Iodine is an element with excellent intrinsic sensitivity when determined by thermal neutron activation. However, in most
real samples, the preponderance of chlorine and bromine, relative to iodine, makes the direct determination of iodine virtually
impossible. Over the past 20 years, there probably have been as many publications on the separation of iodine as there have
been for any other radionuclide. Upon review, however, the methods are essentially the same. After irradiation, the samples
are subjected to a rapid destructive process to free the iodine from the matrix and then the iodine is separated from the
other halides either by liquid-liquid extraction or by liquid ion exchange. Both of these procedures are, however, rather
complex and do not effect a complete separation of the halides in one pass. In the work presented here, a simple procedure
is described for the quantitative separation of iodine from chlorine. The procedure utilizes a gas phase separation on hydrated
manganese dioxide with iodine collected on silvered quartz wool. The described procedure has been used for the determination
of iodine in numerous new and old SRM's at the NBS.
Chromium is recognized to be an essential trace element in several biological systems. It exists in many biological materials
in a variety of chemical forms and very low concentration levels which cause problems for many analytical techniques. Both
instrumental and destructive neutron activation analysis were used to determine the chromium concentration in Orchard Leaves,
SRM 1571, Brewers Yeast, SRM 1569, and Bovine Liver, SRM 1577. Some of the problems inherent with determining chromium in
certain biological matrices and the data obtained here at the National Bureau of Standards using this technique are dicussed.
Authors:Hyun-Je Cho, Yong-Sam Chung, and Young-Jin Kim
A prompt gamma activation analysis facility has been constructed on the ST1 horizontal beam port at the HANARO research reactor, KAERI in 2003. The detector system consists of a high-purity Ge detector surrounded by BGO/NaI(Tl) scintillators as an annulus type to reject the Compton scattered photons. Detection sensitivity for boron was obtained from the prompt gamma-ray spectra of boric acid, B(OH)3, containing 0.1-65 μg boron. The net peak for the calculation of the boron concentration was obtained by eliminating the sodium 472 keV peak, involved in the boron 478 keV peak. The biological samples used are NIST SRMs such as Peach Leaves, Apple Leaves, Tomato Leaves, Spinach Leaves, Total Diet, Typical Diet, Oyster Tissue and Corn Bran, etc. The measured values for high boron concentration showed up to a 3% of the relative, but in a low concentration below 5 ppm, present values were higher than the certified ones.
Authors:H. Nakahara, M. Tsukada, A. Moriizumi, K. Horiuchi, and Y. Murakami
The improvement obtained by epithermal neutron activation analysis was studied in terms of the detection sensitivity and precision
in the γ-ray spectrometry for geological and biological reference samples. For geological samples, small improvement was observed
only for the elements As, Ba, Sb, Se and U. For biological samples, however, large improvement was observed for As, Br, Sb
and U. The ratio of the resonance integral to the effective thermal-neutron capture cross section was observed for 19 nuclides.
The effect of the (n, p) reaction to the determination of Al and Mg by the ordinary reaktor-neutron activation analysis was
Instrumental neutron activation analysis (INAA) procedures were optimized for the analysis of small (1 mg) solid samples. This process included sample handling as well as detailed evaluation of high rate counting techniques, also in conjunction with rapidly decaying sources, to establish the necessary analysis environment for the determination of large numbers of samples with high reproducibility. The investigated materials included biological materials such as peach leaves (SRM 1547), lichen, and bovine liver, as well as environmental materials such as urban particulate matter (SRM 1648), and deep ocean sediment. The analytical data obtained with the INAA procedures were used to determine homogeneity values.
On décrit la méthode pour le dosage du hafnium dans des aciers étalons. Cette méthode consiste en une combinaison de l'analyse
par activation neutronique avec un procédé d'extraction par solvant, l'agent d'extraction étant le di (2 ethylhexyl) phosphate.
Enfin, on procède à une extraction en retour dans de l'acide fluorhydrique 2N juste avant la mesure d'activité. La mesure
est faite au moyen d'un détecteur Ge(Li) 60 cc associé à un analyseur 2048 canaux. La méthode d'analyse ainsi décrite permet
une détermination rapide du hafnium avec, une précision de l'ordre de 3 à 4% pour les dosages de routine.
INAA results obtained on 11 vegetal samples proposed as European reference standards, in nutritional, agricultural and analytical studies are reported. A comparison is also reported with the data obtained by 38 European laboratories, by using spectrochemical methods (ICP atomic absorption, X-ray fluorescence, etc.). The usefulness of Instrumental Neutron Activation Analysis (INAA) is stressed, particularly when more usual methods are not sensitive enough for microelements that are important markers of toxic and pollutant substances. To this class belong lanthanides and other rare elements (Sc, Cs, Rb), which can be used both as fingerprint of soil provenance and for evaluating the homogeneity of the sample.
Authors:V. Maihara, M. Gallorini, and M. Vasconcellos
A radiochemical separation procedure based on chromatographic separation using Chelex-100 in 0.1M HAc-0.1M NH4Ac at pH 4.8 and TDO in 6M HCl, has been developed to determine Cd, Co, Cr, Fe, Se, The, U, W and Zn in three biological materials of botanic origin used as SRM's: 1547 Peach Leaves, 1515 Apple Leaves and the new proposed material Spinach. The aim was to obtain more information for these elements whose values are not yet determined or are given only as suggested values.