pXRF method development for elemental analysis of archaeological soil

Portable X-ray fluorescence (pXRF) is now widely used for detecting the elemental composition of a material. Elemental analysis can enhance archaeological interpretations, such as mapping, preservation analysis and identifying anthropogenic activities. However, validated and reproducible protocols for analysing archaeological soil are still required. The elemental concentrations detected with three sets of preparation methods were compared: in-situ (no preparation), in-field (analysing through plastic bags) and ex-situ analysis (laboratory-based preparation). Influential factors were also investigated: calibration parameter, moisture, homogeneity, sieve size and soil type. In-field analysis attempted to improve reliability without offsite processing, but instead substantially reduced elemental concentrations and skewed the proportional distributions. Ex-situ analysis significantly increased elemental concentrations and reduced variation. Proportional distribution was different between the three methods, but unchanged following homogenizing and sieving. These comparisons demonstrated that ex-situ analysis maximizes detection and ensures consistent samples.