Detection Limits for Blood on Fabrics Using Attenuated Total Reflection Fourier Transform Infrared (ATR FT-IR) Spectroscopy and Derivative Processing

• NCJ Number: 252316
• Date Published: January 2017
• Author(s): Zhenyu Lu, Stephanie A. DeJong, Brianna M. Cassidy, Raymond G. Belliveau, Michael L. Myrick, Stephen L. Myrick
• Award: Multimode Imaging in the Thermal Infrared: Validation for Blood, Extension to Latent Prints

Annotation

This project used attenuated total reflection Fourier transform infrared spectroscopy (ATR FT-IR) to detect blood stains based on signature protein absorption in the mid-IR region, where intensity changes in the spectrum can be related to blood concentration.

Abstract

Partial least squares regression (PLSR) was applied for multivariate calibrations of IR spectra of blood dilutions on four types of fabric (acrylic, nylon, polyester, and cotton). Gap derivatives (GDs) were applied as a preprocessing technique to optimize the performance of calibration models. This project reports a much-improved IR detection limit (DL) for blood on cotton (2700× in dilution factor units) and the first IR DL reported for blood on nylon (250×). Due to sample heterogeneity caused by fabric hydrophobicity, acrylic fabric produced variable ATR FT-IR spectra that caused poor DLs in concentration units compared to previous work. Polyester showed a similar problem at low blood concentrations that lead to a relatively poor DL as well; however, the increased surface sensitivity and decreased penetration depth of ATR FT-IR make it an excellent choice for detection of small quantities of blood on the front surface of all fabrics tested (0.0010 µg for cotton, 0.0077 µg for nylon, 0.011 µg for acrylic, and 0.0066 µg for polyester). (Publisher abstract modified)