The instrumental evaluation of blood decomposition volatiles on various substrates and their relationship to presumptive test methods

Date

2019-05

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Abstract

There is a research gap in the evaluation of blood decomposition processes and the use of potential blood decomposition odor markers in establishing time of death ranges. On-set of coagulation in terms of blood decomposition can potentially display vital signs in determining how long the blood has been drying. Research exploiting the use of canines for cadaver detection has associated challenges in regard to the age of the blood used as a training aid, and ultimately a lack of scientific foundation as to blood odor signatures with respect to decomposition time. This novel research is an evaluation of specific volatile organic compounds (VOCs) within three substrates at various stages of decomposition. This study simultaneously evaluated blood decomposition profiles on two target substrates and its effect on Bluestar’s intensity. The purpose of this research further intends to increase the knowledge of detection windows of the presumptive reagent, Bluestar, by introducing a parallel understanding of distinctive volatile odor profiles in relation to the number of resulting false negatives and the observable intensity based on apparent luminescence. This study analyzed blood at three distinctive time frames: fresh (0-72 hours), intermediate (96-144 hours), and late (168-216 hours) potentially revealing different VOCs specific to each phase. Instrumental evaluation utilized DVB/CAR/ PDMS coated SPME fibers that were injected into a GC-MS for the identification of extracted blood decomposition odor profiles at each of the three decomposition time frames. Within the three-phases, two substrates were analyzed: metal nails (zinc and stainless steel), to determine if the number of detected VOCs present in natural blood decomposition is affected by the substrate’s composition. The odor profile resulted in a total of twelve detected VOCs detected above the headspace of the human donated pathogen free blood. These compounds were detected with the blood-contaminated nails in lower abundance, thereby showing the effect of substrate interactions. As for the compounds detected in metal nails a total of three compounds were unique to the stainless steel and four compounds were found above the headspace of the yellow zinc nail substrate. This is also one of the first studies to evaluate commonly used chemical reagents such as Bluestar and correlate the field response with the specific odor signature for that blood sample time frame. Based on the scale ranking results, Bluestar’s luminescence did not highlight a correlation between intensity and aging of blood on the substrates. This research presents a bridge to the knowledge gap of blood odor profile composition and presumptive reagents.

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Keywords

Human blood, Volatile organic compounds (VOCs), Bluestar, SPME-GC/MS, Presumptive methods, Decomposition

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