Reference-free trace element determination by TXRF

Dr. B. Beckhoff (Physikalisch-Technische Bundesanstalt, Berlin, Germany) and his colleagues have successfully performed a reference-free quantitation by total reflection X-ray fluorescence (TXRF) analysis in the soft X-ray region. So far, element determination by XRF has been usually done with a calibration curve, which requires some reference samples. However, there have been increasing demands for reference-free analysis, particularly in cases where stable and reliable reference samples are not easily obtained. The fundamental parameter method, which is one of the most promising ways of performing such reference-free analysis, uses the theoretical XRF intensity expressed by Sherman's equation (or Fujino-Shiraiwa's formula), but appears to be highly dependent on geometrical factors, the spectral distribution of primary X-rays, and atomic fundamental constants etc. In TXRF, the intensity is affected by additional conditions. The experiments were done with monochromatic synchrotron radiation, at BESSY II. The research group has developed a feasible sample chamber specially designed for quantitative XRF. In addition, several calibrated detector systems have been employed to obtain reliable results. For more information, see the paper, "Reference-Free Total Reflection X-ray Fluorescence Analysis of Semiconductor Surfaces with Synchrotron Radiation", B. Beckhoff et al., Anal. Chem. 79, 7873 -7882 (2007).