GC MS ANALYSIS OF CARBOXYLIC-ACIDS IN PETROLEUM AFTER ESTERIFICATION WITH FLUOROALCOHOLS

The GC-MS characteristics of carboxylic acid esters prepared from fluo rine-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-1-butyl (HFB) esters was approximately equiva lent to that of methyl esters. Mass spectra of TFE and HFB aliphatic e sters 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 po tential interfering ions. Data for about 70 individual TFE and HFB est ers are reported. Application of the methodology to a petroleum-derive d carboxylic acid concentrate resulted in identification of straight c hain, isoprenoid, methyl-substituted straight chain (2-, 3-, 5-,10-, 1 2-positions along chain), and dimethyl-substituted straight chain acid s containing from 11 to 22 carbons. Benzoic acid and homologs with up to 3-carbons in alkyl substitutents were minor components in the sampl e. The procedure provided for forming TFE and HFB esters from free aci ds requires less time and effort than a previously reported method, wh ile retaining its capability for achieving essentially quantitative co nversion. Free hydroxyl groups in alcohols and phenols are converted t o trifluoroacetate esters concurrently with formation of TFE/HFB carbo xylic acid esters. The reaction products, including compounds with two functional groups (diacids, salicylic acid, etc.), chromatograph well on conventional nonpolar GC stationary phases.