Comparative analysis of X-ray fluorescence methods for elemental composition determination of the archaeological ceramics from low sample quantity

Abstract

Wavelength-dispersive X-ray fluorescence analysis (WDXRF) and total-reflection X-ray fluorescence (TXRF) analysis were applied to study the elemental composition of the Late Neolithic ancient ceramics collected at the Popovsky Lug burial site (Kachug, Upper Lena river, Russia). Semi-quantitative non-destructive analysis of ceramic pieces showed that measurements of the upper and lower sides of the ceramic are less informative than the measurement of its cut. Various sample preparation techniques for the low quantity of crushed ceramics such as fusion, pressing and preparation of suspensions were compared to preserve the material. Samples were prepared as 150 mg fused beads and 250 mg pressed pellets for WDXRF, and as suspensions of 20 mg sample based on the aqueous solution of the Triton X-100 surfactant for TXRF. Certified methods were used to validate the obtained contents of rock-forming oxides and inductively coupled plasma mass spectrometry was used to confirm the results of trace elements determination. Based on the carried-out studies, a combination of the wavelength-dispersive X-ray fluorescence analysis (glass) and total-reflection X-ray fluorescence analysis (suspension) methods was chosen to obtain the data on the elemental bulk composition of archaeological ceramics. The proposed combination allowed the quantitative determination of Na, Mg, Al, Si, P, K, Ca, Ti, Mn, Fe, V, Cr, Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr, Pb, and Ba from the sample of crushed ceramics weighing only about 170 mg.

A Workflow for Uncertainty Assessment in Elemental Analysis of Archaeological Ceramics: A Case Study of Neolithic Coarse Pottery from Eastern Siberia

“…According to the petrographic analysis of thin sections [26], the mineral composition of different ceramic types from this region is very similar and varies in the following ranges: clay (73-93%), quartz (5-20%) with a grain size of 3 to 0.1 mm, feldspar (1-14%) with a grain size of 1-0.1 mm, and mica (no more than 1%). Other minerals in thin sections include calcite, single inclusions of epidote, ilmenite, hematite, magnetite, limonite, and zircon.…”

“…To date, our research group has carried out studies of the mineral and elemental compositions of pottery from the Popovsky Lug archaeological site located in the valleys of Upper Lena River, Eastern Siberia, Russia [14,17,18,26]. This is a multilayered site containing cultural deposits of various Neolithic stages [27].…”

“…Ceramic is among the most complex archeological materials because it consists of clay minerals, non-plastic inclusions, and intentionally added tempers in different proportions. For archaeological ceramics, quantitative elemental analysis can be performed by means of analyzing dry, powdered, and homogenized ceramic fragments using instrumental neutron activation analysis (INAA) [4][5][6], inductively coupled plasma mass spectrometry (ICP-MS) [7][8][9], conventional X-ray fluorescence spectrometry (XRF) [7,[10][11][12][13][14], and total reflection XRF [14][15][16][17][18]. It is evident that the pulverization and thorough mixing of large ceramic fragments provide a homogeneous representative sample for further elemental analysis.…”

“…Then, a mixture of calcined sample weighing 110 mg, 1.1 g of extra-pure lithium metaborate and 7 drops of 40 mg/mL LiBr solution was fused in a platinum crucible in the electric furnace TheOX (Claisse, Québec, QC, Canada) at 1050 • C for 19 min to prepare glass disks with a diameter of 10-12 mm[31]. This technique was previously successfully applied to the elemental XRF analysis of bottom sediments and ancient ceramics[14,32]. Certified reference materials (CRMs) were used to construct calibration curves and control the accuracy, namely silts (BIL-1, BIL-2, SGH-1, SGH-3, SGH-5), loose sediments (SGHM-1, SGHM-2, SGHM-3, SGHM-4), aleurolite (SA-1), clays, slits, and ooze (SDO-1, SDO-2, SDO-8, SDO-9), provided by the Vinogradov Institute of Geochemistry and Research Institute of Applied Physics from Russia; CRMs of sedimentary rocks (JSD-1, JSD-2, JSD-3, JLK-1) were provided by the Geological Survey of Japan; CRMs CH-1 (marine sediment, GeoPT-10), UoK Loess (Köln loess, GeoPT-13), SdAR-1 (modified river sediment, GeoPT-31), and DBC-1 (clay, GeoPT-33) were provided by the International Association of Geoanalysts; •…”