The transformer oil is absorbed in a few milliliters of pentane. The furan and furfurol derivatives are separated from the rest of the oil matrix by means of solid-phase extraction.
A few microliters of the extracted sample are placed on a chromatographic separation column using a mobile phase. Due to the polar interactions, the analytes remain on the stationary phase of the column with varying degrees of force. The sample is therefore divided into the individual analytes. The analytes gradually elute and are recorded by a UV/VIS detector after separation at a characteristic retention time. The following furan derivatives are detected in this process:
- 5-hydroxymethyl-2-furfurol (5HMF)
- 2-furfuryl alcohol (2FOL)
- 2-furfurol (2FAL)
- 2-acetylfuran (2ACF)
- 5-methyl-2-furfurol (5MEF)