Determination of paper degradation by-products by direct injection on an HPLC column

The by-products of the thermal degradation of insulating paper include 2-furfural, 2-acetylfuran and 5-methyl-2-furfural. These furanic compounds are usually isolated by subjecting the insulating oil to a pretreatment stage on a silica solid-phase cartridge, or liquid-liquid extraction (IEC 1198) before analyzing them by high-performance liquid chromatography (HPLC). However, these procedures are time-consuming and not very practical. This paper describes an alternative analytical method, also based on HPLC, but not requiring pretreatment. The insulating oil is injected directly on a PRP-1 column. The furanic by-products are eluted in less than 20 min when a mixture of water and acetonitrile (75:25, v/v) is used as the mobile phase with a flow rate of 0.5 cm³/min. The by-products are detected by ultraviolet. In-service transformer oils have been analyzed by the new method and the results compared to those obtained using the IEC method as well as others obtained by a private laboratory. The paper stresses the simplicity and, in particular, the increase in productivity offered by the proposed method