A gas chromatography-liquid chromatography combined analysis method is developed to address the complexity and analytical challenges in the oxidation process of 1,2,4-trimethylbenzene.A Shimadzu GC-2014C gas chromatographic instrument equipped with an SE-54 column(0.32 mm × 30 m,a film thickness of 0.25 μm)and a hydrogen flame ionization detector are used to quantitatively detect the low-boiling point products such as 1,2,4-trimethylbenzene,alcohols,aldehydes,and carboxylic acid derivatives.An Agilent-1200 liquid chromatography system with a C18 column(5 mm×250 mm,a particle size of 5 µm),and a binary mobile phase of methanol-water are employed to detect the high-boiling point products,including 1,2,4,5-benzenetetracarboxylic acid,1,2,4-trimellitic acid,and terephthalic acid.Relative molar correction factors are obtained through using the standard curve method.4-Methylphthalic acid,which exports peaks at both gas and liquid chromatography,is served as a bridging substance to correlate the two analysis methods for quantitative analysis of the products.Accuracy experiments demonstrate that the analysis errors are all below 1.0％.
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