For the determination of malondialdehyde a derivatisation step, in which protein bound malondialdehyde is hydrolyzed and converted into a fluorescent probe (60 min at 95 °C) is performed. The fluorescent probe is then cooled (2-8°C), centrifuged, mixed with a reaction solution and injected into the HPLC system. The isocratic separation via HPLC at 30°C, using a ''reversed phase`` column, lasts 4 minutes for one sample. The chromatograms are recorded by a fluorescence detector. The quantification is performed with the delivered calibrator; the concentration is calculated via integration of the peak heights. Sample Types: serum, plasma. Time: 1 hour ? In a healthy body, oxidative and reductive processes are in a balance. Free radicals (reactive oxygen species) are eliminated by antioxidants. In case of a lack of antioxidants free radicals react with cell structures. A reaction of free radicals with unsaturated fatty acids leads to lipid peroxidation products. A reaction of free radicals with poly-unsaturated fatty acids generates malondialdehyde and/or 4-hydroxynonenal. These secondary lipid peroxidation products might react with other molecules in the cell. Modifications of the DNA-based adenine or guanine result in incorrect transcripts. A reaction of free radicals with proteins leads to an alteration or loss of function. The creation of neoAntigenss is possible. NeoAntigenss are recognized by the immune system, thus resulting in autoimmune diseases. The participation of lipid peroxidation products have been discussed in several diseases such as atherosclerosis, tumor genesis, rheumatism and reperfusion injury after transplantation.