[en] The emission spectra and fluorescence decay curves of solid UO₂²⁺-Datura at liquid nitrogen temperature have been measured. The linewidth of the emission packs of UO₂²⁺ ions in UO₂²⁺-Datura decreases with the UO₂²⁺ concentration. This linewidth broadening phenomenon can be explained by the existence of resonance interactions between adjacent UO₂²⁺-Datura species. The analysis of the emission peak position of the bound ions has been used to provide a measure of the electronic factors contributing to the interaction between the uranyl ion and phosphoryl and dicarboxyl moieties on the cell wall material. An observed blue shift of the uranyl fluorescence spectrum as a function of solution pH has been ascribed to a distortion of the normally linear O-U-O bond. An inter- and intra-molecular nonradiative energy transfer model has been successfully used to interpret the measured lifetime data of UO₂²⁺-Datura. 23 refs., 6 figs., 2 tabs

[en] Numerous studies have been directed toward elucidating the mechanisms by which analyte is excited in an inductively coupled plasma (ICP). However, excitation is only the final stage of a series of process which the analyte undergoes prior to the emission of a characteristic photon. These processes include droplet desolvation, sample vaporization, atomization, and ionization. Additionally, analyte ions or atoms can combine within the plasma to form molecular species, the band emission of which can interfere with the analytical signal. Atomization and molecule formation have been investigated here by means of an rf power amplitude-modulated ICP. Measurement of the temporal response of various species in the plasma to this modulation and the effect of modulation on the spatial distribution of species aids in assigning energy-transport, atomization, and recombination mechanisms. In order to remove the complications of aerosol droplet desolvation and solute particle vaporization from these studies, gaseous samples of the same analyte (carbon) in different forms (CO/sub 2/ and CH/sub 4/) have been introduced into the plasma. The use of carbon as a vehicle for study avoids also complications from ionization, because of the relatively high ionization energy of carbon (11.26 eV). Thus, observed temporal and spatial behavior of the atomic emission of carbon and the molecular band emission of C/sub 2/ radicals are indicative of the mechanism of atomization and molecular recombination, respectively

[en] The objective of this research was to characterize biologically produced materials for the recovery of toxic heavy metals from contaminated groundwaters. Specifically, components of the cells of the organism Datura innoxia (angel's trumpet) were investigated. Several approaches to understanding the interactions involved in the binding process have been employed. These methods range from the phenomenological to the fundamental. Measurement of the binding capacity of cadmium ions onto both the free Datura innoxia cells and immobilized cells has been undertaken. Immobilization of the cell material was observed to result in a significant increase in the amount of cadmium ion bound to the material. A methodology which will provide both the binding coefficient and the binding capacity of the metal ion has been developed. This is based on adsorption isotherms. A methodology for the rapid characterization of the binding of a metal pollutant with minimal generation of waste has been investigated. This methodology utilizes peak-shape analysis of transient signals resulting from the introduction of a small volume (<0.50 mL) of the metal-containing solution. Using europium as a probe species, it has been fluorometrically determined that at least two separate types of active binding sites exist on the cell walls of Datura innoxia. Specifically, these binding sites have been determined to be sulfate functionalities (pH≤3) and single and dual carboxylate containing sites (pH≤4). (author) 4 figs., 1 tab., 4 refs

[en] The spectrally and temporally resolved UO²⁺₂ fluorescence signals have been measured for solid samples of UO²⁺₂-Datura, UO²⁺₂-(immobilized Datura), and UO²⁺₂-(silicate polymer) at liquid nitrogen temperature. The binding capacity of UO²⁺₂ to Datura innoxia cell material has been enhanced significantly at pH 5 and 6 when immobilized in a polysilicate matrix. New binding sites having a greater binding strength with a lower availability have been observed for the binding of UO²⁺₂ after immobilization of the cultured biomaterial. However, chemical alteration of the cell material resulting from this immobilization process has not been observed. The chemical environment of the binding sites responsible for the binding of UO²⁺₂ in immobilized and free D. innoxia cell material has been demonstrated to be different. This difference results from the immobilization of the cell material within a polysilicate matrix. 19 refs., 8 figs., 4 tabs

[en] Diagnostic studies of the inductively coupled plasma (ICP) are essential to the understanding of atomization, ionization, and excitation in this emission source. In such studies, it is often desirable to spatially resolve the processes under investigation. In the past, spatially resolved diagnostic studies of the ICP have relied almost exclusively upon the Abel transformation (or ''inversion'') to construct radial profiles from lateral projection data. Unfortunately, the Abel transformation is known to suffer from several significant limitations. Small amounts of noise in the lateral projection data can adversely affect the accuracy of the reconstructed radial profiles and necessitate the use of elaborate smoothing and filtering techniques before the data are Abel inverted. Additionally, Abel transformation requires the assumption that the source has cylindrical symmetry. Small source asymmetries can result in distortion of the calculated radial profiles and make the subsequent interpretation of data difficult or impossible. To avoid the problems associated with the application of the Abel transform, other methods of mapping the ICP discharge should be considered. Computerized tomography (CT) offers one method for accurately reconstructing representations of asymmetric signals. Until quite recently, the computational complexity of CT discouraged its use in plasma-diagnostic studies. Now, with the ready availability of inexpensive computer power, CT becomes a viable alternative to Abel inversion for many ICP studies

[en] The inductively-coupled plasma (ICP) has been demonstrated to be an efficient source of atoms and ions. This high temperature environment of atoms results in complex emission spectra which are typically observed by optical emission techniques. The spectral interferences resulting from these complex emission spectra may be eliminated or minimized by utilizing an alternate optical interaction for the detection of species within the ICP. The use of the atomic magneto-optical rotation effect (AMORE) provides a method for such a simplification of the analytically useful spectrum. The instrument for AMORE detection of analyte utilizing an ICP is being designed and constructed within the authors laboratory. Earlier designs of the system resulted in undesirably high background emission levels. Several approaches to the minimization of analyte and plasma background emission have been investigated. Among these approaches have been the use of high fidelity optical spatial filtering, the use of phase sensitive detection electronics, and modulation of the amplitude of the applied rf field with time- gated detection. The respective merits of each of these approaches is discussed and the experimental configuration of each is described

[en] Spatially resolved diagnostic studies of the Inductively Coupled Plasma (ICP) have generally relied upon the Abel inversion process to transform lateral projection data into radially resolved emission or absorption profiles. Unfortunately, Abel transformation is known to possess several significant drawbacks. The validity of the radial profiles obtained from the Abel-inversion process is significantly degraded by even small amounts of noise in the lateral emission data. In addition, the Abel-inversion technique requires a cylindrically symmetrical object in order to faithfully produce reconstructions. One method of avoiding these problems is to use the more general method of tomographic reconstruction for spatially resolved studies in the ICP. The experimental requirements of tomographic reconstruction, however, necessitate a rather elaborate experimental system. The large number of angular projections, resolution elements per projection, and the sheer volume of data collected makes tomographic reconstruction prohibitively time consuming if an automated, multi-channel collection scheme is not employed. In this study, an experimental system was designed to permit tomographic characterization of a laboratory ICP. The system employs a z-theta translation stage, a silicon intensified target vidicon detector and a laboratory computer for system automation (see figure). A typical data collection scheme is to obtain 60 projections with 100-point resolution per projection. These profiles are collected every 2 mm on the vertical axis, requiring 15 profiles over a 30 mm plasma height. This process results in approximately 90,000 data points, which can be collected within an hour on this system. Tomographic reconstruction is achieved with the use of a VAX-780 computer. The system employed is described and the operating characteristics of the apparatus are discussed

[en] The selective removal of metal pollutants from water systems is necessary for their treatment. Several different media have been identified as potential adsorbants. Among these is the bio-mass material from Datura Innoxia (Jimson weed). The cell walls of these single-cell organisms has been immobilized and characterized in terms of elucidating the mechanisms of metal binding. Procedures for the determination of such fundamental parameters for equilibrium measurements will be described in this paper. These procedures include the analysis of adsorption isotherms, high-field nuclear magnetic resonance spectrometry, and solid-state fluorescence spectroscopy. The application of those procedures to the binding of Cd, Zn and Eu to immobilized Datura will be discussed

[en] The excitation spectra associated with the ⁷F₀→⁵D₀ transition of Eu⁺³ has been used to examine the binding sites on cell wall fragments of Datura innoxia. Both native and esterified cell wall fragments were each examined at pH 5 and pH 2 to determine the contributions to metal ion sorption from both the carboxylate and sulfonate functional groups. The excitation spectra have been deconvoluted into the individual groups responsible for metal ion uptake. At least four unique binding sites can be described as being responsible for metal ion uptake. The higher affinity sites involve carboxylates in the binding of Eu⁺³ in a tridentate (3:1 ligand-to-metal ratio) configuration. copyright 1997 Society for Applied Spectroscopy