THE APPLICATION OF SYNCHROTRON RADIATION TO MICROPROBE TRACE-ELEMENT ANALYSIS OF BIOLOGICAL SAMPLES

An X-ray fluorescence microprobe (XRM) for trace-element analysis is in operation at the National Synchrotron Light Source of Brookhaven National Laboratory. The properties of synchrotron radiation, in this case a continuous spectrum of X-rays ranging up to 40 keV, make possible its use as a microprobe beam with collimation or focusing with appropriate optical elements. Sensitivities in thin samples at 10 × 10 μm2 spatial resolution is of the order of 10 fg using filtered, collimated "white light" and about 3 fg using a Kirkpatrick-Baez (KB) focusing system in thin standard foil. Results using a newly installed ellipsoidal mirror will be described. A discussion of standards for microprobe analysis is included. Examples of applications to the life sciences are described. These include the mapping of trace-element distributions in thin tissue samples and examples of transmission and fluorescence microtomography. Synchrotron radiation microprobes complement ion and electron beam microprobes and the differences between the methods are considered. © 1990.