Search Results

You are looking at 1 - 10 of 28 items for :

  • Author or Editor: D. Anderson x
  • Chemistry and Chemical Engineering x
  • All content x
Clear All Modify Search

Abstract  

Thermal neutron capture prompt gamma-ray activation analysis (PGAA) was used to determine mass fractions of H, B, C, N, Na, Cl, K, and S in 2 meat homogenates. Twelve units of candidate Standard Reference Material (SRM) 1546 Meat Homogenate produced by the National Institute of Standards and Technology (NIST) were analyzed to provide NIST with certification data. This SRM is a realistic processed food matrix, ideal for food analysis programs such as the Food and Drug Administration's Total Diet Study. Another meat homogenate, Certified Reference Material LGC 7002 Pork/Chicken (along with NIST SRMs 1549 Non-Fat Milk Powder and 1571 Orchard Leaves) was analyzed for quality control. Candidate SRM 1546 unit-to-unit heterogeneity was <2% for H, Na, Cl, and K, and 3.5% for N and within-unit heterogeneity was <2% for H, N, Cl, and K, and 2.9% for Na, similar to LGC 7002 homogeneity results. Control material mass fractions agreed well with certificate and consensus values. Protein mass fractions, calculated from N results, were 15.2% and 11.9% for candidate SRM 1546 and LGC 7002, respectively. Protein content calculated for SRM 1549 (36.0%) agreed well with known values for dried non-fat milk powder.

Restricted access

Abstract  

Twenty-one ready-to-use hobby glazes, of which 18 were labeled safe for food containers (SFFC), were analyzed for Al, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, Gd, Hf, K, Mn, Na, Pb, Si, Sm, Sr, Ti, Zn, and Zr by neutron capture prompt -ray activation analysis (PGAA). Simultaneously, Pb was also determined by X-ray fluorescence spectrometry (XRFS) using Pb K X-rays induced by the -ray component of the neutron beam. The XRFS limits of detection were 200–400 g Pb·g–1 (dry weight), a factor of 100 better than those for PGAA. Pb concentrations (by dry weight; with weight losses ranging from 28 to 49% after air-drying) found were 0.16–27.2% in the SFFC glazes and 0.86–32% in the other glazes. The SFFC glazes contained from <0.6 to 202 g Cd·g–1, and Co, Cr, and Cu (elements which may enhance Pb leaching from fired glazes) were found in concentrations up to 1.2, 2.7, and 5.6%, respectively. Method accuracy was demonstrated with the analysis of soil, fly ash, and glass standard reference materials.

Restricted access

Abstract  

Compton suppression spectrometry was used to analyze foods for elements with short-lived neutron activation products (half-lives of about 2 minutes to 1.5 days). Analysis conditions were optimized to provide quality assurance analyses for iodine in FDA’s Total Diet Study. Iodine mass fractions (0.075 to 2.03 mg/kg) were measured in 19 of 42 foods analyzed, with limits of detection (LODs) ranging from 0.03 to 1.4 mg/kg, mostly depending on NaCl content. LODs were lowered by up to a factor of 2 for 16 elements. Suppression factors ranged from about 2 to 8 over the energy range 400 to 3200 keV.

Restricted access

Abstract  

Background enhancements in neutron capture prompt -ray activation analysis were determined over a large range of total scattering cross sections by irradiating graphite, S, Be, paraffin, urea and H2O targets. Relative to irradiations using no target, B, Na, Cl, Al, and Pb backgrounds were 7–12 times greater with 2 ml of H2O, but N and Fe backgrounds were only 1.2 and 1.75 times greater, respectively. For biological targets, background count rates can be determined as functions of the 2223 ke V H photopeak count rate.

Restricted access

Abstract  

Fifteen maple syrups were analyzed for137Cs and K (via40K) by using a low-background -ray counting system, and for B and K by using neutron capture prompt -ray activation analysis (PGAA). For low-background -ray counting, 3 limits of detection (24-hour counts) were 0.03 Bq137Cs/kg and 10 mg K/kg for 3.5-L portions and 0.08 Bq137Cs/kg and 20 mg K/kg for 1.0-L portions. K concentrations determined by the two methods (using 2-g portions for PGAA) were in excellent agreement. The products were obtained in 1991, with one produced in Maryland, three in New York, four in Pennsylvania, two in New Hampshire, and five in Canada. The average activity concentration for Canadian syrups (2.8 Bq137Cs/kg) was nearly a factor of 20 greater than the average (0.15 Bq137Cs/kg) for the other syrups, but all137Cs activity concentrations were at least 100 times lower than those for which controls would be recommended according to Federal Radiation Council guidance. The data exhibited distinct groupings related to the sources of the products when the ratios of137Cs activity to K content (BqCs/mgK) were plotted vs. B concentrations.

Restricted access

Abstract  

This review focuses on dissolution/reaction systems capable of treating uranium metal waste to remove its pyrophoric properties. The primary emphasis is the review of literature describing analytical and production-scale dissolution methods applied to either uranium metal or uranium alloys. A brief summary of uranium's corrosion behavior is included since the corrosion resistance of metals and alloys affects their dissolution behavior. Based on this review, dissolution systems were recommended for subsequent screening studies designed to identify the best system to treat depleted uranium metal wastes at Lawrence Livermore National Laboratory (LLNL).

Restricted access

Abstract  

Screening experiments were performed to evaluate reagent systems that deactivate pyrophoric, metallic depleted uranium waste streams at ambient temperature. The results presented led to the selection of two systems, which would be investigated further, for the design of the LLNL onsite treatment process of metallic depleted uranium wastes. The two feasible systems are: (a) 7.5 mol/l H2

Restricted access
Form indexes for DTA or TG curves (S T orS x) must be treated separately. Only forS x can clear relations to be developed for the order of reactionn. In the rational range ofn between 0.5 and 3.0 we found for linear, exponential and hyperbolic programmes these functions were found to be of the type
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$S_x = an^{0,5} + b$$ \end{document}
Restricted access