Dr. Danielle Kurin is a former assistant professor and tenuredassociate professor of anthropology at the University of California at Santa Barbara who has trained graduate and undergraduate students in various elemental, compositional, and histological preparation of samples, as well as analysis of human tissues using multiple techniques such as pXRF, isotopy, and 3D morphometrics. Dr. Kurin has used these methods in her own research work in the Andes of Peru, to understand ecological adaptation, the movement of populations, and health and disease in the period from about 1000 to 1400 AD. She has also used these techniques on contemporary human remains to help identify the home regions of victims of violence during such conflicts as between the Army and the Shining Path.
A nondestructive method used for elemental analysis of samples, XRF spectrometry is based on the principle of absorption of energy of atoms when the surface of a substance is bombarded with x-rays. It is useful in analyzing a wide variety of samples including rocks, bones, ceramic paints, and soil samples. XRF spectrometry works by causing ejection of electrons from the inner shell of an atom, which results in the subsequent replacement of the ejected electron by a more energetic electron from any outer shell. This results in dispersion of x-ray photons whose value is equal to the difference in energy levels between the resting electron and the ejected electron. Detecting and measuring the energies of the photons can be used to determine the elemental components of samples.
There are two primary types of XRF spectrometers, the wavelength-dispersive (WD) spectrometer and the energy dispersive (ED) spectrometer. All ED XRF spectrometers use semi-conductor type detectors that collect emitted spectrum from a sample, and decode the received spectrum into a number of count per photon energy histogram. WD XRF spectrometers, on the other hand, make use of a crystal to disperse the emitted photons depending on the wavelength of each photon, and the dispersed photons are received by a detector that measures x-rays of that particular wavelength.
In past years, XRF spectrometers have been of limited use to archaeologists due to the limited size of the sample they could analyze, because the material has to be mounted on the instrument. Samples like large rocks may be impossible to analyze unless broken, which is not practical if sample preservation is desired. However, the invention of portable XRF (pXRF) solved this problem – it allows the convenient and quick analysis of samples.
Danielle Kurin 