary aromatic amines, respectively. Tertiary aromatic amines such as quinoline do not react. GC/MS is then used to analyze the derivatized sample,,:. Retention indices and response factors (relative to 4-fluoroaniline) • are reported for >50 pure com?ounds known or expected to be present in fossil fuel base fractions. Also, results from the analysl s of base fractions from mildly hydrotreated SRC II coal liquids and petroleum-derived light cycle oils will be reported.