Lipids – including saturated (SFA), monounsaturated (MUFA), and polyunsaturated fatty acids (PUFA) play a crucial role in maintaining homeostasis in farm animals and humans, as they are involved in numerous essential physiological processes. However, MUFA and PUFA, especially highly unsaturated fatty acids, like LPUFA (with more than three double bonds), are very sensitive to per-oxidation. Peroxidation of PUFA in lipids leads to the formation of aldehydes (e.g. 4-hydroxy-2-nonenal), dialdehydes (e.g. malondialdehyde (MDA)), formaldehyde (FA) or ketoaldehydes. MDA, the biomarker of lipid peroxidation, exhibit cytotoxic, mutagenic and carcinogenic properties. MDA can also inhibit enzymes associated with defending cells against oxidative stress. Similarly, FA, well known as an environmental pollutant, causes respiratory distress when inhaled at high concentrations, leading to lung damage. It has also been found to be mutagenic due to its high reactivity as a small molecule containing an electrophilic carbon. Thus, the main aim of our study was to develop novel pre-column procedures involving the derivatization of malondialdehyde (MDA), formaldehyde (FA) with 2,4-dinitro-phenylhydrazine (DNPH), and to optimise their analysis using C18-UFLC with photodiode detection (DAD). Both the original and simplified pre-column methods, especially when combined with C18-UFLC-DAD, are expected to enable selective and routine analysis of MDA and FA in plant oils and representative edible animal tissues (such as muscle, adipose tissue, liver, and brain). Plant oils (olive oil, rapeseed oil, wheat germ oil, marine algae oil): The pre-column method for determination of MDA, FA in plant oils as well as standard of MDA and FA involved only highly efficient derivatization with DNPH, followed by UFLC-DAD analysis. Briefly, the following reagents were added to ~50 mg of shaken plant oil in acidified methanol, BHT and DNPH solutions. The resulting mixture was shaken in the dark at room temperature for 1 hour. At the end of the derivatization, the mixture was centrifuged and the clear supernatant was then transferred to a vial. Then, 2-5 µL of the supernatant was injected onto the column for chromatographic analysis. The ovine tissues (muscles, adipose tissues, brain, and liver): To samples (~400 mg) of lamb tissues BHT in methanol and 4 mL of ethanol were added. After saponification, free MDA and FA were derivatized with DNPH at room temperature for 3 – 5 hours. Finally, before chromatographic analysis, the derivatized MDA and FA from the ovine tissues were dissolved in acetonitrile. The primary scientific novelty of our study is the use of new simple and effective pre-column methods combined with original binary elution and specific photodiode detection for the quantification of derivatized MDA and FA in selected plant oils and ovine tissues. In oils, direct derivatization with DNPH allowed quantification of MDA and FA without preliminary saponification of oils. On the other hand, in animal tissues, MDA and FA were debonded by gentle saponification and then free MDA and FA were derivatized with DNPH. The analytical column, elution program, and specific photodiode detection achieved satisfactory separation of MDA and FA from endogenous components in the final processed animal samples, when acetonitrile was added at a minimum volume ratio of 1:1 or higher. Indeed, the addition of acetonitrile reduces the solubility and a number of endogenous components in the analyzed samples. Our studies have shown that exposing plant oils or animal tissues to daylight and storing them for three weeks at room temperature leads to an increase in the concentrations of MDA and FA in the tested tissues. Compared to gas-chromatography (GC) with flame ionization detection (FID), our original fast-liquid chromatography with photodiode detection (LFLC-DAD) provided excellent separation of derivatized MDA and FA from the components of plant oils and edible parts of farm animals like muscles, adipose tissues, brain and liver. The proposed C18 liquid chromatography permitted satisfactory quantification of lipid peroxidation markers in food-related plant oils and farm animal tissues, offering the effective tool for studying oxidative stability and aldehyde accumulation in edible oils and animal products.