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Chemists need reliable methods to analyse and determine molecular structures. Nuclear magnetic resonance (NMR) and mass spectrometry are indispensable tools in daily chemical research for rapidly analysing molecular structures, but, [...], X-ray single-crystal diffraction (SCD) analysis has the intrinsic limitation that the target molecules must be obtained as single crystals. Here we report a protocol for SCD analysis that does not require the crystallization of the sample. In our method, tiny crystals of porous complexes are soaked in a solution of the target, such that the complexes can absorb the target molecules. Crystallographic analysis clearly determines the absorbed guest structures along with the host frameworks. Because the SCD analysis is carried out on only one tiny crystal of the complex, the required sample mass is of the nanogram-microgram order. We demonstrate that as little as about 80 nanograms of a sample is enough for the SCD analysis. In combination with high-performance liquid chromatography, our protocol allows the direct characterization of multiple fractions, establishing a prototypical means of liquid chromatography SCD analysis. Furthermore, we unambiguously determined the structure of a scarce marine natural product using only 5 micrograms of the compound.

Abstract: The review is concerned with the present-day correction models used in electron probe x-ray microanalysis (EPXMA). A general approach to constructing models of the excitation distribution function along the target depth is described. Specific correction methods are considered in detail. Article History: Registration Date: 07/10/2004

High-performance x-ray microcalorimeters were developed based on superconducting transition-edge sensors. The superconducting detectors, which are cooled by a compact adiabatic demagnetization refrigerator mounted on a scanning electron microscope provide significant new capabilities for x-ray microanalysis. The analysis of particles on Si wafers, including 0.3 micron tungsten particles and 0.1 micron alumina particles is described.

X-ray absorption near-edge structure (XANES) has been applied to the quantitative analysis of chromate (CrO42-) content in oxides, silicate glasses, and simulated cementitous waste forms. The method uses the normalized area of a pre-edge peak (bound-state transition) in XANES spectra acquired with the synchrotron X-ray microprobe on beam line X26A at the National Synchrotron Light Source. The estimated accuracy of the technique is + or - 5% in terms of Cr6+/total Cr. The minimum detection limit approaches 10 ppm Cr6+ using a 150-micrometer synchrotron X-ray beam. These results demonstrate the value of synchrotron-based microXANES for the nondestructive quantification of the first-row transition metal species present as tetrahedral oxyanions.

We present measurements of the x-ray focusing properties of square-pore microchannel plates (MCP's). Square-pore MCP's contain large numbers of closely packed optical surfaces, as required for grazing incidence x-ray optics. The surface of individual MCP channels has been measured and found to have high microroughness transverse to the channel axis and low microroughness parallel to the axis. The high frequency transverse roughness, on length scales greater than 400 nm, has a rms value of 5.9 nm and a Gaussian autocorrelation function with correlation length of 1.41 micrometer. We find that the geometric misalignments of the surfaces of different channels limit the angular resolution obtainable with current samples of MCP's to 7.1 arcmin.

In our previous studies, it has been demonstrated that both the excitation interactions between electrons and the atoms of the matrix and the matrix and geometric effects of electron-induced X-ray signals can be described by Monte Carlo simulation for low-Z elements, such as carbon, nitrogen, and oxygen, in individual atmospheric microparticles. In addition, by the application of a quantification method, which employs Monte Carlo simulation combined with successive approximations, at least semi-quantitative specification of the chemical compositions could be done. This has enlarged the scope of electron probe X-ray microanalysis (EPMA) for the single particle analysis of atmospheric environmental aerosol particles. In this work, we demonstrate that the heterogeneity of individual particles, even of micrometer size, can be characterized by the application of EPMA. X-ray photons obtained with different primary electron beam energies carry information on the chemical compositions for different regions in the particles. Artificially generated heterogeneous Ca[CO.sub.3]-Ca[SO.sub.4] individual particles were measured at different accelerating voltages, and it was found that the Monte Carlo calculation is a powerful technique to extract the information on the heterogeneity of the particles that is contained in the measured X-ray data. Our approach can even estimate the thickness of the surface CA[SO.sub.4] species by the application of the Monte Carlo calculation. A preliminary result for carbon-coated glass particles is also presented. The complexity involved in the analysis of real world particles is briefly mentioned with a result for heterogeneous Si[O.sub.2] particle.