W.M. Kwiatek

Trace element measurements using white synchrotron radiation

Abstract Synchrotron radiation, when used for X-ray fluorescence (XRF) has several advantages over conventional X-ray sources. Our group at Brookhaven National Laboratory is developing the equipment and expertise to make XRF measurements with synchrotron radiation. The apparatus is briefly described, along with the alignment techniques. Some minimum detectable limits for trace elements in thin biological standards measured with white light irradiations are presented.

Nonpolynomial approximation of background in X-ray spectra☆

Abstract A simple method for the calculation and subtraction of background from Si(Li) X-ray spectra prior to their least-squares fitting is described. Its properties are discussed and examples of its usage are shown.

X-RAY FLUORESCENCE WITH SYNCHROTRON RADIATION

The use of synchrotron radiation for X-ray fluorescence has several advantages over the use of other conventional X-ray sources. The principles of synchrotron radiation and methods for applying synchrotron radiation to the X-ray fluorescence measurements of trace elements are discussed. The Brookhaven National Laboratory X-ray microprobe, facilities dedicated to X-ray fluorescence, and related analytical techniques are discussed. Some examples of trace element analyses in biological materials with synchrotron radiation are presented.

Elemental concentrations in bones from an ancient egyptian mummy and from a contemporary man

Abstract Differences in elemental concentrations in bones taken from an ancient Egyptian mummy and a contemporary man were investigated by using proton induced X-ray emission (PIXE) in combination with Rutherford backscattering (RBS). Remarkable differences were noticed in the Fe/Ca and Pb/Ca relative concentrations, which were consistently higher in the contemporary man.

Trace element distribution in the rat cerebellum

Abstract Spatial distributions and concentrations of trace elements (TE) in the brain are important because TE perform catalytic and structural functions in enzymes which regulate brain function and development. We have investigated the distributions of TE in rat cerebellum. Structures were sectioned and analyzed by the Synchrotron Radiation Induced X-ray Emission (SRIXE) method using the NSLS X-26 white-light microprobe facility. Advantages important for TE analysis of biological specimens with X-ray microscopy include short time of measurement, high brightness and flux, good spatial resolution, multielemental detection, good sensitivity, and nondestructive irradiation. Trace elements were measured in thin rat brain sections of 20 μm thickness. The analyses were performed on sample volumes as small as 0.2 nl with Minimum Detectable Limits (MDL) of 50 ppb wet weight for Fe, 100 ppb wet weight for Cu, and Zn, and 1 ppm wet weight for Pb. The distribution of TE in the molecular cell layer, granule cell layer and fiber tract of rat cerebella was investigated. Both point analyses and two-dimensional semiquantitative mapping of the TE distribution in a section were used. All analyzed elements were observed in each structure of the cerebellum except mercury which was not observed in granule cell layer or fiber tract. This approach permits an exacting correlation of the TE distribution in complex structure with the diet, toxic elements, and functional status of the animal.

Selection of the experimental conditions for white-light SRIXE measurements

Abstract Synchrotron-radiation-induced X-ray emission has enormous potential as a technique for trace-element analysis. To fully utilize the many advantages of SRIXE measurements, one must optimize the experimental conditions. In this paper the problems associated with the selection of experimental conditions are discussed in theory. In addition, examples of experimental work done at the National Synchrotron Light Source at Brookhaven National Laboratory, USA are presented.

Correlation of trace elements in hair of patients with colon cancer

Abstract The trace element content of 116 hair samples from patients with colon cancer and from referent series of patients who had a variety of other diseases were measured using proton-induced X-ray emission (PIXE). The patients had been on largely uncontrolled diets, and the interest was whether there were differences in trace element concentrations attributable to the effects of colon cancer. The concentrations of K, Ca, Mn, Fe, Cu, Zn, Se, Br, and Rb were determined using a beam of 2.5-MeV protons. Minimum detectable limits (MDL) of 0.3 ppm were obtained for Zn and Se. Cluster analysis of the data set did not reveal any significant differences between the cancer and control groups. Mean values and ranges obtained for the elemental concentrations show good agreement with other published determinations.

The use of a SiTek position sensitive detector for synchrotron radiation beam monitoring and alignment

Abstract A SiTek Laboratories one-dimentional position sensitive detector has been tested for use as a synchrotron radiation beam position monitor.

The Role of High-Energy Synchrotron Radiation in Biomedical Trace Element Research

This paper will present the results of an investigation of the distribution of essential elements in the normal hepatic lobule. the liver is the organ responsible for metabolism and storage of most trace elements. Although parenchymal hepatocytes are rather uniform histologically, morphometry, histochemistry, immunohistochemistry, and microdissection with microchemical investigations have revealed marked heterogeneity on a functional and biochemical level. Hepatocytes from the periportal and perivenous zones of the liver parrenchyma differ in oxidative energy metabolism, glucose uptake and output, unreagenesis, biotransformation, bile acid secretion, and palsma protein synthesis and secretion. Although trace elements are intimately involved in the regulation and maintenance of these functions, little is known regarding the heterogeneity of trace element localization of the liver parenchyma. Histochemical techniques for trace elements generally give high spatial resolution, but lack specificity and stoichiometry. Microdissection has been of marginal usefulness for trace element analyses due to the very small size of the dissected parenchyma. The characteristics of the high-energy x-ray microscope provide an effective approach for elucidating the trace element content of these small biological structures or regions. 5 refs., 1 fig., 1 tab.

An X-Ray Microprobe Beam Line for Trace Element Analysis

The application of synchrotron radiation to a x-ray microprobe for trace element analysis is a complementary and natural extension of existing microprobe techniques using electrons, protons, and heavier ions as excitation sources for x-ray fluorescence. This was first recognized by HOROWITZ and HOWELL [1] in their development of the first synchrotron radiation microprobe at the Cambridge Electron Accelerator. SPARKS, et al. [2] used a miniprobe beam at the Stanford Synchrotron Radiation Laboratory in an attempt to find natural occurring superheavy elements by x-ray fluorescence of characteristic L-lines. The ability to focus charged particles leads to electron microprobes with spatial resolutions in the sub-micrometer range and down to 100 ppm detection limits and proton microprobes with micrometer resolution and ppm detection limits. The characteristics of synchrotron radiation that prove useful for microprobe analysis include a broad and continuous energy spectrum, a relatively small amount of radiation damage compared to that deposited by charged particles, a highly polarized source which reduces background scattered radiation in an appropriate counting geometry, and a small vertical divergence angle of ~ 0.2 mrad which allows for focussing of the light beam into a small spot with high flux. The features of a dedicated x-ray microprobe beam line developed at the National Synchrotron Light Source (NSLS) are described.