Forensic analysis of textile fibers exposed to cigarete smoke using non-destructive RT-EEM microscopy

HUG HAYES; A CAMPIGLIA,; MUÑOZ DE LA PEÑA, A; GOICOECHEA, H C

Atlanta

Congreso; PITTCON 2016; 2016

Textile fibers are common pieces of evidence found at crime scenes. The analysis of these fibers can provide pivotal forensic information regarding solving casework. Current research has employed non-destructive methodologies to analyze the components that are dyed onto various types of textiles. Some of these methods utilize optical spectroscopy which examines the effect on the fibers in the presence of visible and ultraviolet light. Research in our group has focused on the fluorescence characteristics of textile fibers [1, 2], which can undergo multiple chemical and physical alterations due to various environmental conditions. These conditions can ultimately change the fluorescent spectral features of the individual fibers and provide useful information on the history of the fiber. Herein, we present an investigation of the fluorescence properties of textile fibers exposed to a commercial brand of filtered cigarette smoke. The investigated cloths were acrylic, cotton, nylon, and polyester fabrics pre-dyed with basic green 4 (BG4), direct blue 1 (DB1), acid yellow 17 (AY17), and disperse red 4 (DR4) dyes, respectively. Room temperature excitation-emission matrices (EEMs) of cloths and single fibers were collected in the visible and ultraviolet regions of the spectrum with the aid of an inverted microscope fiber-optic coupled to a commercial spectrofluorimeter. The EEM data formats were analyzed using parallel factor analysis (PARAFAC), a well-known chemometric technique often utilized in unsupervised and supervised - linear discriminant analysis (LDA) - classification studies, as well as discriminant unfolded-partial least squares (DU-PLS). By decomposing the EEMs into the spectral profiles of individual fluorescence components, these second-order algorithms were able to differentiate unexposed fibers from exposed fibers. These results show promise for the discrimination of visually indistinguishable fibers on the bases of fiber history. [1] Single Fiber Identification with Nondestructive Excitation-Emission Spectral Cluster Analysis; K. Appalaneni, E. C. Heider, A. F. T. More, A. D. Campiglia*; Analytical Chemistry, 2014, 86, 6774-6780.[2] Enhancing Textile Fiber Identification with Detergent Fluorescence; N. Mujumdar, E. C. Heider, A. D. Campiglia*; Applied Spectroscopy, 2015, in press.Acknowledgements: This research was sponsored by the US National Institute of Justice (Grant #2011-DN-BX-K553) and MEyC of Spain (Project CTQ2014-52309-P and Award PRX14/00342).