GC-MS Analysis of Amphorae and Cooking Ware from Miletus (Western Asia Minor)

Two extractions protocols have been applied in order to extract lipids according to Pecci et al. 2013 (a), and other small organic acids according to Pecci et al. 2013a (b). a. 2 g samples are extracted in 50 ml chloroform/methanol (2:1 v/v) for 2×15 min in an ultrasonic bath. The samples are then centrifuged for 10 min and the supernatant is concentrated down to approx. 1 ml. The residue is evaporated to dryness under a steady stream of nitrogen. The samples are saponified with 2 ml sodium hydroxide solution (2M in MeOH) for 1 h at 70° C. and after cooling, acidified with 15 drops of concentrated hydrochloric acid, the pH value is checked (pH 1). It is then extracted twice with 3 ml of chloroform; the solvent is removed under a constant stream of nitrogen and the sample is transferred to a vial with two times 50 μl of chloroform. The solvent is then evaporated off and the sample is derivatized with 25 μl of BSTFA at 70° C. for 1 hour. After the addition of 75 µl n-hexane and 5 µl internal standard (dotriacontane, see respective table of results for concentration)), the samples are analyzed by GC-MS. b. 500 mg sample is extracted in 3 ml potassium hydroxide solution (1M in H2O) for 90 min at 70°C. The samples are then centrifuged for 10 min and the supernatant is acidified with 15 drops of concentrated hydrochloric acid, and the pH value (pH 1) is checked. Then the samples are shaken intensively with 3 ml ethyl acetate for 2 min and centrifuged for 10 min. This step is done 3 times. The supernatant is concentrated under a constant stream of nitrogen and transferred to a sample vial with two 50 μl portions of ethyl acetate. The solvent is then evaporated off and the sample is derivatized with 25 μl of BSTFA at 70° C. for 1 hour. After the addition of 75 µl n-hexane and 5 µl internal standard (dotriacontane, see respective table of results for concentration), the samples are analyzed by GC-MS. The GC-MS analyses have been performed using an Agilent Technologies 5977E MSD with 7820A GC, with a 30 m HP-5 MS separation column (also Agilent Technologies). Pecci et al. 2013 A. Pecci – M.A. Cau – N. Garnier, Identifying wine and oil pro- duction: analysis of residues from Roman and Late Antique plastered vats, Journal of Archaeological Science 40, 4491–4498 Pecci et al. 2013a A. Pecci – G. Giorgi – L. Salvini – M.A. Cau Ontiveros, Identifying Wine Markers in Ceramics and Plasters with Gas Chromatography-Mass Spectrometry. Experimental and Archaeological Materials, Journal of Archaeological Science 40, 109–115