Principal Component Analysis and Analysis of Variance on the Effects of Entellan New on the Raman Spectra of Fibers

Abstract

During the forensic examination of textile fibers, fibers are usually mounted on glass slides for visual inspection and identification under the microscope. One method that has the capability to accurately identify single textile fibers without subsequent demounting is Raman microspectroscopy. The effect of the mountant Entellan New on the Raman spectra of fibers was investigated to determine if it is suitable for fiber analysis. Raman spectra of synthetic fibers mounted in three different ways were collected and subjected to multivariate analysis. Principal component analysis score plots revealed that while spectra from different fiber classes formed distinct groups, fibers of the same class formed a single group regardless of the mounting method. The spectra of bare fibers and those mounted in Entellan New were found to be statistically indistinguishable by analysis of variance calculations. These results demonstrate that fibers mounted in Entellan New may be identified directly by Raman microspectroscopy without further sample preparation.

The Analysis of Colored Acrylic, Cotton, and Wool Textile Fibers Using Micro‐Raman Spectroscopy. Part 2: Comparison with the Traditional Methods of Fiber Examination

“…As an overall result, based on the discriminating abilities of the different techniques utilized in this study and the collected sample set, the Raman method should be placed in the analytical sequence after microscopy and microspectrophotometry. From a practical perspective, it can be added that previous studies demonstrated that Raman analyses could be carried out directly through mounted microscopy preparations . Hence, this aspect offers the advantage to avoiding the removal of the fiber samples from their original preparations.…”

What can Raman spectroscopy do for criminalistics?

“…Any labels provided, such as sample concentration, type, or identity, is not considered by the model as it attempts to group spectra based on similarities. PCA has been used to discriminate between three different fiber types without interferences from a common mounting medium …”

“…As mentioned previously, the incorporation of chemometrics can be very useful for differentiation purposes. In one study, PCA was applied to Raman spectra to demonstrate that the presence of Entellan New (a common fixative for mounting fibers to glass slides) did not interfere with fiber analysis . It was shown that the three classes of fibers analyzed (i.e.…”

Collection management and study of microscope slides: Storage, profiling, deterioration, restoration procedures, and general recommendations

“…Non-destructive methods from materials sciences for the recognition of a mounting medium have not been applied to biological and geological slide preparations except in three cases (Garner & Horie 1984;Valentine-Baars & Kerbey 2014;Schmid et al 2016), but at least some Raman spectra of natural resins and of the mounting medium Entellan® new are Available from: art, archaeological, and forensic sciences (Edwards et al 1996;Daher et al 2010;Yu & Sandercock 2012). In a first step to overcome the disappointing situation for microscope slides, a database of Raman spectra of the known chemical components of mounting media and coverslip seals as well as spectra of freshly made media has been started by our team (Schmid et al 2016).…”