Desenvolvimento de métodos para análises de resíduos de incêndio utilizando extração por SPME e determinação por GC/MS e GCXGC/Q-TOFMS/MS

Abstract

Climate change is leading to an increase in fires in various parts of the world, including Brazil. As a result, the demand for fire debris analysis is expected to grow, with the aim of clarifying the origin and motivations, including arson, through the detection of burning accelerants. However, the residues of accelerants contained in fire debris can present challenges to their correct identification, caused mainly by acidification, microbiological degradation, weathering and matrix effect. Faced with this challenge, the aim of this work was to develop an innovative method, guided by the principles of green chemistry, DI-SPME-GCxGC/Q-TOFMS/MS for analyzing fire debris obtained under controlled burning with liquid accelerants. The development of the method included the optimization of chromatographic and extraction conditions. Optimization of orthogonality in GCxGC was achieved by liquid injection of burning accelerants, under analysis of the following factors: heating rate, carrier gas flow (helium), modulator temperature, modulation period, cold jet flow and hot jet time. From the Factorial Design, it was concluded that the statistically significant factors were: heating rate, modulation period and modulator temperature. The DI-SPME extraction conditions were also optimized using Factorial Design. The samples were produced by completely burning paper (5,0 cm x 5,0 cm) doped with a mixture of gasoline and diesel. Due to the need to increase the useful life of the fiber for SPME, a Teflon device was developed for the first time and used inside the vial during extraction. The following were statistically significant: extraction time (45 min) and desorption time (10 min), extraction temperature (80ºC) and desorption temperature (270ºC), as well as the modifier (ethyl acetate). Finally, the following figures of merit were evaluated: linear range, detection and quantification limits, precision and reproducibility for linear alkanes C14-C18, present in petroleum-based burning accelerants. The method showed low LODs, in the range 2.9 - 28.3 µg L-1, good repeatability, in the range 6.8% - 25.4% and intermediate precision in the range 12.0% - 20.8%. In addition, the method developed has the potential for automation and miniaturization.