Study of binding media in works of art by gas chromatographic analysis of amino acids and fatty acids derivatized with ethyl chloroformate

The aim of this work is to identify proteinaceous and oil binding media used in paintings from art collections in the Region of Valencia (Spain). This information is extremely useful for conservation and restoration work. The proposed procedure involves protein and glyceride hydrolysis from sub-milligram samples by treatment with hydrochloric acid, followed by neutralization, partition with chloroform and derivatization with ethyl chloroformate (ECF) of both the aqueous and the organic phases. The ECF derivatives of amino acids and azelaic, myristic, palmitic and stearic acids are separated by capillary gas chromatography. Amino acids are mainly found in the aqueous phase and long chain fatty acids in the organic phase. The distribution of azelaic acid was approximately similar in the two phases. Amino acid and fatty acid ratios found proved extremely useful for identifying the binding media in the paintings analysed. (C) 1997 Elsevier Science B.V.