GC-MS analyses of ceramic samples from Busa delle Vette (Parco delle Dolomiti Bellunesi, Belluno Province, Veneto, Northern Italy)

The organic residue analyses were carried out at the core facillity BioSupraMol of the departement of Biology, Chemistry, and Pharmacy (Freie Univ. Berlin). Two extractions protocols have been applied in order to extract lipids (Pecci et al. 2013 [A]), and other small organic acids (Pecci et al. 2013a [B]) from the powdered ceramic samples. 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 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. After cooling, it is 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. Then the solvent of the organic phase is removed under a constant stream of nitrogen and the sample is transferred to a sample vial with two times 50 μl of chloroform. The sample 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 in hexane, see respective table of results for concentration), the samples are analysed 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 repeated 3 times in total. The supernatant (organic phase) 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 in hexane, see respective table of results for concentration), the samples are analysed by GC-MS. All samples were analysed using Agilent 7820A GC system and Agilent 5977 MSD, equipped with HP5-MS capillary column and EI as ion source. Initial oven temperature 50°C with a temperature ramp of 5 °C/min to 320 °C and hold time of 10 min. For this method a split ratio of 1:10 has been used. Pecci, A., Cau, M.A., Garnier N., Identifying wine and oil pro- duction: analysis of residues from Roman and Late Antique plastered vats. Journal of Archaeological Science, 40, 2013, 4491–4498 Pecci, A., G. Giorgi, L. Salvini, Cau Ontiveros M.A., Identifying Wine Markers in Ceramics and Plasters with Gas Chromatography — Mass Spectrometry. Experimental and Archaeological Materials. Journal of Archaeological Science 40, 2013a, 109–115