Trace element determinations using a 15-keV synchrotron x-ray microprobe

Abstract

At the Synchrotron Radiation Source (SRS), Daresbury, U.K., a synchrotron microprobe was constructed, in order to create an instrument capable of analyzing at the ppm or in favorite cases sub-ppm level with a lateral resolution of 10 x 15 microns2. In order to span a wide range of elements to be analyzed, a beam energy of 15 keV was chosen. Focusing and monochromation of the white beam was done in one single step with a high-precision ellipsoidally concave curved Si(111) crystal. Sufficient flux of X-rays in a narrow energy band is available in the spot to measure trace elements at the femtogram level. Measurements on standard materials, reference standard materials, and biological samples showed the lower relative minimum detection limits and higher sensitivity for the higher Z-elements obtainable with micro-SXRF (synchrotron X-ray fluorescence) as compared with microtechniques using ion accelerators. Moreover, the much lower energy deposited in the specimen represents a major argument to prefer X-rays to ions for the analysis of radiation-sensitive samples.

Synchrotron Radiation Spectroscopic Techniques as Tools for the Medicinal Chemist: Microprobe X-Ray Fluorescence Imaging, X-Ray Absorption Spectroscopy, and Infrared Microspectroscopy

“…[5,[16][17][18] Detection sensitivities have been reported in the ppb range, with values of 10 17 g -10 14 g (depending on the particular element) cited for analysis of samples as small as individual mammalian (or even bacterial) cells.…”

“…[6, [16][17][18][19][20][21][22] The physical process of XRF spectroscopy (Figure 1) involves the use of a beam that possesses an energy high enough to excite the atoms of all the elements of interest (i.e., higher than the binding energy of the core electron of the element, generally K and L shells). [6][7] When the beam strikes the sample and a core electron is ejected into the continuum, an unstable ion is produced.…”

Metallomics, elementomics, and analytical techniques

“…If the exciting source is replaced by a high-energy proton beam, it will be called proton-induced X-ray emission spectrometry (PIXE) [56], which can provide better analytical sensitivity than XRF. If synchrotron radiation (SR) is used as exciting source, the SR-XRF will achieve an absolute detection limit of 10 -12 -10 -15 g and relative detection limit of several µg/g, even in ng/g levels [57]. XRF is basically a qualitative technique, but quantification can also be achieved [58,59].…”

“…The major limitation for the application of Mössbauer spectroscopy in biological samples is that only a few isotopes can be used. The most commonly used isotope is 57 Fe, which has been used for the study of ferritins in biological samples, but the low content and natural abundance of Fe may hinder its application [195].…”

Comparison of a portable micro-X-ray fluorescence spectrometry with inductively coupled plasma atomic emission spectrometry for the ancient ceramics analysis

“…Synchrotron micro-XRF has the advantage of offering intense radiation; it is often used in XRF microprobe analysis of ancient ceramics, but it requires big and expensive facilities [15,16]. On the other hand, laboratory micro-XRF instruments can operate with either X-ray tubes or radioisotopic sources.…”