Combining TXRF, FT-IR and GC-MS information for the identification of inorganic and organic components in black pigments of rock art from Alero Hornillos 2, (Jujuy, Argentina)

VÁZQUEZ CRISTINA; MAIER MARTA; PARERA SARA D.; YACOBACCIO HUGO; SOLÁ PATRICIA

Analytical and Bioanalytical Chemistry

Año: 2008 vol. 391 p. 1381 - 1387

Archaeological samples are complex in composition since they generally comprise a mixture of materials submitted to deterioration factors largely dependent on the environmental conditions. Therefore, the integration of analytical tools such as TXRF, FT-IR and GC-MS can maximize the amount of information provided by the sample. Recently, two black rock art samples of camelid figures at Alero Hornillos 2, an archaeological site located near the town of Susques (Jujuy Province, Argentina), were investigated. TXRF technique, selected for inorganic information, showed the presence of manganese and iron among other elements, consistent with an iron and manganese oxide as the black pigment. Aiming at the detection of any residual organic compounds, the samples were extracted with a chloroform/methanol mixture and the extracts were analyzed by FT-IR, showing the presence of bands attributable to lipids. Analysis by GC-MS of the carboxylic acid methyl esters prepared from the sample extracts, indicated that the main organic constituents were saturated (C16:0 and C18:0) fatty acids in a relative abundance characteristic of a degraded animal fat. The presence of minor C15:0 and C17:0 fatty acids as well as branched-chain iso-C16:0 pointed to a ruminant animal source.