Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) detection limits for blood on fabric: Orientation and coating uniformity effects |
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Affiliation: | 1. Chemistry Department, Francis Marion University, 4822 E. Palmetto Street, Florence, SC 29506, USA;2. Chemistry Department, Christian Brothers University, 650 E. Parkway South, Memphis, TN 38104, USA;3. Halliburton Energy Services, 3000 N Sam Houston Pkwy E, Houston, TX 77032, USA;4. Datamage Consulting LLC;5. Department of Chemistry and Biochemistry, The University of South Carolina, 631 Sumter Street, Columbia, SC 29208, USA |
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Abstract: | Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was used to analyze four types of forensically relevant fabrics coated with varying dilutions of blood. The blood was applied in two manners, dip coating with a smooth and uniform layer and drip coating with droplets from pipettes. Spectra of neat and dip coated fabrics were acquired using controlled orientations, and these were compared to spectra collected on samples with random orientations. The improved reproducibility seen in visual inspection of the spectra is confirmed by principal component and linear discriminant projections of the spectra, as well as by statistical hypothesis testing. Principal component regression (PCR), using the regions of the IR spectra associated with the amide A/B, I, II, and III vibrational bands (3500–2800, 1650, 1540, and 1350 cm−1), was employed on the more uniform dip coated spectra to estimate limits of detection for blood on two of the four fabrics – acrylic and nylon. These results demonstrate that detection limits for blood on fabrics can be decreased significantly by controlling for the orientation and face of the fabric samples while collecting spectra. Limits of detection for acrylic and nylon were found to be 196 × and 227 × diluted blood, respectively. |
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Keywords: | Detection limits DRIFTS Diffuse reflectance Blood on fabrics Forensics Multivariate analysis Principal component analysis Linear discriminant analysis Orientation effects Coating effects Infrared spectroscopy |
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