How Useful is Pyrolysis‐GC/MS for the Assessment of Molecular Properties of Organic Matter in Archaeological Pottery Matrix? An Exploratory Case Study from North‐West Spain

Abstract

We applied pyrolysis-GC/MS to archaeological potsherds from prehistoric settlements in north-west Spain, some of which are conspicuously black or exhibit a black inner core from incomplete burn-out. Virtually all pyrolysis products could be related to thermally modified material (partially polycondensed aromatics and short-chain alkyl moieties) that most probably formed during firing (as opposed to cooking). Principal component analysis and supporting evidence (elemental composition, colour parameters and SEM microscopy) showed that the firing conditions (redox conditions and firing intensity) control pyrolysate composition. Laboratory experiments are required to fully understand the pyrolysis fingerprints and sample pre-treatment might enhance the information obtained.

Use of Thermally Assisted Hydrolysis and Methylation (THM-GC-MS) to Unravel Influence of Pottery Production and Post-Depositional Processes on the Molecular Composition of Organic Matter in Sherds from a Complex Coastal Settlement

“…Monocyclic aromatic products include penta-and hexamethylbenzene (14.5 ± 11.4%), which may originate from marine sources [38] and which had not been observed in a study of fragments from non-coastal settlements in NW Spain [20]. This may indicate that some of N-compounds also originate from marine sources such as plankton, as will be discussed later.…”

“…In addition to microbial N, these compounds (except for succinic acid ME) can also originate from plant protein, but as discussed below, on the basis of statistical data evaluation, this is an unlikely source of N. Finally, the N-compound benzonitrile was also identified in the chromatograms of most samples. The most probable source of benzonitrile is pyrogenic OM (PyOM) [20]. Many compounds with at least one atom of nitrogen (N-compounds) were identified (18.2 ± 11.2%; Appendix A), further indicating the contribution of microbial OM to the molecular fingerprints.…”

“…In addition to microbial N, these compounds (except for succinic acid ME) can also originate from plant protein, but as discussed below, on the basis of statistical data evaluation, this is an unlikely source of N. Finally, the N-compound benzonitrile was also identified in the chromatograms of most samples. The most probable source of benzonitrile is pyrogenic OM (PyOM) [20].…”

“…On the other hand, it has a strong capacity to provide a general screening of organic constituents that can be present, such as soot, charred temper, food residues and OM from the burial environment. Conventional analytical pyrolysis (Py-GC-MS) has been applied to archaeological potsherds with some frequency (e.g., [10,[20][21][22][23]). Kaal et al [20] performed statistical data evaluation of Py-GC-MS fingerprints of 24 ceramic samples from various settlements in NW Spain and compared the results with those from color and elemental analyses.…”

“…Conventional analytical pyrolysis (Py-GC-MS) has been applied to archaeological potsherds with some frequency (e.g., [10,[20][21][22][23]). Kaal et al [20] performed statistical data evaluation of Py-GC-MS fingerprints of 24 ceramic samples from various settlements in NW Spain and compared the results with those from color and elemental analyses. Another pyrolysis method is thermally assisted hydrolysis and methylation THM-GC-MS [24], in which a reagent such as tetramethylammonium hydroxide (TMAH) is added to protect polar functional groups against pyrolytic degradation and improve their chromatographic separation [24].…”