As a novel chemical marker

methanol has been widely applied to evaluate the ageing state of insulating paper in recent years. Methanol gas sensor (MGS) could be applied to detect the methanol content in transformer oil for its high portability and stability. However

it has the defects of a high limit of detection (LOD) and poor anti-interference performance. Therefore

a novel method of detecting methanol in transformer oil based on MGS with the solid-phase extraction (SPE) technology was investigated in this paper. A detection platform for methanol in transformer oil based on SPE was established

and the SPE experimental process and the crucial parameters were optimised. The results show that the SPE decreased the LOD of MGS from 0.4 to 0.2 ppm and effectively eliminated the interfering substances in oil. Although a part of methanol would be lost during the SPE process

the regression correction coefficient was proposed to correct the evaluation errors. The results indicate that the average relative errors decreased from 17.09% to 4.38%

and the proposed method has good applicability.