Phosphorus is selectively extracted as molybdovanadophosphoric acid (MVPA) and determined indirectly using52V. Silicon, germanium, arsenic, fluoride and tannic acid do not interfere. The sensitivity for phosphorus was 1421±13 counts52V per ng P ml–1 with a detection limit of 0.2 ng P ml–1. The precision is ±10% over the range 0.7±70 ng P ml–1. The sensitivity is four orders of magnitude greater than for conventional neutron activation analysis (NAA) using the31P(n, )28 Al reaction and a SLOWPOKE II reactor. Greater selectivity for phosphorus is obtained than by direct measurement of32P by beta ray spectroscopy.
The dependence of self-absorption of X-rays and low energy -rays on energy and sample matrix has been studied for94mNb,128I,104mRh,239U and233Th. Experimentally determined attenuation factors have been compared to calculated values. The use of these nuclides in the instrumental neutron activation of practical samples has been evaluated.
An instrumental neutron activation analysis procedure has been developed which permits the direct determination of Au, Ir, Os and Rh in iron meteorites using a SLOWPOKE reactor. A simple correction method enables the instrumental determination of rhodium using its short-lived nuclide.
X-rays emitted by thallium and bismuth after neutron activation have been examined for their use in the determination of these elements. Interferences have been assessed. Thallium-204,206Tl and210Bi are employed. Detection limits are high but purely instrumental determinations are possible from 50 g per g to fractions of percent levels.
Lead phosphate quantitatively coprecipitates trace amounts of Ag(I), Cd(II), Cr(III), Cu(II), Mn(II), Th(IV), U(VI) and Zr(IV).
The trace elements are determined in the precipitate by instrumental neutron activation analysis (INAA); detection limits
are given. The practical application to the determination of U and Th is described.
Classical activation analysis of fluorine by thermal neutrons has a limited application because of frequent interference from
chlorine, the short half life20F (11.4 s) and too high dead time of detectors. A procedure is described for fluorine determination using19F (n,p)19O reaction. Use of a boron carbide shield has no effect on the activity of19O (boron ratio −1) but considerably reduces background and interference due to18O (n, γ)19O reaction. The technique has been successfully applied to the determination of fluorine in organic compounds even in the
presence of large amounts of chlorine and oxygen.
Authors:S. Muddukrishna, J. Holzbecher, and D. Ryan
Hair samples from Canada, China, India and New Zealand were analyzed by neutron activation analysis. Comparison of the percent manganese in the alkali-soluble fraction of hair with the total manganese concentrations shows that, within groups, the percent manganese concentrations is relatively constant whereas overall concentrations are not. For multiple sclerosis (MS) patients, from Canada and New Zealand, very highly significant differences were observed, between controls and patients, for %Mn in the alkali-soluble fraction.
Authors:M. Bahra, D. Elliott, M. Reading, and R. Ryan
A novel instrument is described called the Thin film Analyser (TFA) which quantitatively measures changes in mechanical and rheological properties of drying films in-situ on a test panel. It is based around a simple force-sensing device, capable of carrying various probes, which can be positioned in anX-Y plane over the panel. Temperature control is achieved by means of a heating block under the sample. By imposing a thermal gradient along the block, measurements can be obtained at a series of temperatures in a single experiment. Several applications of the TFA to the drying of curable and latex-based coatings are discussed, as well as some more specialized uses. The TFA concept represents a novel approach to the thermal analysis of thin films.
Authors:I. Osvath, P. P. Povinec, H. D. Livingston, T. P. Ryan, S. Mulsow, and J.-F. Commanducci
A “sentinel”-type device, equipped with a NaI (Tl)-based underwater gamma-spectrometer mounted on a stationary buoy, transmitting data through satellite connection, was deployed in the north-western Irish Sea.The data recorded and received in real-time indicated that no detectable significant changes occurred in the concentrations of 137Cs at the mooring site in the period September to November, 2000. Other anthropogenic gamma-emitters were not detected.