Investigation of Raman Spectrometry in Molecules Associated with Human Decomposition
The determination of the time since death occurred, or post-mortem interval (PMI), is an important step in death investigations. Currently, the most common approach for determining PMI has been the application of different types of mass spectrometry. Mass spectrometry requires the sample to be dissolved or derivatized, resulting in sample destruction. Raman spectroscopy is a non-destructive technique that is capable of measuring analytes in samples that are in solid, liquid, or gas phases, making it particularly useful in forensic investigations. For this project, three molecules associated with human decomposition and PMI, hypoxanthine, indole, and 3-methylindole, were measured with both normal Raman and surface-enhanced Raman spectroscopy (SERS) with gold nanoparticles (AuNPs). Normal Raman was performed for the detection of solid analytes in soil. SERS was performed for the detection of dissolved samples in agarose, layered with soil. All analytes were detected in solid-state mixed with soil as well as in the compounds incubated in agarose and layered in soil. SERS will also be carried out in the blood of pigs, an animal more closely related to humans than other animal models. Determination of the concentrations of these analytes in bodily systems of animals will help to establish the means for a limit of detection study (LOD) and narrow down which research animals have the analytes present in their systems for longer-term decomposition studies.