RESEARCH PAPER An alternative analytical method based on ultrasound micro bath hydrolysis and GC-MS analysis for the characterization of organic biomarkers in archaeological ceramics Laura Blanco-Zubiaguirre 1 & Maitane Olivares 1 & Kepa Castro 1 & Javier G. Iñañez 2,3 & Juan Manuel Madariaga 1 Received: 19 May 2016 /Revised: 20 July 2016 /Accepted: 23 August 2016 # Springer-Verlag Berlin Heidelberg 2016 Abstract The analysis of organic biomarkers in ancient and valuable archaeological remains provides a worthwhile source of information regarding their management. This work was focused on the development of an analytical procedure to characterize organic residues that have remained in archaeo- logical ceramic samples. A novel analytical approach based on an alkaline hydrolysis by means of an ultrasound micro bath followed by liquid extraction was proposed to isolate saturated and unsaturated fatty acids, degradation products such as dihydroxy acids or dienoic fatty acids, isoprenoid fatty acids, and many other biomarkers from archaeological re- mains. This main goal has been achieved after the optimiza- tion of the main parameters affecting the hydrolysis step, the extraction procedure, and the derivatization step prior to the gas chromatography–mass spectrometry analysis. In this work, archaeological ceramic remains suspected to have been used by Basque Whalers to store whale oil in the period from the sixteenth to the seventeenth century were studied. Nevertheless, the proposed method is useful to determine the organic remains preserved in many other archaeological ce- ramic remains. Moreover, this methodology can be used to determine organic remains in any porous ceramic, archaeological or not. The preliminary results of the analysis of ceramic vessels led to the determination of some interesting unsaturated compounds such as 11-eicosenoic acid, an impor- tant biomarker of marine commodities, and several saturated fatty acids, which could be indicative of having used the ves- sels to store whale oil. Keywords Fatty acids . Archaeological organic remains . Ultrasound micro bath . Gas chromatography–mass spectrometry Introduction Analytical research in the field of organic archaeological res- idues found in ancient vessels has grown into a recognized field in its own right and has developed rapidly in recent decades. The characterization of such residues has led to the clarification of several aspects of daily life related to diet, trade, rituals, and so on [1–3]. Those residues can survive as actual contents preserved in situ as vessel fills (rarely ob- served), surface residues appearing as visible residues on the interior or exterior of vessels or absorbed residues preserved within the vessel wall, invisible to the naked eye, the latter being the most common category [4]. Organic residues can remain for a long time in ceramic pottery, mainly absorbed in the porous matrix. The analysis of organic remains in these potsherds offers an insight into vessel use, site, and regional economies and technologies. Among the wide range of investigated compounds, lipids and their transformation products have been the most widely studied ones due to the wide use of animal fats and oils of various nature and origin in the past and their relative stability [5, 6]. Marine animal fats are easily distinguished from mod- ern terrestrial ones through their lipid profiles, the former’ s * Laura Blanco-Zubiaguirre laura.blanco@ehu.eus 1 Department of Analytical Chemistry, Faculty of Science and Technology, University of the Basque Country (UPV/EHU), P.O. Box 644, 48080 Bilbao, Spain 2 Department of Geography, Prehistory and Archaeology, University of the Basque Country (UPV/EHU), 01006 Vitoria-Gasteiz, Araba, Spain 3 IKERBASQUE, Basque Foundation for Science, Maria Diaz de Haro 3, 48013 Bilbao, Spain Anal Bioanal Chem DOI 10.1007/s00216-016-9898-9