Analysis of Stable Isotope Ratios of Triacetone Triperoxide

Triacetone triperoxide (TATP) explosive is frequently used by criminals because of its high power and easy preparation. Therefore, the traceability analysis of TATP is of great significance for fighting crime and maintaining public safety. The stable isotope ratio mass spectrometry (IRMS) is a high-precision tool for the measurement of stable isotope ratio, which has been widely used in food science, environmental protection, geology, forensic science, and other fields. A few of studies have been reported to apply IRMS to analyze the isotopic ratio of TATP, verifing the feasibility of using IRMS to distinguish TATP from different sources. However, to realize the precise source tracing of TATP, it is necessary to further study the influence of synthetic raw materials and processes on the stable isotope ratio of TATP. To the end, in this work IRMS was used to explore the characteristics of stable isotope ratio of TATP synthesized by different raw materials and processes. We revealed that the values of carbon isotope (δ¹³C), hydrogen isotope values (δ²H) and oxygen isotope values (δ¹⁸O) of TATP ranged from -31.62‰ to -27.50‰ (SD<0.06‰), from -144.09‰ to -107.85‰ (SD<2.78‰) and from 30.61‰ to 38.02‰ (SD<0.5‰), respectively. The variation in carbon and hydrogen isotope values mostly determined by the isotopic composition of the precursor acetone, which was the donor of the carbon atoms and the main donor of hydrogen atoms in TATP. The variation in oxygen isotope values mostly depended on the isotopic composition of the precursor hydrogen peroxide, which was the donor of oxygen atoms in TATP. Significantly, the reaction pathway of TATP synthesized from acetone and hydrogen peroxide was postulated based on the results of IRMS. Moreover, a linear relationship was found for the carbon isotope values of the precursor acetone and TATP. This can be used in forensic investigations to link TATP samples to their corresponding acetone precursors. The linear relationship of the hydrogen isotope values of the precursor acetone and TATP was poor because of the possible hydrogen exchange during the synthesis. Benzoic acid serving as a catalyst has no significant impact on the stable isotope ratios of TATP. However the reaction time has a great influence on the isotopic composition of TATP. With the increasing of reaction time, the reaction yields increased and the carbon isotope values of TATP also increased because of the kinetic isotope effect. These finding are of great significance for investigating the source of TATP at the crime scene.