An analytical procedure based on alkaline hydrolysis and silylation followed by GC/MS analysis was employed to study the formation of characteristic acidic compounds and the development of a distinctive chromatographic pattern in the course of accelerated ageing tests on Brassicaceae seed oil. On the basis of mass spectra of trimethylsilyl derivatives, the main degradation products were identified as ,-dicarboxylic, -hydroxycarboxylic and dihydroxycarboxylic acids, including 11,12-dihydroxyeicosanoic acid and 13,14-dihydroxydocosanoic acid. The mass spectra of these both compounds are characterised by fragment ions arising from the cleavage of the bond between the two vicinal trimethylsiloxy groups, resulting in fragments at m/z 215 and 345 for 11,12-dihydroxyeicosanoic acid, and at m/z 215 and 373 for 13,14-dihydroxydocosanoic acid. Other significant fragment ion-radicals from rearrangement process at m/z [M-90]+∙, [M-142]+∙, 204 as well as fragment ions at m/z [M-15]+, [M-105]+, 217 are present in the mass spectra of both the compounds. The results obtained for reference materials were compared with those relating to archaeological organic materials recovered in Egyptian pottery lamps. The occurrence of the same characteristic degradation products found in the reference materials subjected to accelerated aging indicates an unambiguous origin for the organic archaeological remains and represents the chemical evidence for the use of oil from seeds of Brassicaeae as illuminant.
Organic mass spectrometry in archaeology: evidence for Brassicaceae seed oil in Egyptian ceramic lamps
COLOMBINI, MARIA PERLA;MODUGNO, FRANCESCA;RIBECHINI, ERIKA
2005-01-01
Abstract
An analytical procedure based on alkaline hydrolysis and silylation followed by GC/MS analysis was employed to study the formation of characteristic acidic compounds and the development of a distinctive chromatographic pattern in the course of accelerated ageing tests on Brassicaceae seed oil. On the basis of mass spectra of trimethylsilyl derivatives, the main degradation products were identified as ,-dicarboxylic, -hydroxycarboxylic and dihydroxycarboxylic acids, including 11,12-dihydroxyeicosanoic acid and 13,14-dihydroxydocosanoic acid. The mass spectra of these both compounds are characterised by fragment ions arising from the cleavage of the bond between the two vicinal trimethylsiloxy groups, resulting in fragments at m/z 215 and 345 for 11,12-dihydroxyeicosanoic acid, and at m/z 215 and 373 for 13,14-dihydroxydocosanoic acid. Other significant fragment ion-radicals from rearrangement process at m/z [M-90]+∙, [M-142]+∙, 204 as well as fragment ions at m/z [M-15]+, [M-105]+, 217 are present in the mass spectra of both the compounds. The results obtained for reference materials were compared with those relating to archaeological organic materials recovered in Egyptian pottery lamps. The occurrence of the same characteristic degradation products found in the reference materials subjected to accelerated aging indicates an unambiguous origin for the organic archaeological remains and represents the chemical evidence for the use of oil from seeds of Brassicaeae as illuminant.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
