Analysis of archaeological triacylglycerols by high resolution nanoESI, FT-ICR MS and IRMPD MS/MS: Application to 5th century BC-4th century AD oil lamps from Olbia (Ukraine)

This work presents the precise identification of triacylglycerols (TAGs) extracted from archaeological samples using a methodology based on nanoelectrospray and Fourier transform mass spectrometry. The archaeological TAG identification needs adapted sample preparation protocols to trace samples in advanced degradation state. More precisely, the proposed preparation procedure includes extraction of the lipid components from finely grinded ceramic using dichloromethane/methanol mixture with additional ultrasonication treatment, and TAG purification by solid phase extraction on a diol cartridge. Focusing on the analytical approach, the implementation of "in-house" species-dependent TAG database was investigated using MS and InfraRed Multiphoton Dissociation (IRMPD) MS/MS spectra; several vegetal oils, dairy products and animal fats were studied. The high mass accuracy of the Fourier transform analyzer ([Delta]m below 2.5 ppm) provides easier data interpretation, and allows distinction between products of different origins. In details, the IRMPD spectra of the lithiated TAGs reveal fragmentation reactions including loss of free neutral fatty acid and loss of fatty acid as [alpha],[beta]-unsaturated moieties. Based on the developed preparation procedure and on the constituted database, TAG extracts from 5th century BC to 4th century AD Olbia lamps were analyzed. The structural information obtained succeeds in identifying that bovine/ovine fats were used as fuel used in these archaeological Olbia lamps.