Search Results

You are looking at 21 - 25 of 25 items for

  • Author or Editor: R. Filby x
  • Refine by Access: All Content x
Clear All Modify Search

Abstract  

A method for the preconcentration of Am and Pu from human tissue solutions (liver, lung, bone etc) using the Actinide-CU Resin (ElChroM Industries) has been developed for their alpha-spectrometric determination. With near 100% recoveries were obtained by preconcentration, subsequent decomposition methods for eluent were developed. Good agreement for Pu and Am determination with the USTUR anion-exchange/solvent extraction method was demonstrated using previously analyzed human tissue solutions and NIST SRMs. The advantages of the preconcentration method applied to human tissue analysis are simplicity of operation, shorter analysis time compared to anion exchange/solvent extraction methods, and capacity to analyze large tissue samples (up to 15 g bone ash per analysis and 500 g soft tissue).

Restricted access

Abstract  

The determination of isotopic thorium by alpha spectrometric methods is a routine practice for bioassay and environmental measurement programs. Alpha-spectrometry has excellent detection limits (by mass) for all isotopes of thorium except 232Th due to its extremely long half-life. This paper discusses improvements in the detection limit and sensitivity over previously reported methods of pre-concentration neutron activation analysis (PCNAA) for the recovery corrected, isotopic determination of thorium in various matrices. Following irradiation, the samples weredissolved, 231Pa added as a tracer, and Pa isolated by two different methods and compared (extraction chromatography and anion exchange chromatography) followed by alpha spectrometry for recovery correction. Ion exchange chromatography was found to be superior for this application at this time, principally for reliability. The detection limit for 232Th of 3.5 · 10-7 Bq is almost three orders of magnitude lower than foralpha spectrometry using the PCRNAA method and one order of magnitude below previously reported PCNAA methods.

Restricted access

Abstract  

Three proposed National Bureau of Standards clay standard reference materials, flint clay SRM 97b, plastic clay, SRM 98b, and brick, SRM 679 were investigated for homogeneity with respect to their contents of Sm, La, Sc, Th, Hf, As, Ga, Fe and Cr. Sub-samples were analyzed by instrumental neutron activation analysis (INAA) and replicate determinations were made on nominal sample weights of 100, 400, 750, and 1000 g. For Sm, La, Sc and Th, no increase in the relative standard deviation with decreasing sample weight was observed in all SRMs indicating that subsampling error for these elements was not a large component of the overall error. For Ga in all SRMs and Cr, As and Fe in SRM 98b, an increase in the relative standard deviation with decreasing sample weight suggests that these elements are concentrated in a minor component of the sample. The three clays should be good reference materials for trace element microanalysis for the elements investigated.

Restricted access

Abstract  

National Bureau of Standards residual fuel oil Standard Reference Materials, SRM 1619, 1620a, 1634a, and former SRM 1634 were analyzed for 20 trace elements by instrumental neutron activation analysis to determine whether these materials are suitable trace element standards for elements other than the 6 elements certified in SRM 1634a. The SRM 1634a is a suitable standard for Ni, V, Se, Na, Zn, As, Cr, Fe, Ce, Sm and La but Co, Ba, Nd, Cs, Eu, Sc, and Sb appear to be heterogeneously distributed and are probably present in mineral particulates. The SRM 1619 is a convenient standard for V and for low Ni content oils, but SRM 1620a does not appear to be a suitable standard for any trace element investigated.

Restricted access
Journal of Radioanalytical and Nuclear Chemistry
Authors:
A. Oluwole
,
O. Asubiojo
,
J. Nwachukwu
,
J. Ojo
,
O. Ogunsola
,
J. Adejumo
,
R. Filby
,
S. Fitzgerald
, and
C. Grimm

Abstract  

A total of 40 crude oils from 10 different oil fields in Nigeria were analysed for 39 elements by Instrumental Neutron Activation Analysis (INAA). Significant correlations were found between Ni and V concentrations and Ni versus Se concentrations. The American Petroleum Institute (API) gravities are inversely correlated with total transition metal concentration of the oils but there is no obvious correlation of the V/Ni ratio with the age of the oil fields. The oils are very similar to North Alaska Type B oils in key transition metal parameters and cluster analysis results using the transition metals as variables indicate that the oils might have been formed from two closely related sources.

Restricted access