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Watson, P, Assi, S and Ralebitso Senior, TK (2022) Evaluating attenuated total reflectance infrared and near infrared spectroscopy for classifying M. musculus grave soil in the presence of clothing material. In: Joint Pharmaceutical Analysis Group Symposium, London, UK.
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Abstract
Objectives: Common methods utilised for establishing the time elapsed for unattended death scenes rely on physical atrophy. Predicting postmortem interval (PMI) relies on visual inspection, total body scoring and rigor mortis where the three are influenced by biotic and/or abiotic variables. These variables include the presence of different types of textiles that affect the cadaver decomposition island (CDI) in the type of fluids and decomposition products in the surrounding environment.
Therefore, this work explores the impact of clothing material on the formation and timeline of CDI in simulated grave soil using attenuated total reflectance Fourier transform infrared (ATR-FTIR) and near infrared (NIR) spectroscopy.
Materials and Methods: Grave soil evaluated in this study included samples that had carrions under different conditions including: (1) unwrapped carrions, (2) wrapped carrions with three types of fabric being cotton, polyester and viscose. Samples were stored in boxes and monitored over 170 days for environmental factors (temperature, pH, humidity) and for physicochemical properties. Physicochemical properties were determined using ATR-FTIR and NIR spectroscopy. Wrapped and unwrapped soil samples were measured frequently at weekly intervals through glass vials for NIR spectra or by placing 1-2 mg of soil on the diamond accessory for ATR-FTIR spectra. In both cases, spectra were exported into Matlab 2019a where spectral interpretation and analysis were applied. Spectral interpretation comprised comparing the absorbances obtained for soil samples against the reported literature. Spectral analysis involved applying principal component analysis (PCA) that informed about patterns in the absorbances of soils both unwrapped and wrapped with different fabrics.
Results: Both ATR-FTIR and NIR spectra informed about the chemical and physical profile of soil samples with unwrapped and wrapped cadavers.
ATR-FTIR spectra highlighted shifts in both O-H stretching and bending bands at ~3300 cm-1 and ~1640 cm-1, respectively. Grave soil associated with M. musculus exhibited increased intensity at ~1250 cm-1 C-O-C ester stretching, indicative of volatile organic compounds that produce the characteristic smell of death. This peak was delayed significantly in response to wrapping in various textiles. Although bands relating to lipid (~1760 cm-1) and protein (1690/1680 cm-1) degradation were identified on ATR spectra from the textiles post-exhumation, these were not identified in the respective soil samples. Both symmetrical and asymmetrical CH2 wagging present at 2920 cm-1 and 2850 cm-1, suggested the presence of saturated and unsaturated fatty acids.
NIR spectra also highlighted temporal changes in -OH bonds (1420 nm). Although not highlighted by ATR, amides and amine secondary and tertiary overtone profiles, were detectable in soil samples associated with decomposing M. musculus between 1000 and 1200 nm.
When PCA was applied to both types of spectra, it showed its ability to distinguish between the different types of fabric that the cadavers had been wrapped with.
Conclusions: Our findings showed that ATR-FTIR and NIR spectroscopy offered a non-destructive approach to understand the decomposition of cadaver remains in soil. Moreover, both techniques informed about the impact about different textiles on the formation of CDI. In this respect, the presence of textiles has delayed CDI formation. By combining both techniques with PCA, soil samples could be classified indicating to the type of fabric the cadaver had been wrapped with.
| Item Type: | Conference or Workshop Item (Poster) |
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| Subjects: | R Medicine > RM Therapeutics. Pharmacology |
| Divisions: | Pharmacy & Biomolecular Sciences |
| Related URLs: | |
| SWORD Depositor: | A Symplectic |
| Date Deposited: | 23 Jan 2023 14:16 |
| Last Modified: | 23 Jan 2023 14:16 |
| URI: | https://researchonline.ljmu.ac.uk/id/eprint/18683 |
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