We report here the effectiveness of gas chromatography mass spectrometry techniques in establishing the ferrite-associated photocatalytic degradation mechanism of pesticide 2,4-dinitrophenol (2,6-DNP). Unlike the previously discussed DNP-degradation mechanisms that involve either oxidation or reduction reactions, ferrite-based ultraviolet (UV) photodegradation of DNP affords the nontoxic 6-hydroxy-3,5-dinitrohexa-2,4-dienal by an unusual water addition to the benzene core. We searched for and demonstrated the presence of an epoxide of DNP within the photodegradation process, which may unambiguously explain the novel photochemical mechanism. During the 15 min UV photoinduced process, DNP degradation efficiency on the zinc ferrite catalyst was calculated to be 82%, whereas the first-order kinetic rate constant k was as high as 3.4 x 10(-2)min(-1).