The paper reviews the author’s experience acquired and achievements made in methodological developments of neutron activation
analysis (NAA) of mostly biological materials. These involve epithermal neutron activation analysis, radiochemical neutron
activation analysis using both single-and multi-element separation procedures, use of various counting modes, and the development
and use of self-verification principle. The role of NAA in the detection of analytical errors is discussed and examples of
applications of the procedures developed are given.
A simple neutron activation method is described for platinum determination in urine and serum of dogs when studying the pharmacokinetics
of cisplatin, an antitumour drug. The procedure is based on the nuclear reaction198Pt(n, ψ, β−)199Au, a radiochemical separation of gold, and gamma-spectrometry of the radionuclide199Au. Gold is separated as metal by coprecipitation with selenium after the addition of ascorbic acid in a highly acidic medium.
The interference contribution of199Au originating from stable gold is evaluated, too.
The instrumental neutron activation analysis technique (INAA) was used for homogeneity tests and certification analyses of coal fly ash reference materials ENO, ECH, and EOP prepared at the Institute of Radioecology and Nuclear Techniques (IRANT), Koice, Czechoslovakia. Quantitative estimation of a degree of inhomogeneity was suggested. The relative standard deviations due to inhomogeneity were found to be <1% for macroconstituents and <3% for minor and trace elements for sample weights about 25 mg. The results of determination of the elements Al, As, Ba, Ca, Ce, Co, Cr, Cs, Dy, Eu, Fe, Ga, Hf, In, K, La, Mn, Na, Nd, Ni, Rb, Sb, Sc, Sm, Sr, Ta, Th, Ti, U, V, W, and Zn were compared with the IRANT certified or information values. NBS SRM 1633a Trace Elements in Coal Fly Ash was also analyzed as a control sample and the results for the above elements were compared with the NBS certified, information or literature available values. From these comparisons, inference was made on the quality of the IRANT specified values for the element contents.
Elements Al, As, Au, Br, Cl, Co, Cr, Cu, Fe, Hg, K, La, Mn, Mo, Na, Sb, Sc, Sm, V, and Zn were determined by INAA in several
brands and batches of high pressure polyethylene (PE) Bralen (Slovnaft Bratislava, Czechoslovakia). A large scatter of trace
element contents was found in both granules and foils, indicating an inhomogeneous distribution for the majority of the above
mentioned elements present as impurities in PE. Larger amounts of the elements Al, Mn, and Sb were found in foils than in
granules. Blank values resulting from using of PE Bralen as a canning material for INAA were compared to trace element concentration
in human hair samples, too.
Cadmium losses on wet and dry ashing were studied using tomato leaves with metabolized109Cd radiotracer. The most appreciable Cd losses (up to 35%) occured when sulphuric acid was used on wet ashing due to Cd retention in the CaSO4 precipitate formed. Only trace amounts of Cd were retained in a silicaceous precipitate resulting from wet ashing in the absence of sulphuric and hydrofluoric acids in the decomposition mixtures employed. Small Cd losses (up to 7%) were observed on dry ashing in the air in open systems at temperatures not exceeding 500°C. Cd losses increased, however, to 30% when the final ashing temperature was raised to 900°C. Incorporation of the109Cd radiotracer into various parts of tomato plants and its distribution between soil and the plants are also briefly reported.
The instrumental neutron activation analysis technique (INAA) was used for homogeneity tests and certification analyses of the coal fly ash reference material ECO prepared at the Institute of Radioecology and Applied Nuclear Techniques (IRANT), Koice, Czechoslovakia. The relative standard deviations due to inhomogeneity were found to be <3% for 19 elements including for sample weights about 50 mg. The results of determination of the elements Al, As, Ba, Ca, Ce, Co, Cr, Cs, Dy, Eu, Fe, Ga, Hf, In, K, La, Mn, Mo, Na, Nd, Ni, Rb, Sb, Sc, Sm, Sr, Ta, Th, Ti, U, V, W, and Zn, were compared with the IRANT certified or information values. Inference was made on the reliability of the IRANT specified values for the element contents.
The elements As, Cd, Cu, Hg, Mo, Sb, and Se were determined in the biological reference materials (RMs) Bowen's Kale, NIST SRM-1577 Bovine Liver, NIST SRM-1549 Milk Powder, and Versieck's 2nd Generation Biological RM Human Serum using two newly developed radiochemical neutron activation analysis (RNAA) procedures. The first is based on sample decomposition in a mixutre of H2SO4+HNO3+H2O2 and simultaneous extraction of the elements As, Cd–In, Cu, Mo, and Sb by 0.025M Zn(DDC)2 in chloroform from 2–4M H2SO4 in the presence of 0.01M KI. The second consists of sample decomposition in HNO3 in teflon bombs heated at 150°C, Hg extraction by 0.01M Ni(DDC)2 in chloroform from about 1M HNO3, and Se precipitation by ascorbic acid from about 1M HClO4. The RNAA procedures were also used for intercomparison analyses of A and P NIST Leaf Materials (NIST candidate SRM-1515 Apple Leaves and NIST SRM-1547 Peach Leaves, respectively), and CZIM Bovine Liver 12-02-01 RM. Very good agreement of results with certified and/or literature values proved the high accuracy of these determinations by the proposed RNAA procedures, even at the sub-ng/g levels.
Using radiochemical separation of cobalt following the fast neutron reaction58Ni(n, p.)58Co and long high fluence irradiation, we attempted to improve the determination limit for Ni to the nanogram and sub-nanogram level. A Compton suppression spectrometer was shown to be the best choice compared to co-axial or well-type HPGe detectors. Results for low level biological reference materials such as serum and milk powder are discussed. Use of both dried and pre-ashed samples showed that losses of Ni and Co on ashing are non-significant. The influence of the silica ampoule blank was also investigated.
Autopsy of 29-year old woman suspicious of committing suicide by the ingestion of As2O3 yielded contradictory findings. All pathological findings as well as clinical symptoms suggested acute poisoning, while a
highly elevated As level of 26.4 μg g−1 in her hair collected at the autopsy, which was determined with inductively coupled plasma mass spectrometry indicated chronic
poisoning. To elucidate this discrepancy, instrumental neutron activation analysis (INAA) with proven accuracy was performed
of another set of sectioned hair samples. Levels of As found by INAA in the range of 0.16–0.26 μg g−1 excluded chronic poisoning, because the person died after approximately 14 h after the As2O3 ingestion. Two reasons for the discordant As results obtained by ICP-MS and INAA are considered: (1) accidental, non-removed
contamination of hair on the As2O3 ingestion; (2) erroneous performance of ICP-MS.
Recoveries of selected elements were studied for fast decomposition of biological and other materials using alkaline-oxidative
fusion in a mixture of NaOH and Na2O2 at 850–900 °C. The procedure yields total mineralization of samples within 2 to 3 minutes. It is especially suitable in radiochemical
activation analysis (RAA) for the determination of elements forming short-lived radionuclides. Recoveries of the elements
F, Si, S, Cl, Ti, V, Mn, Ge, As, Br, Mo, Ru, In, Sb, I, Re, Os, and U determined using radiotracers were in the range 95–100%,
while those for Se and Hg were significantly lower and highly variable.