Gas chromatographic analysis of aromatic carboxylic acids in the presence of C1?C22 fatty acids and C2?C16 dicarboxylic acids esterified in aqueous solutions as the n-propyl esters

Summary The direct esterification and gas chromatographic analysis of aromatic carboxylic acids as n-propyl esters is described.Derivatization is performed in aqueous solution with n-propanol in the presence of sulfuric acid. The n-propyl esters of benzoic, phthalic, trimellitic and pyromellitic acids permit their gas chromatographic separation from each other and from fatty acids and aliphatic dicarboxylic acids. At mode ratios of H₂O]/n-PrOH]0.03 the water present does not interfere with the esterification reaction. At mole ratios above 0.03 anhydrous sodium sulfate is used for binding the water, at mole ratios of Na₂SO₄anh.]/H₂O]=0.51–1.52 and of H₂SO₄]/Na₂SO₄anh.]=0.43–1.28, respectively.