Image atomic emission using

Analytical Considerations with Image Devices. In considering the role of image devices in SMA, one should not lose sight of the analytical constraints involved. For example, typical analytical samples contain elements present at major-, minor-, and trace levels. In most cases it will not be possible to dilute the sample extensively and still determine the trace elements. As a result, the analytical lines employed in the determination should be selected with the expected concentrations of the elements in mind. Thus less sensitive analytical lines (such as nonresonance lines if the sample is analyzed by atomic emission) should be chosen for the determination of major- or minor elements, whereas the most sensitive resonance lines will need to be used for the determination of trace elements. Even though the same set of... 

Complete MCP s can be stacked to provide even higher gains. For response in the vacuum ultra-violet spectral region (50-200 nm) a SSANACON, self-scanned anode array with microchannel plate electron multiplier, has been used (36). This involves photoelectron multiplication through two MOP S, collection of the electrons directly on aluminum anodes and readout with standard diode array circuitry. In cases where analyte concentrations are well above conventional detection limits, multi-element analysis with multi-channel detectors by atomic emission has been demonstrated to be quite feasible (37). Spectral source profiling has also been done with photodiode arrays (27.29.31). In molecular spectrometry, imaging type detectors have been used in spectrophotometry, spectrofluometry and chemiluminescence (23.24.26.33). These detectors are often employed to monitor the output from an HPLC or GC (13.38.39.40). 

The X-ray diffraction (XRD) patterns were obtained by Philips X pert Pro X-ray diffractometer equipped with a Cu-K source at 40 kV and 40 mA. The crystalline sizes of R particles were calculated from Scherrer s equation [15]. Transmission electron microscopy (TEM) images were obtained using the G2 FE-TEM Tecnai microscope at an accelerating voltage of 200 kV. The content of platinum and carbon in the sample was determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES, RF source Jobin Yvon 2301, 40.68 MHz). 

Charge coupled detectors These devices are not yet commonly available in commercial instrumentation for analytical spectrophotometry although they are used in applications in inductively coupled plasma atomic emission spectrometry. However, they have found extensive application in imaging and astronomical applications. Essentially they are two-dimensional photodiode arrays which allow many spectra to be acquired in one readout. A typical array sensor is shown in Figure 9. 

The field emission microscope and the field ion microscope are used primarily in the study of surface phenomena. With the field emission microscope, one can determine how the electron work function varies with crystallographic orientation, and how it is affected by the absorption of foreign materials. Magnifications of better than a million make it possible to observe effects on an atomic scale. Individual atoms and adsorbed molecules can be located with the field ion microscope. Very recently Muller " has adapted a mass spectrometer to the field ion microscope so that, in principle, single atoms may be imaged, evaporated, and analyzed. Unfortunately, the field methods are severely limited with respect to the materials that can be studied. Only highly conducting metals can be used, and then they must be thinned to a very sharp point. Some work has been done on molecules adsorbed on the points but this is also very limited. 

Positron emission tomography (PET) makes use of a short-lived positron emitter such as fluorine-18 to image human tissue with a degree of detail not possible with x-rays. It has been used extensively to study brain function (see illustration) and in medical diagnosis. For example, when the hormone estrogen is labelled with fluorine-18 and injected into a cancer patient, the fluorine-bearing compound is preferentially absorbed by the tumor. The positrons given off by the fluorine atoms are quickly annihilated when they meet... 

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