Anal. Chem. 1988, 58,2167-2171
2167
Synchrotron X-ray Fluorescence: Diffraction Interference S. R. Sutton,*’ M. L. Rivers,’ and J. V. Smith Department of the Geophysical Sciences, University of Chicago, Chicago, Illinois 60637
Synchrotron X-ray fluorescence (SXRF) is valuable for rapid, nondestructive trace element analysis of geological and biological specimens with minimum detection limits of 10-100 parts per billion weight for 20-hm spots. X-ray diffraction is a slgnificant interference in SXRF analysis of Well-ordered specimens. It depends on excitation source (continuum or monochromatic), detection system (energy or Wavelength dispersive), and specbnen orientation. The most pronounced effects occur for synchrotron continuum and energydlspersive detectors: thus, the probaMltty of observing diffraction peaks from a randomly oriented quartz crystal is near unity. Diffraction peaks were observed in X-ray fluorescence spectra from silicon, quartz, and deep sea particles at the National Synchrotron Llght Source (Brookhaven National Laboratory, Upton, NY). Scattering peaks were observed from silica glass. Identilicatkm of diffraction effects Is best accomplished by changing the specimen orientation since diffraction features are modifled while fluorescence lines remain unaltered.
Synchrotron X-ray fluorescence (SXRF) permits rapid, nondestructive trace-element analysis of geological and biological specimens with minimum detection limits of 10-100 parts per billion weight (ppbw) for 20-pm spots (ref 1-3 and references therein). High sensitivity results from the special nature of the synchrotron radiation. For a bending magnet of a dedicated X-ray storage ring, the small source size (