Comparison of portable detectors for uranium enrichment measurements

Uranium enrichment and holdup measurements require a detector capable of accurately obtaining the 186-keV peak area. NaI detectors have been widely used for these tasks. However, for recycled uranium, the interference of the 239-keV peak from the ²³²U decay chain challenges the capabilities of the NaI detectors to accurately extract the area of the 186-keV peak. Using CZT detectors, which have much better resolution than the NaI detectors, has temporarily solved this interference problem. However, the CZT detectors have setbacks in that they are generally small and have low efficiencies, which require long acquisition times for reasonable statistics. Recently, two new types of scintillator detectors have become available commercially, LaCl₃(Ce) and LaBr₃(Ce). These cerium-doped lanthanum halide detectors, with comparable resolution but better efficiency than the CZT detectors, appear to permanently solve the interference problem for recycled uranium measurements. In this report, we compare the uranium enrichment measurement performances of a portable NaI detector, a large coplanar-grid CZT detector, and a LaBr₃ detector.     

Comparing Electrochemical,Fluorescence, and Ultraviolet Detectors for HPLC Analysis of the Decapeptide,Nafarelin

Abstract

This report describes a reverse-phase HPLC technique to determine the concentration of nafarelin (a decapeptide luteinizing hormone-releasing hormone analog) in aqueous solutions for intranasal administration. Pursuant to the method development we evaluated three different detectors with respect to sensitivity, linearity, specificity and reliability. The three detector types investigated were: spectrophotometric (225 nm), electrochemical (at +1.2 v), and fluorescence (excitation = 282 nm, emission = 332 nm). All three detectors gave satisfactorily linear response, and gave equivalent results for nafarelin samples assayed in parallel. The lower detection limits for the three detectors were: ultraviolet = 1.5 ng, electrochemical = 2.0 ng, and fluorescence = 0.6 ng. Thus, the three detector types are nearly equally sensitive for nafarelin analysis. For routine determinations the ultraviolet detector is superior to the electrochemical and fluorescence detectors with respect to convenience of operation.     

High Performance Liquid Chromatographic Determination of Phenylenediamines in Aqueous Environmental Samples

Abstract

The use of high performance liquid chromatography (HPLC) for the determination of phenylenediamines has been studied. Detection limits using both ultraviolet (UV) and electrochemical (EC) detectors have been determined and EC is superior in most cases. Chromatographic conditions and sample preparation procedures are described for many phenylenediamines of environmental significance.     

Separation and Characterization of the Prostaglandins by Gas Chromatography and Mass Spectrometry

Abstract

Prostaglandins of the A, B, E and F series, together with 8-iso-E₁, have been separated and characterized by gas chromatography and mass spectrometry through the use of TMSi and MO-TMSi derivatives.

These derivatives are suitable for work with GLC systems with flame ionization detectors. Additional derivatives must be sought for detection by electron capture techniques.     

Electronic Tongue Applied to Phenolic Compounds Analysis

Abstract

A new voltammetric electronic tongue has been developed for the simultaneous determination of p-aminophenol, p-chlorophenol, and p-chloro-m-methylphenol. The three analytes are high environmental pollutants. Three epoxy-graphite composite electrodes have been used as detectors, with two of them being modified by the addition of metal catalysts in their composition. Simple fixed potential voltammetry has been used in order to simplify measurements. Artificial neural networks were used as chemometric tools for learning and prediction of the system. Good correlations in both modeling and predicting capacities have been obtained for the range of 1 to 28 µM of the three phenolic compounds.     

Size Exclusion Chromatography (SEC) of Complex Polymers - Generalized Analytical Corrections for Imperfect Resolution

Abstract

Herein is reported generalized analytical solutions which permit correction for imperfect resolution when the molecular weight calibration curve is nonlinear and the variance of single-species chromatograms changes significantly with molecular size of the polymer solute. Two kinds of generalized analytical solutions have been obtained. One is a solution of Tung's integral equation for the corrected chromatogram or the molecular weight distribution and the other is a solution for the corrected molecular weight averages of the whole polymer. Also discussed is the use of local corrections for imperfect resolution across the chromatogram with detectors such as the low angle laser light scattering spectrophotometer (LALLS) when used with micro and macropackings.     

Polyphosphonium Salts as Templates for New Zeolites

Abstract

Zelites have conventionally been prepared using quaternary ammonium salts as templates which control the pore size nnd structure of the resulting material. A range of polyammonium and -phoaphonium salts of the types shown have been prepared for evaluation in directing the formation of new zeolite structiires, particularly those with large pore sizes which may be useful a, ciitalysts for organic reactions.¹ As shown by the examples below, the construction of one, two and three dimensional ternplates is in progress.     

Problems in Determining Compositional Heterogeneity of Copolymers by Size-Exclusion Chromatography and UV-RI Detection System

Abstract

The compositional heterogeneity of styrene-methylmethacrylate copolymer has been evaluated by a UV-RI dual-detector method and by a RI detector-pyrolysis-gas chromatographic method and problems associated with the determination of the chemical heterogeneity by a UV-RI method are discussed. The quotient of signals H(UV)/H(RI) of both the detectors (UV and RI) for polystyrene increased at the extreme parts of the molecular weight distribution owing to nonlinearity of UV response. The correction of the quotient of signals of both detectors for the copolymer was proposed. The UV and RI response factors for the copolymer were supposed to differ from those for homopolymers. Reproducibility for the detector responses influences the values of chemical heterogeneity much more than expected. To overcome these problems, the detection method to obtain each composition independently using different detectors will be preferable.     

Development of Calcium Phosphate Glass-Ceramics for Surgical and Dental Use

Abstract

Two types of glass-ceramics have been developed in the system of calcium phosphate without silica. The preparation conditions, crystallization processes, and some of physical properties are briefly reported. These glass-ceramics have high potential use for bone substitutes and dental materials such as dental crown, root and tooth.     

Corrections for Instrumental and Secondary Broadening in the Chromatographic Analysis of Linear Copolymers

Abstract

The effects of instrumental broadening and of polymer/solvent/packing interactions (secondary broadening) are separately investigated in the context of chromatography experiments, for the characterization of linear copolymers with two types of repeating units. The problems associated to the estimation of: a) the joint molecular weight distribution - chemical composition distribution (MWD-CCD) through orthogonal chromatography; and of b) the average MWD - average CCD through standard size exclusion chromatography (SEC) with dual detection are considered. The main difficulty with the secondary broadening correction, is the calibration for this effect. In the case of standard SEC with dual detection, a simple solution was found to the instrumental broadening problem, that involves a direct extension of the calibration and deconvolution techniques developed for linear homopolymers and mass detectors.     

C-Phosphorylation of Electron-Rich Heterocycles

Abstract

C-phosphorylation of pyrrole, furan, thiophene derivatives and their benzanalogs by phosphorus tribromide has been studied. Perspective methods for involving trivalent phosphorus residues at a different position of the rings have been developed. Unknown early the heterocycle's derivatives with tri- and tetracoordinated phosphorus substituents (1–5) and novel types of phosphoruscontaining heterocycles (6,7) have been obtained.     

A Simple Solvent Programmer for Liquid Chromatography. I

Abstract

Equations have been derived from which the dimensions of a solvent gradient generator, coupled to open tubular, micro-packed, semi-micro packed or conventional HPLC columns, may be calculated for a desired gradient volume. Packed and open-tubular generators have been considered. Calculations, using the derived equations, predict that a generator of particular dimensions is needed for each column type. These dimensions are practically feasible for all column types except the conventional column.     

New Structures from Multiple Rearrangements of Propargylic Dialkoxy Disulfides

Abstract

Sundry dipropargyloxy disulfides have been successfully prepared and their rearrangement paths and products have been found to be dependent upon their substitution pattern. Inter alia compounds of two heretofore unknown structure types— 10 and 11 on the one hand and 14 and 15 on the other—have been obtained and characterized.     

An Analysis of Imperfect Resolution in the Chromatography of Particle Suspensions

Abstract

Here-in is reported a general method of correction for imperfect resolution in the chromatography of particle suspensions. It overcomes most of the limitations of previously reported methods. A non-linear particle diameter - retention volume calibration curve and a generalised spreading function are considered. Moment equations are developed for two types of general detectors; the first type includes a refractive index detector and a turbidity detector with Rayleigh scattering while the second type includes a tubidity detector with Mie scattering. The moment equations were applied to the analysis of chromatograms of narrow Dow polystyrene latices measured by size exclusion chromatography.     

Enhancement of the Fluorimetric Properties of Some Carboxyl Substituted Anthracenes by Complexation with Bovine Serum Albumin

Abstract

A study has been conducted of the fluorimetric properties of substituted anthracenes, following complexation with bovine serum albuinin(BSA). It was found that although protein binding of the ligands enhances their fluorimetric properties, it fails to do so for their phosphorimetric properties. BSA would serve well in post column reactors for HPLC detectors, but not in pre-column systems.     

Viscosity Detection with a Pulseless PUMP for Liquid Chromatography

Abstract

The performance of a differential pressure transducer as a viscosity detector in conjunction with a pulseless high pressure syringe pump designed for the purpose is described. The detector, although relatively insensitive, is inexpensive and extremely rugged. Because it is non-destructive and introduces very little dispersion, serial coupling ahead of other detectors is possible. Response behavior is demonstrated.     

Investigation of Instrument Parameters for the Application of Peroxyoxalate Cheminescence Detection to Microbore Chromatography

Abstract

Peroxyoxalate chemiluminescence generated by the reaction of an oxalate and hydrogen peroxide in the presence of a fluorophor was evaluated as a detection system for microbore liquid chromatography. The results of studies on instrumental parameters show that the signal is increased with short reaction lines, increasing flow cell volume, and enhanced response through detectors with improved optics.     

2-(Diphenylacetyl)-1,3-Indanedione-1-Hydrazone (Dipain) Derivatives for Detection of Trichothecene Mycotoxins

Abstract

2-(Diphenylacetyl)-1,3-indanedione-1-hydrazone and its derivatives where the NH₂ has been replaced by a substituted NH or an imino group give fluoresence enhancement with trichothecene mycotoxins. Absolute amounts of T-2 toxin as low as 50 ng are detectable. Detection limits for HT-2, Diacetoxyscirpenol, Neosolaniol, and Fusarenon-X range from 0.1 to 4μg.

The advantage in using 2-(diphenylacetyl)-1,3-indanedione-1-hydrazone (DIPAIN) derivatives for the detection of trichothecene mycotoxins is that response time is based on the rate of formation of a molecular association complex between the toxin and the detector reagent rather than on the chemical reactivity of the toxin. Hence, sensitive detection or mycotoxins can be achieved simply and rapidly at 25°C.

Since DlPAlN derivatives have been found to be direct-acting reagents capable of detecting droplets of dissolved trichothecenes, it is speculated that they may be useful as coatings in optical waveguide devices or in other devices that are developed as field detectors for aerosols that contain trichothecene mycotoxins. The DlPAlN reagents may also be used in kits that are designed to detect surface contamination by trichothecene mycotoxins.     

Calibration of Separation and Instrumental Peak Broadening in Sec Coupled with Light Scattering of Simple Polymers

Abstract

A recently developed procedure for calibration of separation and instrumental peak broadening in SEC was used for a comparative study of separation and axial dispersion of polystyrene, poly(methyl methacrylate) and poly(vinylchloride). The influence of the uncertainty in the volume lag between the concentration and LALLS detectors upon peak broadening was investigated and a new procedure for the determination of the lag was proposed. The applicability of the universal calibration concept was tested; all the polymers have been found to match a single universal calibration function. Polystyrene and poly(methyl methacrylate) also coincided very well with respect to the instrumental spreading, but for poly(vinylchloride) spreading was found to be a function of polymer concentration.