The radiation-chemical transformations of Purex solvent, 30% TBP-n-dodecane-HNO3, arising from radiolysis of nitric acid were examined by gas chromatographic fingerprinting of the radiolyzed system. The present study describes a procedure for identifying diluent degradation products by gas chromatographic, infrared and gas chromatographic-mass spectrographic assay. The identified gas chromatographic signatures can be used to monitor the growth of diluent degradation products (DDP) like nitroparaffins, long chain alcohols, and paraffins in the Purex solvent before its recycling. The increase in the concentration profiles of these species with absorbed dose parallels the increase in the retention of Ru, Zr, and Pu by the diluent phases resolved (by the phosphoric acid equilibration method) from the radiolyzed solvent under recycling conditions.