Sensitivity calculations for multielemental trace analysis by synchrotron radiation induced X-ray fluorescence

Abstract

The application of synchrotron radiation from high energy electron storage rings as an excitation source for X-ray fluorescence analysis of trace elements will greatly extend the sensitivity of the fluorescence technique. The properties of synchrotron radiation that make improvement possible are: high brightness, continuously tunable energy spectrum, relatively low energy deposition, and polarization in the storage ring plane for reduced scattering backgrounds. New wide energy bandwidth monochromators now being developed will provide intense monochromatic beams which will make practical the use of the wavelength dispersive crystal spectrometers. The sensitivity calculations presented are applied to representative thin biological and geological samples. The storage ring parameters used are the design parameters of the National Synchrotron Light Source. The quantitation limits ( σ=10%) for a thin biological sample using a solid state detector is less than 1 ppm for low Z elements and 1–10 ppm for high Z elements for one minutev irradiations. Using fixed multicrystal wavelength dispersive spectrometers quantitation limits range from 3–30 ppb for biological samples and 30–300 ppb for geological samples. Minimum detectable limits are a factor of 3 to 5 lower.