Methods

Analysis of archaeological material presents a number of challenges, including the small amount of sample available, the presence of complex molecular mixtures from more than one source, chemical alteration due to processing or degradation, and contamination. Furthermore, every sample is unique. These factors mitigate against simple interpretations of analytical results.

Recent developments in instrumental chromato-graphic techniques have enabled trace amounts of organic residues to be detected. Hence it is possible to analyse molecules surviving in an inorganic matrix such as pottery or soil, or surviving in morphological organic remains such as lipids in seeds or bone. Insoluble or polymeric fractions of residues that are not themselves volatile enough for conventional analysis can be broken up by pyrolysis, thereby allowing separation and identification of the fragments. Pyrolysis-GC-MS has been successfully applied to the recognition of biopolymers in fossil and recent higher plant resins, and to macromolecular debris remaining from the burning of food in archaeological pottery vessels.

Preparation of ancient lipids and natural products normally involves solvent washing of samples. Pre-fractionation of the lipid residue can be undertaken using microscale column chromatography or TLC. Prior to analysis, unhindered acid functionalities are derivatized by treatment with diazomethane. Trimethylsilylation using N,0-fo/s(trimethylsilyl) triflouroacetamide (BSTFA) + 1% trimethylchloro-silane (TMCS) is used for the derivatization of hindered carboxyl groups and alcohols. In some cases an internal standard is added to the sample to quantify yield.

GC remains a useful screening technique prior to GC-MS and can provide fingerprint chromatograms, whereby a complex set of peaks in a mixture can be matched to those in reference samples. Nevertheless, since molecular alteration is likely, this approach must be exercised with caution. Combined GC-MS provides valuable structural information on each of the components separated, and permits identification of molecular modification.

Solar Panel Basics

Solar Panel Basics

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