ω-oxo-fatty acids, also known as aldehydic fatty acids, are major products of fatty acid oxidation and pose potential health risks. When bound to glycerol, ω-oxo-fatty acids (core aldehydes) can be ingested with food. Challenges in GC-MS quantification include the absence of an appropriate internal standard. Additionally, substantial analyte losses during sample preparation, caused by the high volatility of short-chain compounds, alter their pattern based on molecular weight. In this study, among various tested derivatization methods, the formation of ω-dioxane derivatives demonstrated improved recovery rates after three evaporation cycles. For methyl 7-oxo-heptanoate, recovery increased from 43 % to 88 %, while recovery rates for different chain lengths and a novel synthesized internal standard improved from a range of 43 %-76 % to 87 %-92 %. Additionally, ω-dioxane derivatives displayed favorable GC-MS behavior, enabling clear identification and increased sensitivity. Finally, ω-oxo-fatty acids were quantified as their ω-dioxane-derivatives in thermally treated sunflower and rapeseed oil.