Fluorescence analysis, solid solutions

We prepared thin film Pt alloy electrodes by Ar-sputtering Pt and the second metal targets simultaneously onto a disk substrate at room temperature (thickness approximately 200 nm). The resulting alloy composition was determined by gravimetry and X-ray fluorescent analysis (EDX). Grazing incidence (i7= 1°) X-ray diffraction patterns of these alloys indicated the formation of a solid solution with a face-centered cubic (fee) crystal stmeture. 

A similar simplifying assumption has been used by Allain et al.(90) in analyzing their experiments on a flexible fluorescent anthracene-polystyrene copolymer coil in the vicinity of a nonadsorbing wall. The analysis appears to confirm a local decrease in C(z) for small z at the solid/solution interface. Such a depletion layer is interpreted in terms of an entropic repulsion ... 

Melting of samples is necessary for performing the analysis of ceramics and glass materials by means of x-ray fluorescence (XRF). Lithium tetraborate is added as flux for lowering the melting temperature. The homogeneous disks that form can be considered a solid solution of the sample compounds in the binder. 

Azulene has weak absorption in the visible region (near 7000 A) and more intense band systems in the ultraviolet. The first ultraviolet system, which commences at about 3500 A, has been examined in substitutional solid solution in naphthalene (Sidman and McClure, 1956) and in the vapour state (Hunt and Ross, 1962), and can be observed in fluorescence from the vapour (Hunt and Ross, 1956). Theory predicts that the transition is 1Al<-lAl(C2K), i.e. allowed by the electronic selection rules with polarization parallel to the twofold symmetry axis (see, e.g., Ham, 1960 Mofifitt, 1954 Pariser, 1956b). The vibrational analysis shows that the transition is allowed but does not establish the axis of polarization. The intensity distribution among the vibrational bands indicates a small increase in CC bond distance without change in symmetry. 

In the preceding chapter it had already been discussed that it is less the synthesis itself which may be the bottleneck in high-throughput zeolite science but rather the analysis of the solids formed in a high-throughput program. There are several standard characterization techniques which are typically employed to characterize zeolitic materials. These include powder XRD for phase identification, X-ray fluorescence analysis (XRF) or atomic absorption spectrometry to analyze elemental composition, sorption analysis to study the pore system, IR-speclroscopy, typically using adsorbed probe molecules to characterize the acid sites, NMR spectroscopy and many others. For some of these techniques parallelized solutions have been developed and described in the literature, other properties are more difficult to assess in a parallelized or even a fast sequential fashion. 

X-ray fluorescence spectroscopy (XRF) has been used for many years for the measurement of major and minor elemental concentrations. Improvements made in the sensitivity in recent years now allow the technique to be applied to the analysis of trace elements. A problem is that the sensitivity of XRF decreases dramatically for lower atomic number elements so the technique cannot be used for quantification of elements with atomic numbCT Z < 9. When compared to XRF, modern AA or AE instruments are simpla- to use, less expensive, have similar precision of analysis and have bettCT sensitivity. Optical atomic spectroscopy is ideally suited to the analysis of solutions so the method requires complete dissolution of the powder in a liquid. In comparison, XRE is ideally suited to the analysis of solid samples, and this can be a distinct advantage for cCTamic powders that are commonly difficult to dissolve. Table 3.7 includes a summary of the main features of optical atomic spectroscopy and XRF. 

Fluorescence Analysis of Organic Molecules in Solid Solutions. 748... 

In Section 2.0 we examine trapping experiments in the aryl vinyl polymers, for which the trap is an excimer forming site (EFS). A one dimensional random walk model is used for analysis of the transient and photostationary fluorescence in dilute solution. In a second study, the three-dimensional results of LAF [5] are applied to trapping experiments in pure solid films of aryl vinyl polymers. 

Tarascon et al. (1980) investigated the valence transition of Sm in the hexaboride solid solutions Sm, M B (M = Yb, Sr +, La ", Y, Th +). Samples were prepared by borothermal reduction of the mixed oxides under vacuum and high temperatures. The exact values of x have been determined by x-ray fluorescence analysis and checked by density measurements. Density measurements. X-ray and chemical analysis of SmB indicate an atomic ratio B/Sm x 6. From X-ray absorption measurements at the L, edge at 300 K the Sm + Sm + atomic ratio was obtained as a function of x. (The L,n absorption spectrum of Eu + in EuB was used as reference.) Y + substitution of Sm decreases the average Sm valence towards Sm in accordance with estimations of the average Sm valence in the hexaborides (Sm, Sm +), M B from lattice parameter measurements, fig. 34c. Lattice parameters of Sm +B a = 4.186, and Sm + Bg a = 4.115, were derived from interpolations of neighboring divalent and trivalent rare earth hexaborides. 

A preliminary test for the biodegradability of the 3-phenyl- and 3-carbamoyl-2(lH)pyridones was conducted in a barnyard humus suspension. The analysis by HPLC showed some loss, and the fluorescent compounds seemed to be adsorbed onto the solid. The 3-carbamoyl-2(lH)pyridone (II) also hydrolyzed to 3-carboxylic acid-2(lH)pyridone both in the slurry test and in water solutions that had been left standing 1-2 weeks. In preliminary tests both the 3-phenyl- and the 3-carbamoyl-2(lH)pyridones apparently adsorbed to some extent on silica sand columns. In addition, the solubility of both 1-H compounds was somewhat low, 1.3 x 10 M for II, and 1.0 x 10 M for IV. 

Figure 16.6 The solid phase ICAT reagent provides a thiol-reactive iodoacetyl group to capture cysteine peptides, a spacer containing stable isotopic labels, and a photo-cleavable group that can release the captured peptides for mass spec analysis. The VICAT mass tag is a solution phase labeling agent that also has a photo-cleavable site to release isolated peptides from a (strept)avidin affinity resin. This compound adds a fluorescent group to better detect labeled peptides as they are being isolated from a sample.

Cadmium in acidified aqueous solution may be analyzed at trace levels by various instrumental techniques such as flame and furnace atomic absorption, and ICP emission spectrophotometry. Cadmium in solid matrices is extracted into aqueous phase by digestion with nitric acid prior to analysis. A much lower detection level may be obtained by ICP-mass spectrometry. Other instrumental techniques to analyze this metal include neutron activation analysis and anodic stripping voltammetry. Cadmium also may be measured in aqueous matrices by colorimetry. Cadmium ions react with dithizone to form a pink-red color that can be extracted with chloroform. The absorbance of the solution is measured by a spectrophotometer and the concentration is determined from a standard calibration curve (APHA, AWWA and WEF. 1999. Standard Methods for the Examination of Water and Wastewater, 20th ed. Washington, DC American Public Health Association). The metal in the solid phase may be determined nondestructively by x-ray fluorescence or diffraction techniques. 

Certain compounds, whether present in solution or in solid state (as molecular or ionic crystals) emit light when they are excited by photons in the visible or near ultraviolet domain of the spectrum. This phenomenon, called luminescence, is the basis of fluorimetry, a very selective and sensitive analysis technique. The corresponding measurements are made with fluorimeters or spectrofluorimeters and, for chromatographic applications, with fluorescence detectors. 

In a method proposed by Booth et al. (141) for the determination of phylloquinone in various food types, extracted samples are subjected to silica solid-phase extraction followed, in the case of meat or milk samples, by further purification using reversed-phase solid-phase extraction or liquid-phase reduction extraction, respectively. The final test solution is analyzed by NARP-HPLC, and the fluorescent hydroquinone reduction products of phylloquinone and the internal standard are produced online using a postcolumn chemical reactor packed with zinc metal. 2, 3 -Dihydrophylloquinone, a synthetic analog of phylloquinone, is a suitable internal standard for the analysis of vegetable juice, whole milk, and spinach. Another synthetic analog, Ku23), is used for the analysis of bread and beef, because a contaminant in the test solution coelutes with dihydro-phylloquinone. 

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