In recognition of the 1997 anniversary of the first century of radiochemistry, a review is made of its unique contribution
to the emergence of nuclear science, its development from the use of very basic chemical techniques initially to a battery
of more sophisticated procedures, and its changing role as it has become widely applied in many fields of science. Synergistically,
these fields have been able to develop with the aid of radiochemistry while at the same time, radiochemical methods developed
to meet the demands of such applications. Among these, during the second half of the century, has been radiochemistry applied
to quantitative chemical analysis: RAA or, nuclear analytical chemistry, and typical examples of its use in the authors' laboratory
are described, including some recent INAA results on development of novel ‘activable’ tracer coding for forensic use with
specialized and high security materials. The specific contributions, during the century, of Japanese pioneers in radiochemistry
are also cited.
Nuclear methods of analysis have advanced dramatically in recent years, and in many ways, techniques that once were viewed as a scientific curiosity and the toys of a few scientists working in large nuclear research establishments, are now semi-routine and can be applied even by young students. Large amounts of good analytical data are outputted from instruments having sophisticated embedded software. It is interesting to speculate on the directions that nuclear analytical techniques may take next: whether more multielement; more automation for vastly larger sample suites; extension to minor and major components of samples as well as trace components; coupling of nuclear methods to hyphenated methods. However, in some respects the resources needed to continue to develop and apply radioanalytical methods are on the wane: reactors and accelerators are being closed and fewer radiochemical specialists are being trained. The open question, is whether instrumental analysis techniques will offer more and better results with less effort, or be less equipment intensive? In this paper some personal reflections on nuclear actcivation methods and their trends are presented and discussed. Some mileposts in the development of the field and some unique and interesting applications (as implied by the paper title) are cited and discussed.
Epithermal neutron activation analysis (ENAA) was applied to measure quantitatively Cd and other elements in bone samples from control and Cd-fed rats. This method was found to be non-destructive to the bone samples, with no sign of radiolytic charring and was sensitive enough to detect and quantify Cd in bone samples at normal levels for mammals (viz. 0.5–1.0 g/g) and higher. Two different thermal neutron shield materials were utilized, namely cadmium and boron. The boron shield resulted in a 27% improvement in the detection limit of Cd in bone. The accuracy of ENAA for Cd was assessed by intercomparison with electrothermal atomic absorption spectrophotometry (ETAAS), and the results were in fair agreement (±23%) with those from ENAA.
The purpose of this study was to use instrumental neutron activation analysis (INAA) to investigate the effectiveness of oak tree leaves as indicators of atmospheric pollution. Leaves were sampled from several different cities in southwestern Ontario, Canada and tested for 16 different trace elements (U, Dy, Ba, Ti, Sr, I, Br, Mg, Cu, Na, V, K, Al, Mn, Cl and Ca). The results show promise for the use of oak leaves as multielemental environmental monitors due to their apparent ability to reflect the overall pollution levels of the vicinity in which they grow. Oak leaves were found to be superior to both birch and maple leaves for monitoring most of the elements studied.
Photon and thermal neutron activation analysis were used to analyze airborne particulate matter obtained during the period January to March of 1984 for up to thirty elements. Elemental concentrations and meteorological data from the Toronto, Ontario area were subjected to factor analysis and the major sources of particulate deduced. Elemental profiles for six sources, viz. crustal soil, automobile exhaust, road salt, refuse incineration, oil combustion and an unidentified arsenic source, were used in a chemical element balance to quantitatively determine the contribution of each source to the ambient aerosol. Re-entrained soil contributed 67%, automobile exhaust contributed 15% and the other sources contributed lesser amounts to the inorganic particulate matter. Particle-size distributions for nine elements, viz. Al, Fe, Sc, As, Br, Cl, Zn, Mn, V, are presented as an argument for the development of receptor models involving particle-size distribution data.
As part of a larger occupational exposure study in which the concentrations of 18 elements were measured in head hair and toenail collected from steel plant workers, a number of factors associated with interpreting the data obtained were examined. In this paper, some of the limitations and complications associated with hair and nail analysis that were thereby recognised are discussed. Data obtained from the occupational study demonstrated the potential for misinterpreting hair or nail analysis data either through describing results averaged over a group by arithmetic instead of geometric means or through not accounting for the age range of subjects in groups to be compared. Examples that arose from the study indicated that differences between hair from the same subjects grown at different times can both complicate and assist in interpreting hair analysis results. In an investigation into the addition and removal of metallic powders, it was found that both hair and nail can directly incorporate elements through contact with dust.
Photon and thermal neutron activation analysis were used to determine the concentrations of up to thirty elements in aerosol samples collected by cascade impactor in Toronto, Canada during the period July to December of 1985. Examination of the particle-size distributions thus obtained led to the development of a new receptor model. A size-specific elemental mass balance (SSEMB) was used to apportion the mean ambient Pb aerosol concentration amongst four contributing sources as follows: secondary lead refinery emissions (46%), refuse incineration (28%), automotive exhaust (25%) and re-entrained soil and dust (<1%). The predicted concentrations of Al, As, Br, Na, Pb, Sb, and Zn agreed with observed concentrations to within a factor of two for most elements in most particle size fractions.
A total of 35 trace and minor elements including some of environmental significance were determined in each of a selection of 15 Chinese and 6 Canadian thermal coals and their ashes by using the SLOWPOKE-2 nuclear reactor facility of the University of Toronto. The concentrations and distributions of these constituents among the coals and their combustion products (viz. ash and volatile matter) are presented together with an interpretation of their significance in relation to the large scale combustion of these coals as thermal fuels in industrialized countries such as China and Canada. The detailed results showed wide variations in trace impurity concentrations (up to a factor of 100 and more) among the coals studied with few large differences between those of Chinese and Canadian origin except that the rare earths, Sc, Th, U, I, and Se were much higher in the former, other halogens, As and Na were lower. Values for elemental enrichment factors (EF) relative to normal crustal abundances indicated that only As(EF=13), Br(5.7), I(16), S(230), Sb(11) and Se(320) were appreciably enriched in coal. During static ashing at 750°C most of the halogens, S and Se were volatilized whereas most other inorganic constituents were highly retained and concentrated in the ash by factors of 6 to 11.