Quantitative and qualitative analysis of chitin in fossil arthropods using a combination of colorimetric assay and pyrolysis–gas chromatography–mass spectrometry

Abstract

A colorimetric assay and pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS) were used to study chitin in a variety of fresh, laboratory decayed and fossil arthropod cuticles, the last ranging in age from Upper Cretaceous (approximately 65 Ma) to Holocene. The results of the colorimetric assay of chitin in fresh arthropod cuticle are consistent with values reported in the literature. Py–GC–MS, although non-quantitative, yields pyrolysis products characteristic of chitin and other constituents of the cuticle. Both the colorimetric and Py–GC–MS methods demonstrate that chitin is preserved in Quaternary and some Tertiary specimens. In some fossil cuticles the colorimetric assay gave a positive response even though pyrolysis products characteristic of chitin were not detected. Py–GC–MS revealed the presence of non-chitinous carbohydrates in these cuticles, which presumably accounts for the positive result obtained from the colorimetric assay. The results show that analytical methods are required to provide reliable quantitative and qualitative information on chitin in fossil specimens. This investigation establishes the utility of this approach to the study of chitin in the geosphere, and where chitinous material has been degraded or chemically modified in modern environments.