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.
- Esterification in aqueous solution
- Gas chromatography
- n-Propyl esters of aromatic polycarboxylic acids
ASJC Scopus subject areas
- Analytical Chemistry
- Clinical Biochemistry
- Organic Chemistry