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Microspectrophotometric Analysis of Yellow Polyester Fiber Dye Loadings With Chemometric Techniques

NCJ Number
Forensic Chemistry Volume: 3 Dated: March 2017 Pages: 21-27
Date Published
March 2017
7 pages
In this study, background subtracted and normalized visible spectra from 10 yellow polyester exemplars dyed with different concentrations of the same dye ranging from 0.1 percent to 3.5 percent (w/w), were analyzed by agglomerative hierarchical clustering (AHC), principal component analysis (PCA), and discriminant analysis (DA).

Microspectrophotometry is a quick, accurate, and reproducible method to compare colored fibers for forensic purposes. Applying chemometric techniques to spectroscopic data can provide valuable information, especially when looking at a complex dataset. In the current project, systematic changes in the wavelength of maximum absorption, peak shape, and signal-to-background ratio were noted as dye loading increased. In general, classifying the samples into 10 groups (one for each exemplar) had poor accuracy (i.e., 51 percent); however, classification was more accurate (i.e., 96 percent) using three classes of fibers that were identified by AHC as having low (0.10-0.20 wt percent), medium (0.40-0.75 wt percent), and high (1.5-3.5 wt percent) dye loadings. An external validation with additional fibers and data generated by independent analysts confirmed these findings. Lastly, it was also possible to discriminate pairs of exemplars with small differences in dye loadings as a simulation of questioned (Q) versus known (K) comparisons. (publisher abstract modified)

Date Published: March 1, 2017