Sample preparation of archaeological materials for PIXE analysis

A method to prepare thin samples of archeological materials such as potteries and bones for PIXE analysis is presented. In this method fine powder of the matter under analysis is suspended and deposited on polycarbonate filters. The process takes place in a chamber where clean air and the powder are mixed and forced to pass through the filter. Thin samples with typical mass density of about 50 μg cm^-2 are obtained. The uniformity of the mass deposit has been optically tested with a He-Ne laser showing fluctuations of the order of one percent. Samples of clay standards from NIST were prepared with this method and analyzed by PIXE. The agreement between our results and NIST values is very good, with linear correlation factors close to unity. The method was applied to study the elemental composition of clay from different fragments of a Chilean pre-Hispanic pottery piece. These results are very consistent showing that the analysis of samples from a small fragment can represent the whole piece.