Forensic analysis of acrylic fibers by pyrolysis-gas chromatography/mass spectrometry

Pyrolysis/gas chromatography/mass spectrometry is proposed as a suitable technique for the differentiation of colorless polyacrylonitrile-based fibers with similar morphology. Quite frequently, a comparison between items of this type is necessary to assess the reliability of the reconstruction of a crime. Hydrocyanic acid, acetonitrile, acrylonitrile, acetic acid, methacrylonitrile, 1,3-dicyanopropene, 1,3-dicyanobutene, 2,4-dicyanobutene and 1,3,5-tricyanohexane were the degradation products deemed most useful for discrimination of the samples. Principal component analysis was employed for pattern recognition. Although fibers are industrial products very similar in structure and properties, the concentration and the distribution of head-to-head arrangements of the monomers differ slightly. These structural defects alter in a significant way the composition of the mixture of the pyrolysis products. This allows for the differentiation of fibers, which are often important traces in criminal investigations.