Dual detector micro-XRF cryotomography and mapping on the model organism Daphnia magna

The recent availability of a cryostream cooler at beamline L has allowed synchrotron radiation based micro-XRF analysis of frozen biological samples close to their native state. In a previous contribution, we compared the elemental distributions within a ydrated (frozen) and a fixed (dehydrated) Daphnia magna, which is a freshwater crustacean used in toxicological research as a model organism for evaluating effects of metals on the cosystem. Although hydrated samples show less dislocation of elements and/or sample contamination as compared to fixed samples, they are mainly composed of a water matrix, which is more susceptible to absorption effects of low energy X-rays. Therefore, we investigate the degree of absorption in 2D/CT micro-XRF elemental maps of Daphnia magna using a dual silicon drift detector (SDD) setup

In vivo XANES measuring technique for studying the arsenic uptake in cucumber plants

New in vivo X-ray absorption near edge structure measuring technique was developed by using liquid nitrogen steam flow for cooling cucumber samples keeping them under cryogenic conditions during the measurement in order to preserve the original chemical states of arsenic species in the hypocotyl. The aim of this study was to determine the As oxidation state in order to identify the possible metabolic processes during the nutrient uptake in cucumber (Cucumis sativus L. cv Joker) as model plant. The plants were grown in Hoagland's modified nutrient solution. The ratio of the quantity of two As species was determined in the hypocotyls of the cucumber samples: arsenite, As(III) and arsenate, As(V). The ultimate biological goal of the in vivo experiments was to investigate the applicability of the X-ray absorption near edge structure technique under cryogenic conditions and to specify the resistance level of the plants to arsenic toxicity when different chemical forms of iron, FeCl3 and Fe-ascorbate were supplied in the nutrient solution. We have examined the influence of the intense synchrotron radiation beam on the transformation of the oxidation number of both As species when the effect of the reactive oxygen forms was eliminated by the presence of ascorbate. Copyright (c) 2016 John Wiley & Sons, Ltd

Improved micro-X-ray fluorescence confocal imaging of two-dimensional distribution of arsenic concentration in cucumber hypocotyls using synchrotron radiation

An optimized micro-X-ray fluorescence confocal imaging (mu XRF-CI) analytical method has been developed to determine the 2D distribution of elemental composition in small (1-3 mm) biological objects at a 10-20 mu m spatial resolution. Plants take up chemical elements from soil, and the vascular system transports them toward shoots. In order to obtain biochemical information related to this biological process, 2D distributions of chemical elements in roots and in hypocotyls of cucumber plants were analyzed by synchrotron radiation based on micro-X-ray fluorescence computer tomography and mu XRF-CI techniques. The experiments were carried out at HASYLAB Beamline L of the DORIS-III storage ring in Hamburg, a facility that provided optimal physical conditions for developing and performing these unique analyses: high flux monochromatic synchrotron beam, X-ray optical elements, precision moving stages, and silicon drift detectors. New methodological improvements and experimental studies were carried out for applicability of lyophilized samples and cryo-cooling. Experimental parameters were optimized to maximize the excitation yield of arsenic K alpha radiation and improvement of the spatial resolution of the mu XRF-CI analytical method

Polycapillary-optics-based micro-XANES and micro-EXAFS at a third-generation bending-magnet beamline

A focusing system based on a polycapillary half-lens optic has been successfully tested for transmission and fluorescence mu-X-ray absorption spectroscopy at a third-generation bending-magnet beamline equipped with a non-fixed-exit Si(111) monochromator. The vertical positional variations of the X-ray beam owing to the use of a non-fixed-exit monochromator were shown to pose only a limited problem by using the polycapillary optic. The expected height variation for an EXAFS scan around the Fe K-edge is approximately 200 mm on the lens input side and this was reduced to similar to 1 mu m for the focused beam. Beam sizes (FWHM) of 12-16 mm, transmission efficiencies of 25-45% and intensity gain factors, compared with the non-focused beam, of about 2000 were obtained in the 7-14 keV energy range for an incoming beam of 0.5 x 2 mm (vertical x horizontal). As a practical application, an As K-edge mu-XANES study of cucumber root and hypocotyl was performed to determine the As oxidation state in the different plant parts and to identify a possible metabolic conversion by the plant

High resolution X-ray fluorescence micro-tomography on single sediment particles

This work focuses on the investigation of the distribution of contaminants in individual sediment particles from the New York/New Jersey Harbor. Knowledge of the spatial distribution of the contaminants within the particles is needed to enable (1) more sophisticated approaches to the understanding of the fate and transport of the contaminants in the environment and (2) more refined methods for cleaning the sediments. The size of the investigated particles ranges from 30-80 microns. Due to the low concentration of the elements of interest and the microscopic size of the environmental particles in these measurements, the small size and high intensity of the analyzing X-ray beam was critical. The high photon flux at the ESRF Microfocus beam fine (ID13) was used as the basis for fluorescence tomography to investigate whether the inorganic compounds are taken upon the surface organic coating or whether they are distributed through the volume of the grains being analyzed. The experiments were done using a 13 keV monochromatic beam of approximately 2 mum in size having an intensity of 10(10) ph/s, allowing absolute detection limits on the 0.04-1 fg level for Ti, Cr, Mn, Fe, Ni, and Zn