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Neutron activation analysis was used to analyse Zn concentrations in high-purity GaAs. A combination of chemical separation of the neutron-induced 65Zn from the GaAs-matrix with anion-exchange chromatography and ultra low-level gamma-ray spectrometry in an underground laboratory was applied. Zn concentration ranged from 2.1 to 51 ng g(-1), and detection limits from 0.018 to 0.059 ng g(-1) were obtained.
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Instrumental neutron activation analysis (INAA) and pseudocyclic INAA (PCINAA) have been used to determine the selenium content of a variety of Canadian food items. Use of the 162-keV gamma ray of short-lived 77mSe in INAA allowed relatively simple and rapid determinations and was suitable for many of the foods. PCINAA was found to give lower detection limits and was used for the low-selenium food samples. Both internal and external quality assessments were used to evaluate and assure the accuracy and precision of the methods developed.
Bordetella pertussis, the causative agent of whooping cough, releases pertussis toxin in an inactive form. The toxin consists of an A protomer containing one S1 peptide subunit and a B oligomer containing several other peptide subunits. The toxin binds to cells via the B oligomer, and the S1 subunit is activated and expresses ADP-ribosyltransferase and NAD glycohydrolase activities. Treatment of purified toxin with dithiothreitol (DTT) in vitro increases both activities. ATP and the detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS) synergistically reduce the A0.5 (activation constant) for DTT from greater than 100 mM to 200 microM. We studied the structure-activity relationships of activators of the toxin. In the presence of CHAPS (1%) and DTT (10 mM) the following compounds increased the NAD glycohydrolase activity of the toxin with the following A0.5's in microM and fraction of the ATP effect in parentheses: ATP, 0.2 (1.0); ADP, 6 (0.8); UTP, 15 (0.7); GTP, 35 (0.6); pyrophosphate, 45 (0.7); triphosphate, 60 (0.6); tetraphosphate, greater than or equal to 170 (greater than or equal to 0.4). Thus, the polyphosphate moiety is sufficient to stimulate the toxin, and the adenosine moiety confers upon ATP its extraordinary affinity for the toxin. Phospholipid and detergents could substitute for CHAPS in the activation of the toxin. Glutathione substituted for DTT with an A0.5 of 2 mM, a concentration within the range found in eucaryotic cells. Thus, membrane lipids and cellular concentrations of glutathione and ATP are sufficient to activate pertussis toxin without the need for a eucaryotic enzymatic process.
The distribution coefficients in n-octanol/water and the RM values in two different solvents have been determined for 12 newly synthetized sulphur-containing pyridazines. The establishment of dose-effect curves by means of three screening methods (writhing syndrome, tail flick test and hot-plate test) permitted to estimate the analgetic activities of the substances under investigation. Regression analyses revealed a highly significant correlation between the ED50 values and the RM values of the pyridazines in butanol/glacial acetic acid/water. The greatest analgetic effect was observed with compounds, the RM values of which tended to 0. To complement this study, the LD50 values and the side-effects on the central nervous system wee considered, too. There was no correlation between the LD50 values and the distribution coefficients; however, a low-significant correlation existed between the side-effects on the central nervous system (as measured by the failure rates in the rotarod test) and the distribution coefficients. In summary, the results hitherto obtained permit to conclude that four of the twelve pyridazines excel by "favourable" analgetic activities. Considering the therapeutic quotients, further investigations, especially of one of these compounds, 3-amino-4-mercapto-6-methylpyridazine, seem justified.
Instrumental neutron activation analysis was carried out to obtain the normal concentration of trace elements in bovine tissues (heart, liver, kidney, spleen, lymph nodes) and serum. Concentrations of 17 elements were determined. In this paper, concentrations of Al, Br, Cs, In and Rb are given and correlations of concentrations are discussed between Cl and Br and between K and Cs or Rb. Significant positive correlations have been found between Cl and Br concentrations in all tissues, between K and Cs concentrations in tissues excluding kidney, and between K and Rb concentrations in tissues excluding liver.
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Using neutron activation analysis and radiometric measurements, the vertical distribution of six possible pollutant elements (Zn, Cr, Co, As, Sb and Br), two trace elements of natural origin (Sc and Hf) and radioactive 137Cs were determined in three lakes, Furtuna, Lung and Mesteru, located in an active sedimentary zone of the Danube Delta. The accumulation rate of recent sediments was estimated from radiocesium profiles. Zn, As, Sb and Br were identified as possible pollutants. The vertical profiles of their concentrations reflect recent historic inputs, showing a gradual increase until around 1990, followed by a continuous decrease.
Instrumental neutron activation analysis (INAA) has been applied to multielemental determinations of medicinal extracts obtained from the plants. Cordia Verbenacea DC, Folidago Microglossa DC, and Petiveria Alliacea. Concentrations of the elements Al, Br, Ca, Cl, Co, Cs, Fe, K, La, Mg, Mn, Na, Rb, Sb, and Zn have been determined in dried extracts of these herbs by short and long irradiations under a thermal neutron flux of 10(11)-10(13) n/cm2s in the IEA-R1 nuclear reactor. The NBS Tea Leaves (1572) and NIES Pepperbush (1) reference materials were analyzed simultaneously with the plant extracts. The results obtained in these analyses have shown a good accuracy and reproducibility of the method. The relative errors and the relative standard deviations were less than 10% for most of the elements analyzed.
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Effective utilisation of neutron activation analysis (NAA) for the elemental analysis of biomedical samples with or without a radiochemical separation, especially when optimal Ge(Li) well type detectors are employed for the acquisition of complex spectra, is demonstrated by determining normal values for 25 elements in bovine liver. Optimal conditions for the determination of Ag, Br, Cl, Co, Cs, Fe, I, K, Mn, Na, P, Rb, Sb, Sc, Se and Zn with the aid of instrumental thermal neutron activation analysis (INAA) by varying the irradiation and decay time are presented. Where INAA was inadequate, simple post irradiation separation based on ion-exchange has been used to determine such elements as Au, Ca, Cd, Ce, Cr, Cu, La, Mo and W. Results from the IAEA intercomparison run for animal muscle (H-4) are also given. The influence of sample size with respect to within-tissue variation of the bulk and trace elements in liver and the contamination of liver samples from the interfering components such as residual blood are also discussed.
Three different neutron activation analysis methods have been developed for the determination of ppb levels of iodine in food samples. The methods are based on the separation of iodine using (i) toluene extraction followed by bismuth sulfide coprecipitation; (ii) bismuth sulfide coprecipitation followed by radiochemical purification with palladium iodide; and (iii) radiochemical isolation by bismuth sulfide coprecipitation. The accuracy of these methods was evaluated by analysing replicate samples of reference materials. The measured values of iodine in A-11 Milk Powder, H-4 Animal Muscle and H-9 Mixed Human Diet from the International Atomic Energy Agency (IAEA) are statistically indistinguishable from the IAEA recommended values, and those for the Standard Reference Materials 1571 Orchard Leaves and 1577 Bovine Liver from the National Institute of Standards and Technology (NIST) are in good agreement with the NIST information values. The precision, in terms of relative standard deviation, is 5% at 50-100 ppb and 10% at 5-20 ppb levels of iodine. The absolute detection limits of these methods vary between 0.5 and 10 ng of iodine. All three methods were used to measure the iodine content of several food samples. The method involving bismuth sulfide coprecipitation followed by radiochemical purification provides the best detection limit and highest precision.
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Epithermal instrumental neutron activation analysis (EINAA) has been used to determine the iodine content of many individual food materials that constitute the typical Libyan diet. The selected samples include different varieties of local and imported foods such as wheat and barley products, rice, bread, legumes such as chick peas and lentil, table salt, and commonly used spices, including thyme and fenugreek. Both conventional and anticoincidence gamma-ray spectrometry techniques have been employed. Epithermal INAA in conjunction with anticoincidence counting has been found to provide the most reliable results. For quality control purposes, a number of NIST biological reference materials were analyzed. The range of daily dietary intake has been calculated as 100-180 microg of iodine per day, which is within the recommended range. Bread was identified as a significant source of iodine in the Libyan diet, as it contributed 99 microg/d.
The accurate measurement of the maximum possible number of elements in ancient ceramic samples is the main requirement in provenance studies. For this reason neutron activation analysis (NAA) and X-ray fluorescence (XRF) have been successfully used for most of the studies. In this work the analytical performance of inductively coupled plasma-optical-emission spectrometry (ICP-OES) and inductively coupled plasma-mass spectrometry (ICP-MS) has been compared with that of XRF and NAA for the chemical characterization of archaeological pottery. Correlation coefficients between ICP techniques and XRF or NAA data were generally better than 0.90. The reproducibility of data calculated on a sample prepared and analysed independently ten times was approximately 5% for most of the elements. Results from the ICP techniques were finally evaluated for their capacity to identify the same compositional pottery groups as results from XRF and NAA analysis, by use of multivariate statistics.
In vivo neutron activation analysis was used to measure total body sodium and chlorine in 18 male and 18 female normal adults. Corrections for body size were developed. Normalisation factors were derived which enable the prediction of the normal levels of sodium and chlorine in a subject. The coefficient of variation of normalised sodium was 5.9% in men and 6.9% in women, and of normalised chlorine 9.3% in men and 5.5% in women. In the range examined (40-70 years) no significant age dependence was observed for either element. Total body sodium was correlated with total body chlorine and total body calcium. Sodium excess, defined as the amount of body sodium in excess of that associated with chlorine, also correlated well with total body calcium. In females there was a mean annual loss of sodium excess of 1.2% after the menopause, similar to the loss of calcium.