[en] The lifetime of the extraction system TBP Dodecane-aqueous HNO. In the Purex process is limited by radiolytic and hydrolytic decomposition of the extracting and diluting agent which is indicated by an increased retention of fission products, especially zirconium. In this work, the radiolytically formed complexing agents responsible for this are enriched (molecular distillation) and separated in several fractions by liquid chromatography. The chemical composition of these fractions was identified by a combination of gas chromatography and mass spectrometry, supplemented by infra-red spectroscopy. As for doubtful complexing agents, they are mainly long-chain phosphoric acid esters, and, to a lesser extent, the existence of polycarbonyl compounds is suspected. The high molecular weight components of the phosphate ester fraction could be separated by gas chromatography and identified as oligomeric phosphate esters. (author)