Analytical techniques 1. GC-FID

At the ICTA-UAB lab, the gas chromatographic analyses were performed on an Agilent 7820A Gas Chromatograph fitted with a Flame Ionisation Detector (FID) using a DB-5 MS column (30 m length × 0.25 mm internal diameter × 0.25 μm stationary phase thick-ness). The splitless injector temperature was set at 300 °C and helium was used as the carrier gas. The temperature of the flame ionisation detector (FID) was 340 °C. The oven temperature was initially held at 50 °C for 2 min, then the temperature increased at 15 °C/min to 170 °C, and finally to 320 °C at 6 °C/min, and held for a further 46 min.

At the CEPAM lab, the gas chromatographic analyses were performed on an Agilent 7890A Gas Chromatograph fitted with a Flame Ionisation Detector (FID). 1μL was in-jected via an on-column injector, in order to maximize the amount of material inin-jected into the chromatograph and to avoid contamination by of septum compounds during high temperature analysis. The molecular compunds were separated into a DB-5 MS apolar capillary column (15 m length × 0.32 mm internal diameter × 0.1 μm stationary phase thickness). Hydrogen was used as the carrier gas. The temperature of the flame ionisation detector (FID) was 375 °C. The oven temperature was initially held at 50 °C for 2 min, then the temperature increased at 15 °C/min to 100 °C, and finally to 375 °C at 10 °C/min, and held for a further 46 min.

3.3.2. GC-MS

At the ICTA-UAB lab, the gas chromatography-mass spectrometry analyses were carried out using an Agilent 7890A Gas Chromatograph (GC) coupled to an Agilent 5975C Mass Spectrometer (MS). The GC was fitted with a DB-5 MS column (30 m length × 0.25 mm

123

internal diameter × 0.25 μm stationary phase thickness). The GC injector was operated in splitless mode and helium was used as the carrier gas. The temperature of the flame ionisation detector (FID) was 320 °C. The oven temperature was initially held at 50 °C for 2 min, then the temperature increased at 15 °C/min to 170 °C, and finally to 320 °C at 6 °C/min, and held for a further 46 min. The Mass Spectrometer was run in electron im-pact mode and masses were acquired in full scan mode between m/z 50 to m/z 800.

At the CEPAM lab, the gas chromatography-mass spectrometry analyses were carried out using a Shimadzu GC2010PLUS Gas Chromatograph (GC) coupled to an Shimadzu QP2010ULTRA Mass Spectrometer (MS), equipped with a quadrupole analyser and an electronic impact source (EI, Electron ionisation) at 70 eV. The GC was fitted with a DB-5HT column (15 m length × 0.32 mm internal diameter × 0.1 μm stationary phase thick-ness). The GC injector was operated in splitless mode and helium was used as the carrier gas. The temperature of the flame ionisation detector (FID) was 280 °C. The oven tem-perature was initially held at 50 °C for 2 min, then the temtem-perature increased at 15 °C/min to 100 °C, then to 240 °C at 10 °C/min, and finally to 380 °C at 20 °C/min. The Mass Spectrometer was run in electron impact mode and masses were acquired in full scan mode between m/z 50 to m/z 950.

3.3.3. GC-C-IRMS

In order to determine the compound-specific stable isotopic determination (C18:0 and C16:0), a third analysis is performed using a Delta V Thermo Fisher isotope ratio mass spectrometer (IRMS) hyphenated to a Trace GC Thermo Fischer Scientific gas chromato-graph via a combustion interface (GC). The GC is fitted with a DB-5 MS-UI (60 m × 0.25 mm × 0.25 μm) column. The injector temperature is set at 310 °C. The oven is initially held at 80 °C for 1 min, then ramp at 30 °C/min to 120 °C, and finally increased to 320 °C at 6 °C/min and held for 21 min. Helium is used as the carrier gas. The com-bustion reactor is set at 940 °C.

124

Data is acquired and analysed using ISODAT 3.0 software. Analytical accuracy is con-firmed by running fatty acid methyl ester (FAME) and alkane standards of known iso-topic values prior to each batch of analysis. During each run, three pulses of carbon di-oxide of known isotopic composition are fed into the ion source from the reference gas injector. These measures ensured that the instrument and combustion furnace are func-tioning correctly. Instrument precision is ±0.3‰.

The carbon isotope ratios are relative to the standard reference material vPDB, δ¹³C

‰ = [Rsample − Rstandard]/Rstandard. The δ¹³C values were corrected for the carbon atoms added during methylation using the following equation: δ¹³CFA = ((nCFAME) × δ¹³CFAME) − δ¹³CMeOH)/n, where δ¹³CFA is the corrected value for the fatty acid, n is the carbon chain length, nCFAME is the total number of carbon atoms in the FAME (n + 3 for TMS ester and n + 1 for methyl ester), δ¹³CFAME is the value measured for the fatty acid methyl ester of carbon chain length n, and δ¹³CMeOH is the correction factor for the derivatising agent.

Both correction factors were obtained by derivatising a known δ¹³CFA value with each of the derivatising agents (BSTFA and H2SO4-MeOH).

3.3.4. TLE quantification

To quantify the total lipid extraction of each of the peaks appearing in the GC-FID gen-erated chromatogram, the area of each peak was calculated and quantified from the internal standard (IS) using this formula: [sample area / IS area * weight IS/weight power ceramic sample], omitting contaminant peaks such as plasticizers.

3.4. Pottery analysis

The study of vessel morphology and morphometry, together with biochemical analyses of contents, can provide information about use habits, i.e. the amount of food prepared and stored, the selection of certain types of sherds for specific purposes. The interpre-tation of the results points to economic and social behaviours related to food consump-tion and conservaconsump-tion (Arthur, 2002; Skibo, 1992, 2013; Vieugué et al. 2008).

125

In the macroscopic analysis of the ceramic fragments studied, the different morpholo-gies of vessels (hemispherical, ovoidal, ellipsoidal) and the mouth opening (divergent, straight, incoming), as well as the metric characteristics (thickness of the walls, opening of the vessel and type of lip) and the presence of handles were taken into account. These characteristics form key elements for understanding vessel function. However, not all the assemblies had sufficient conservation of the ceramic profiles to be able to catego-rise this function.

Of the 9 archaeological sites studied, a total of 62 ceramic containers from Camp del Colomer, Carrer Llinàs 28, Feixa del Moro, Mines de Gavà and Cueva de El Toro were classified into 6 categories according to their presumed function. Following the proposal of functional classification of Rice (2015) and Skibo (2012) from morphological and mor-phometrical data.

The morphological and morphometric study of vessels was governed by the following criteria already proposed in previous similar studies (Fanti et al. 2018):

Type of profile: simple, carinated, inflected, necked.

▪ Openess ratio (rim diameter/tangential diameter). >1: open, =1: restricted, 0.50-0.99: closed, <0.5: very closed.

▪ Depth (maximum diameter/height). >1.5: shallow, 0.76-1.5: medium deep, 0.51-0.75: deep, 0.25-0.5: very deep.

▪ Volume.

▪ Presence of handles.

126

Measuring the capacity of a container is not always possible, especially because whole archaeological vases are quite rare, and the fragments found do not always make it pos-sible to account for them. In order to calculate the volume of vessels of different shapes and sizes, the following process was followed: initially n-measurements were taken (ac-cording to the size of the vessel) of the distance between the axis of symmetry of the vessel and its outer wall (R); then the height was also taken (distance from point A to point B). With these points the curve of the vessel profile is made; using a polynomial of degree p (p=3 to 6) approximates the function: f(r); the degree of the polynomial can vary to get a better approximation (R2≈1). Once the function f(r) is obtained, by means of the complete revolution (Θ=2π rad) of the area between the f(r) and the axis of sym-metry, the value of the volume of the vessel is obtained (cylindrical coordinates were used for this calculation) (Figure 3.3).

Figure 3.3. Variables drawing (left) and volume calculation formula (right).