Nondestructive Total Excitation-Emission Fluorescence Microscopy Combined with Multi-Way Chemometric Analysis for Visually Indistinguishable Single Fiber Discrimination

MUÑOZ DE LA PEÑA, A; MUJUMDAR N; HEIDER E; GOICOECHEA H C; MUÑOZ DE LA PEÑA, D; CAMPIGLIA, A D

ANALYTICAL CHEMISTRY

AMER CHEMICAL SOC

Lugar: Washington; Año: 2016 vol. 88 p. 2967 - 2975

0003-2700

The potential of total excitation-emission fluorescence microscopy combined with multi-way chemometric analysis was investigated for the forensic analysis of textile fibers, emulating the case in which a fiber encountered in a crime scene is compared with the fibers of a textile of the same color belonging to a suspect. For that, four pairs of visually indistinguishable fibers from four different textiles were selected. The fibers consisted of nylon 361 dyed with acid yellow 17 and acid yellow 23, acetate satin 105B dyed with disperse blue 3 and disperse blue 14, polyester 777 dyed with disperse red 1 and disperse red 19, and acrylic 864 dyed with basic green 1 and basic green 4, and were investigated using a non-destructive approach, which is of paramount importance to preserve the physical integrity for the fibers for further court examination. Excitation emission matrices were recorded with the aid of an inverted microscope coupled via a bifurcated fiber-optic probe to a commercial spectrofluorimeter. The full information content of excitation-emission matrices was processed with the aid of principal component analysis (PCA), unsupervised parallel factor analysis (PARAFAC), PARAFAC supervised by linear discriminant analysis (LDA), and discriminant unfolded partial least squares (DU-PLS). The ability of the latter algorithm to classify the four pairs of fibers, and distinguish the questioned fiber and the known fiber to exclude the possibility that both could have originated from a common source, demonstrates the advantage of using the multidimensionality of fluorescence data formats for the non-destructive analysis of forensic fiber evidence.