Identification of small bits of natural leather by pyrolysis gas chromatography/mass spectrometry

The analysis of diketodipyrrole and 2,5-diketopiperazines, detected as pyrolysis products from collagen, which is a main component of natural leathers, by pyrolysis gas chromatography-mass spectrometry (Py-GCMS), was examined for the development of a forensic identification method of small bits of the natural leathers used in this study. Natural leather samples (very small pieces) from the five kinds of animals, such as cow, pig, sheep, kangaroo, and ostrich, collagen from calf-skin, collagen powder from pig-skin, wool fibers, and silk fibers were used as samples. The results of Py-GCMS analysis showed that natural leather samples from five kinds of animals were composed of collagen, which was distinguished from the other protein fibers, such as a wool fiber and a silk fiber. The discrimination of the leather samples from five kinds of animals was difficult. However, if a leather samples with a weight of more than approximately 25 mu g existed as a sample, the Py-GCMS analysis examined in this study could detect a diketodipyrrole and 2,5-diketopiperazines corresponding to dipeptides, which were composed of major amino acids, such as glycine (Gly), proline (Pro), alanine (Ala), and hydroxyproline (Hyp) from collagen. Accordingly, the analytical method by Py-GCMS shown in this study can be newly applied to the forensic identification of small samples of natural leathers.