Rapid direct analysis of p-xylene oxidation products by reversed phase high-performance liquid chromatography

A reversed-phase high-performance liquid chromatographic (HPLC) method is developed for the determination of the products of liquid phase oxidation of p-xylene to terephthalic acid catalyzed by cobalt naphtenate with methyl benzoate as a solvent. Analyses are performed on a 250- × 4.6-mm octadecylsilica (ODS; C18) bonded phase column with a 10- × 3-mm guard column in 22 min. A three-component mobile phase (methanol, acetonitrile, water) is used for gradient elution, and ultraviolet detection is selectively performed at 220 and 254 nm. The internal standard method (using cumene as the internal standard) is employed. The developed method avoids filtration, extraction, and derivatization pretreatment of the samples.