Previous analyses of organic peroxide explosives have focussed on identification of the explosive itself, and were performed using explosive samples synthesized from laboratory-grade precursors. In this work, analytical studies of precursors obtained from retail outlets identified compounds that could be carried over into the explosives as impurities during synthesis. Forensic and intelligence information may be gained by the identification of possible precursor impurities in explosive samples. This hypothesis was tested using triacetone triperoxide and hexamethylene triperoxide diamine prepared from domestically available off-the-shelf precursors. Gas chromatography–mass spectrometry analysis showed that compounds originating from such precursors could be detected in the organic peroxide samples at different stages in their purification. Furthermore, some compounds could also be detected in the residues of samples that had been subjected to thermal initiation.