A cytotoxic aldehyde, 4-hydroxy-2E-nonenal (4-HNE), is formed by lipid peroxidation in cells. In order to investigate formation of 4-HNE and the related aldehyde, 4-hydroxy-2E-hexenal (4-HHE) in cooking oil, we developed a quantitative analytical method for the aldehydes using synthesized deuterium labeled aldehydes as the internal standards. The cooking oil including internal standards was clean-upped by a cartridge-type silica-gel column, and the hydroxyl groups of 4-HNE and 4-HHE were derivatized to trimethylsilyl ether for the GC/MS measurement. Commercial cooking oils were heated and analyzed using the developed isotope-dilution method. 4-HNE levels increased according to heating time, and the final concentrations differed about five times among analyzed cooking oils. In the oil repeatedly used by tempura cooking, 4-HNE increased following the rise of peroxide value (POV) in the first several use, and then its concentration reached a plateau.A cytotoxic aldehyde, 4-hydroxy-2E-nonenal (4-HNE), is formed by lipid peroxidation in cells. In order to investigate formation of 4-HNE and the related aldehyde, 4-hydroxy-2E-hexenal (4-HHE) in cooking oil, we developed a quantitative analytical method for the aldehydes using synthesized deuterium labeled aldehydes as the internal standards. The cooking oil including internal standards was clean-upped by a cartridge-type silica-gel column, and the hydroxyl groups of 4-HNE and 4-HHE were derivatized to trimethylsilyl ether for the GC/MS measurement. Commercial cooking oils were heated and analyzed using the developed isotope-dilution method. 4-HNE levels increased according to heating time, and the final concentrations differed about five times among analyzed cooking oils. In the oil repeatedly used by tempura cooking, 4-HNE increased following the rise of peroxide value (POV) in the first several use, and then its concentration reached a plateau
