Multivariate analysis applied to some elements in human fluids and whole bloods of hemodialysis patients determined by INAA

This research is a framework of a big project aimed to the knowledge of human metabolism in hemodialysis patients. For reaching high sensitivity and obtaining accurate values for elements at very low concentrations Instrumental neutron activation analysis (INAA) was used for its characteristics to be a primary analytical method and because it does not require any chemical–physical pretreatment. The samples analyzed (160) are representative of groups of homogeneous population and specific matrices (hemodialysis fluids and whole human blood). The irradiation was performed in the rotating rack (Lazy Susan) of the Triga Mark II reactor of the R.C. Casaccia-ENEA at a neutron flux of 2.6 × 10¹² n cm^?2 s^?1 with an irradiation time of 12 h. The results on the hemodialysis fluids report the values and the behavior of selected trace elements: the levels of Br and Na show a decrease between the pre- and post-dialysis whereas Fe, K and Zn an increase. The other elements such as Cs, Rb and Se seem to keep constant between the two phases. Similar data are found for the whole human blood for the same selected elements. Finally, exploiting the INAA peculiarity it has been investigated the levels of trace and ultra-trace elements interesting from a toxicological (Hg, Ni, Sb) and nutritional (Co, Cr) point of view and seldom determined due to their analytical implications. Finally, a chemiometric investigation performed through dendrogram trees, Canonical discriminant analysis and principal component analysis, has evidenced the similar effects of the HF, HDF and BIC-treatments on the investigated fluids respect to the CAPD dialysis.     

Determination of silicon in natural and pollution aerosols by 14-MeV neutron activation analysis

The determination of silicon via the ²⁸Si(n,p)²⁸ Al reaction by means of 14-MeV neutrons is applied to the analysis of pollution and natural aerosols. A Whatman 41 filter (40 cm²) on which airborne particulate material has been collected is compressed into a 3 × 12.7 mm pellet. Standards are prepared in the same way from clean filters spiked with a silicate solution. After a 50-s irradiation and a 75-s decay time, the sample is counted for 2 min with 5” × 5” NaI(Tl) well detector. The 1.779-MeV photopeak of ²⁸Al is measured with a single channel sealer chain or with a multichannel analyser. The reproducibility, sensitivity and liability to interference from other elements were investigated for both counting systems. The homogeneity of the pellets and the filters was checked. The overall precision of one single-channel determination was estimated to be 3.5% after a 24-h high-volume sampling time. Samples collected in urban, industrial and remote areas with concentrations ranging from 0.05 to 15 μg Si m^-3 air were analysed and the results are discussed.     

Instrumental neutron activation analysis of spruce needles and trees

Tree rings and needles of young spruce clones from the immission area of the Al-refinery Ranshofen (Upper Austria), which had ceased production in 1992, were investigated by INAA. Short time irradiation was performed for determining, Al, Mn, Ca and Cl, while the elements Na, K, Rb, Ba, Zn, Fe, Sc, Cr, Co, Br and in some samples also Ca were determined via middle- and long-lived radioisotopes. Irradiation and counting conditions are given. Accuracy and sensitivity are sufficient to describe the trends of the element concentrations in needles and with the exception of Cr, Sc and Br, in tree rings. Ca-concentrations derived from⁴⁹Ca (short-time irradiation) and⁴⁷Ca (long-time irradiation) are compared and show good agreement Additionally Mg was determined in some samples by ICP-AES and if possble, by INAA. The results are compared.     

156Dy as an activable yield tracer for determination of rare earth elements in biological materials by neutron activation analysis

Use of an enriched¹⁵⁶Dy isotope as an activable yield tracer for the determination of lanthanoid contents in various biological reference materials has been proposed. The method consists of preconcentration of the lanthanoid in the¹⁵⁶Dy doped samples followed by neutron irradiation and further chemical purification steps. The chemical behaviour of lanthanoid elements in the whole procedure was found, in separate runs, similar to that of the added¹⁵⁶Dy within experimental errors. Simple purification steps after irradiation allow the measurement of relatively short-lived nuclides and diminish the radiation dose received during the chemical treatment. The present results for orchard leaves (NBS SRM 1571) are generally in good agreement with the previously reported data. Some new data are obtained for other biological reference materials.     

Alpha activation of calcium and its possible use for analysis

This method is based upon the measurement of 3.95-hr⁴³Sc which is formed during α-activation from⁴⁰Ca, the most abundant (96.8%) isotope of calcium. The excitation function for the⁴⁰Ca(α, p)⁴³Sc reaction was determined and the maximum yield of⁴³Sc (about 10⁷ cpm per mg of calcium for a 1-hr irradiation at a beam current of 1 μA) was obtained at an irradiation energy of 14 MeV. The interference free sensitivity of the method at this energy was found to be 8.5·10^?12 g, for a 1-hr irradiation at a beam current of 10 μA. The elements most likely to interfere with the determination are potassium and scandium. The extent of this interference was investigated as a function of irradiation energy and methods to eliminate or subtract the activity formed from these elements are discussed. An attempt was made to determine non-destructively the calcium content of very pure silicon and aluminium and upper limits for the concentration of calcium in these samples were set at 0.27 ppb and 6.9 ppb, respectively. Magnesium, thulium oxide and yttrium oxide samples of known calcium content were also analysed.     

Determination of sodium and chlorine in pure water by neutron activation analysis

Neutron activation analysis was applied to determine sodium and chlorine in high purity water samples. After irradiation of the sample,³⁸Cl was purified from⁸²Br and other nuclides by carbon tetrachloride extraction and silver chloride precipitation, and²⁴Na was separated from other alkali elements and other nuclides by adsorption of²⁴Na on HAP. The activities of both elements were measured by conventional G.M. counter. The contamination of the elements from container walls during neutron irradiation and the interference with³⁸Ar(n, p)³⁸Cl reaction on argon dissolved in water were also examined. Water samples containing 3 ppb of chlorine could not be determined accurately, owing to the above mentioned interfering reaction.     

Determination of some elements by epithermal neutron activation analysis for the Arctic aerosol

Summary We have determined nineteen trace elements in 685 aerosol filter samples collected during 1964-1978 in northern Finland by the Finnish Meteorological Institute. In this paper we present some procedures and results for very short (~25 s), short (~3-54 min), and medium (12-35 h) lived isotopes as determined by epithermal NAA in conjunction with and without Compton suppression. Elements with a I_γ/σthratio are favorable to be determined by epithermal NAA. Silver was determined by a one minute epithermal irradiation because of a very short ¹¹⁰Ag half-life. Antimony, arsenic, cobalt, bromine, indium, iodine, potassium, silicon, tin, tungsten, and zinc were determined by a ten minute epithermal irradiation. For silver determination, samples were counted without transferring the filter from the irradiated vial, however, for ten minute irradiation all samples were transferred to a non-irradiated vial and counted both in the normal and Compton mode by the HPGe gamma-spectrometry system with a decay time of about 10 minutes and counting time of 15 minutes. Each day a maximum of 16 samples were irradiated and immediately following the short counting, these samples were loaded into an automatic sample changer in sequence of irradiation and counted for an hour in both normal and Compton modes. This has proven to be an extremely cost effective measure thus reducing the need to employ long-lived NAA to analyze other elements such as Ag, Co, Sn and Zn and Ag for air pollution source receptor modeling.     

Multielement analysis of uraniferous rocks by INAA: Special reference to interferences due to uranium and fission of uranium

The presence of uranium in a sample enhances the true values of La, Ce, Nd, Sm determined by INAA if appropriate corrections are not made for the interference. The enhancement of the true values comes about because the (n, γ) activation products of these elements, viz.¹⁴⁰La,¹⁴¹Ce,¹⁴⁷Nd,¹⁵³Sm, are also produced from the fission of²³⁵U (～0.72% natural isotopic abundance) even when La, Ce, Nd, Sm are totally absent in the given sample. In a 5 hour irradiation 1 μg of U is found to be equal to 0.28 μg of Ce and 0.23 μg of Nd while the equivalent La is found to be dependent upon the delay from end of irradiation to sample counting time. A numerical procedure is given to correct for these interferences. Spectral interferences from fission and (n, γ) β products of uranium in the determination of other trace elements by INAA is also investigated. Uranium is found to be determined best using the 278 keV gamma-ray of²³⁹Np.     

New Developments in Activation Analysis for Material and Environmental Sciences

Activation analysis in general and mainly reactor neutron activation analysis (NAA) has been used extensively for measuring trace elements in high purity materials, particularly semiconductor materials. The advantages of NAA in determination of trace elements differ from one semiconductor material to another. For all of them the inherent properties of activation analysis especially those of non contamination with the reagents, low blanks and high sensitivity are the reasons for the choice of NAA as the main analytical procedure. These inherent properties are essential for analysis of high-purity materials where concentrations of ppb's and sub ppb's have to be measured. NAA is specially suitable for the determination of trace elements in silicon due to the very short lived very low activity induced by neutron reaction in silicon. This enables easy instrumental (i.e. without chemical separations) determination of trace elements in silicon. In the HFR reactor at Peten, Netherlands, a special facility was constructed for irradiation of silicon samples of Philips, in which silicon wafers of up to 15 cm diameter can be irradiated with 4 × 10¹³n. cm^?2. sec^?1 and the irradiation is done for 72–96 hours. using large Ge(Li) detectors (100 to 150cc) and long counting time (8–16 hours) they measured 22 elements in concentrations below ppb and 10 others between ppb and 300 ppm. Trace elements in germanium have been determined both instrumentally after very long decay time (100 days) or after short decay time removing the activities from the matrix by chemical separation. Trace elements in GaAs are determined only after chemical separtion. Several other semiconductor material such as Sc, Te, GaP and CuInS₂ were also determined by NAA. Some trace elements cannot be determined by neutron activation. Carbon, nitrogen and oxygen are determined by activation with protons, alphas or ³He particles. Boron and hydrogen are determined by prompt emission induced by charged particle activation, which gives not only the total concentration but also the depth profile. Carbon, nitrogen, oxygen and phosphorus were also determined by prompt proton activation analysis. The environmental samples studied by activation analysis can be divided into three categories: atmospheric aerosols, water samples and solid wastes. NAA of atmospheric aerosols have been used for their posible toxicological hazards, their source identification and for studies of atmospheric transport processes.     

Photon and proton activation analysis of iron and steel standards using the internal standard method coupled with the standard addition method

The internal standard method coupled with the standard addition method has been applied to photon activation analysis and proton activation analysis of minor elements and trace impurities in various types of iron and steel samples issued by the Iron and Steel Institute of Japan (ISIJ). Samples and standard addition samples were once dissolved to mix homogeneously, an internal standard and elements to be determined and solidified as a silica-gel to make a similar matrix composition and geometry. Cerium and yttrium were used as an internal standard in photon and proton activation, respectively. In photon activation, 20 MeV electron beam was used for bremsstrahlung irradiation to reduce matrix activity and nuclear interference reactions, and the results were compared with those of 30 MeV irradiation. In proton activation, iron was removed by the MIBK extraction method after dissolving samples to reduce the radioactivity of⁵⁶Co from iron via⁵⁶Fe(p,n)⁵⁶Co reaction. The results of proton and photon activation analysis were in good agreement with the standard values of ISIJ.     

William D. Ehmann, radioanalytical chemist and radiochemistry educator

Copper (Cu) is an essential element and is incorporated in many biomolecules that are involved in protecting the brain from oxidative damage. Many brain regions strongly affected by neurodegene rative diseases are small. A sensitive nondestructive procedure to determine Cu is desirable to preserve samples for additional studies. Copper is not easily determined by instrumental neutron activation analysis (INAA) due to high activity levels produced by major abundance elements such as sodium (Na) and chlorine (Cl), which produce a high Compton background. An INAA method involving a short epithermal neutron irradiation and counting with a Compton suppression system was developed to determine Cu in brain, via 5.1-min⁶⁶Cu. These short irradiation results are compared to those based on coincidence spectrometry of annihilation photons from positron emitting 12.7-h⁶⁴Cu after a long irradiation.     

Destructive and nondestructive analysis of some elements in tissue and environmental samples by thermal neutron activation analysis technique

A rapid and selective method has been developed and applied for determining elements present in tissue and environmental samples by both destructive and nondestructive activation analysis. Nondestructive activation analysis involves the irradiation of the sample and standard of the elements such as Mn, Na, and K with thermal neutrons from²⁵²Cf neutron source followed by radioassay of the (n,r) products on a HPGe detector coupled to a PC-based MCA. Elements are determined by irradiating the samples in the thermal neutron flux of the CIRUS reactor and radiochemically separating the isotopes of interest using substoichiometric extraction and precipitation technique. The statistical evaluation of the method with respect to accuracy and precision of the method and its sensitivity are discussed.     

Extended automated separation techniques in destructive neutron activation analysis; application to various biological materials,including human tissues and blood

An automated post-irradiation chemical separation scheme for the analysis of 14 trace elements in biological materials is described. The procedure consists of a destruction with sulfuric acid and hydrogen peroxide, a distillation of the volatile elements with hydrobromic acid and chromatography of both distillate and residue over Dowex 2X8 anion exchanger columns. Accuracy, precision and sensitivity are tested with reference materials (BOWEN’s kale, NBS bovine liver, IAEA materials dried animal whole blood, wheat flour, dried potatoes, powdered milk, oyster homogenate) and on a sample of pooled human blood. Blank values due to trace elements in the quartz irradiation vials are also discussed.     

Controle de la purete d'echantillons de nickel par spectrometrie-γ directement apres irradiation au moyen de neutrons thermiques

Purity control of high-purity nickel by direct γ-spectrometry after irradiation with thermal neutronsThe possibilities of analysing high-purity nickel samples by direct γ-spectrometry with a Ge(Li) detector after neutron activation are described. The samples (300—600 mg) are irradiated for 65 h in a thermal neutron flux of 5 X 10¹² n cm^-2 s^-1 and the matrix radioactivity is then allowed to decay for 30 h. It is possible to determine simultaneously 18 elements (the commonest impurities in nickel) by using standards containing known quantities of these elements irradiated under the same experimental conditions. Concentration limits are calculated for 15 elements based on the nuclear characteristics of the radio-isotopes which can be detected by neutron activation. It should be possible to determine 22 elements in nickel samples, at concentrations below 0.1 μg g^-1. The method is suitable for laboratories situated far from irradiation facilities.     

Non-destructive multi-element photon activation analysis of river sediments

A large number of toxic elements, including Th and U, in Scheldt and NBS river sediments, have been determined non-destructively by high energy photon activation. The length of irradiation varies between 1.5 hours for short lived-nuclides and 7–18 hours for long lived-nuclides. The induced activities are measured using a single open-ended coaxial Ge(Li) detector and the photopeak integrations are calculated using the total peak area method and the Cutipie computer program after substraction of the intrinsic background of the detector from each spectrum (Angela program). The photonuclear reactions and the best detection limits for 36 elements are indicated.     

Mineral elements and essential trace elements in blood of seals of the North Sea measured by total-reflection X-ray fluorescence analysis

Mineral and essential trace elements are involved in numerous physiological processes in mammals. Often, diseases are associated with an imbalance of the electrolyte homeostasis. In this study, the concentrations of mineral elements (P, S, K, Ca) and essential trace elements (Fe, Cu, Zn, Se, Rb, Sr) in whole blood of harbor seals (Phoca vitulina) were determined using total-reflection X-ray fluorescence spectrometry (TXRF). Samples from 81 free-ranging harbor seals from the North Sea and two captive seals were collected during 2003–2005.Reference ranges and element correlations for health status determination were derived for P, S, K, Ca, Fe, Cu, and Zn level in whole blood. Grouping the seals by age, gender and sample location the concentration levels of the elements were compared.The blood from two captive seals with signs of diseases and four free-ranging seals showed reduced element levels of P, S, and Ca and differences in element correlation of electrolytes were ascertained.Thus, simultaneous measurements of several elements in only 500 μL volumes of whole blood provide the possibility to obtain information on both, the electrolyte balance and the hydration status of the seals. The method could therefore serve as an additional biomonitoring tool for the health assessment.     

Rapid multielement neutron activation analysis with a slowpoke reactor

The SLOWPOKE nuclear reactor meets many modern elemental analysis requirements; rapid multielement analysis of most types of samples is possible. The variable neutron flux (maximum 10¹² n cm^-2 s^-1) is stable, homogeneous and reproducible from day to day over a period of months. Sensitivities for 78 elements analyzed by neutron activation, with short irradiation and counting periods, have been determined; the conditions allow rapid multielement analysis with short sample turn-round time. Examples of the application of the technique to complex practical samples are given.     

Neutron activation analysis of rare earth impurities in europium oxide

A neutron activation analysis method for determining Yb, Dy, Ho, Sm and La impurities in europium oxide with sensitivities of 10^?5 to 10^?7% is described. The method is based on a preliminary concentration of the rare earth elements by reducing europium(III) with zinc to europium(II), and separating the trivalent rare earth elements by extraction chromatography. After neutron irradiation, the individual radioisotopes of the rare earth elements are separated by using KU-2 cation exchange resin and ammonium α-hydroxyisobutyrate solution as the eluant.     

The determination of sulphur and phosphorus in steel by neutron activation analysis

Sulphur and phosphorus in steel were determined by neutron activation analysis, being counted as ³⁵S and ³²P respectively. For steels with sulphur to phosphorus ratios larger than 10, it seems possible to determine both elements by counting ³²P, making use of a double irradiation technique at different fast to slow neutron fluxes.     

Epithermal neutron activation analysis and its application in the Miniature Neutron Source Reactor

The cadmium and boron ratios from 44 elements, totally 66 nuclides, were determined in the inner and outer irradiation sites of the Miniature Neutron Source Reactor (MNSR). China Institute of Atomic Energy. A permanent Cd-shielded epithermal neutron irradiation site has been designed and installed in the outer of the beryllium reflector of this reactor. Elements e.g., I, Br, Sr, Si, Th and U in biological samples, such as foodstuff, water and blood, geological and environmental samples, such as soil, rock, sediment and vegetable leaves were analyzed by BN-shielded epithermal neutron activation analysis (ENAA), and Au, As, Sb, Th and U by Cd-shielded ENAA. The results show that the detection limits of these elements by ENAA are better by a factor of 1.5–7 than those with conventional NAA.