Epithermal instrumental neutron activation analysis with Compton suppression spectrometry for the determination of iodine in food samples

Epithermal instrumental neutron activation analysis (EINAA) together with Compton suppression system were optimized and used to analyze several food samples for the determination of low levels of iodine. The method involved the irradiation of samples in the outer epi-cadmium site of the Dalhousie University Slowpoke-2 reactor facility. The samples were then counted directly without any chemical treatment on an anticoincidence counting system. This system comprised a 25 cm³ hyperpure Ge detector, a guard detector consisting of a 10"×10" NaI(Tl) annulus with five photomultiplier tubes (PMTs) and a 3"×3" NaI(Tl) plug with one PMT. Iodine was quantitatively analyzed using the 443 keV photopeak of ¹²⁸I. The precision and accuracy of the method were evaluated using real samples and biological reference materials, respectively. The precision of the method was calculated as percent relative standard deviation and in all cases was within ±5%. The agreement between our iodine values and those of the certified values was generally within ±10%, suggesting an excellent accuracy of the method. The detection limits of the various samples calculated, with the lowest value of 20 ppb. The values of iodine determined ranged between 24 to 3080 ppb. The methods and results are presented.     

H/D isotope effect of 1H MAS NMR spectra and 79Br NQR frequencies of piperidinium p-bromobenzoate and pyrrolidinium p-bromobenzoate

H/D isotope effects onto ⁷⁹Br NQR frequencies of piperidinium p-bromobenzoate were studied by deuterium substitution of hydrogen atoms which form two kinds of N–H?O type hydrogen bonds, and the isotope shift of ca. 100 kHz were detected for a whole observed temperature range. In addition, ¹H MAS NMR spectra measurements of piperidinium and pyrrolidinium p-bromobenzoate were carried out and little isotope changes of NMR line shape were detected. In order to reveal effects of molecular arrangements into the obtained isotope shift of NQR frequencies, single-crystal X-ray measurement of piperidinium p-bromobenzoate-d2 and density-functional-theory calculation were carried out. Our estimation showed the dihedral-angle change between piperidine and benzene ring contributes to isotope shift rather than those of N–H lengths by deuterium substitution.     

Epithermal instrumental neutron activation analysis for the determination of gold and arsenic in Ghanaian gold tailings using conventional and anti-coincidence counting

Epithermal instrumental neutron activation analysis (EINAA) together with both conventional and anti-coincidence counting techniques were used to analyze six different gold tailing samples from Ghana for Au and As. The method involves the use of the epi-cadmium site of the Dalhousie University Slowpoke-2 reactor facility for the irradiation of the samples. After irradiation, the samples were counted directly on the detectors. The identification and quantification of the elements were done using 411 keV photopeak of ¹⁹⁸Au and both 559 keV and 657 keV photopeaks of ⁷⁶As. The precision and accuracy of the method were evaluated. Values for Au in the samples ranged from 2.48 ppm and 6.76 ppm and for As between 1,550 ppm and 3,460 ppm. The values obtained using the two counting systems were in good agreement while the anti-coincidence counting system gave values of higher precision and accuracy. The detection limit for Au were 20 and 10 ppb for the conventional and anti-coincidence spectrometric systems, respectively, and 50 ppb for As in both cases. Details of the method and results are presented.     

Trace elemental analysis of Nigerian crude oils by INAA using miniature neutron source reactor

Copper foils of 10 and 20 mm thickness were exposed to deuteron beams of 2.0 and 2.5 MeV. To avoid structural damage of the targets by high beam intensities, during extended irradiation periods of at least ten hours, liquid nitrogen was used as a refrigerant. Under these conditions equilibrium temperatures of less than 100 °C were achieved. This revised version was published online in August 2006 with corrections to the Cover Date.     

The impact of small-scale mining activities on the levels of mercury in the environment: The case of Prestea and its environs

To obtain the baseline information of mercury pollution due to gold mining activities in Prestea and its environs total mercury (T-Hg) concentrations were measured in water and stream sediment. The samples were analyzed by instrumental neutron activation analysis (INAA). They were irradiated and counted without any preconcentration. Higher levels of T-Hg concentration were found in samples at the sites with extensive small-scale galamsey gold mining activities than at the sites with low small-scale galamsey activities. Concentrations varied between 6.80–19.82 mg/l for water and 28.90–84.30 mg/kg in sediment at sites with extensive small-scale mining activities. At low small-scale mining sites concentration levels for T-Hg varied between 0.50–9.10 mg/l and 1.20–22.75 mg/kg in water and sediment, respectively. The concentration levels of T-Hg in water from all the sampling sites are in excess of the WHO tolerable limit of 0.001 mg/l for drinking water.Some financial support for the work from the National Nuclear Research Institute is highly appreciated. The authors thank Messers Nick Opata and Ekow Quagraine, the technicians at the NAA laboratory for their contribution during preparation, irradiation and counting of samples. We also thank the team of reactor operators.     

Determination of elemental and nutrient composition of water,clam mantle and shell of the Volta clam (<Emphasis Type="Italic">Galatea paradoxa</Emphasis>) using neutron activation analysis

The Volta clam Galatea paradoxa is a highly priced shellfish providing nutrition, jobs and poverty alleviation for the inhabitants of the lower Volta estuary. Clams are filter feeders straining particulate materials in the surrounding water, thus concentrating microorganisms and other metal elements in the gut and mantle which present possible health hazards. The elemental composition of the water, clam mantle, gut, shell, and bottom sediments were determined using Neutron Activation Analysis for the presence of Ca, Cl, Cu, Mg, Mn, V, Fe, Co, Br, Na and K. Proximate analysis of the mantle for the levels of protein, fat, carbohydrate, ash, wood fiber, phosphorus, free fatty acids and energy were carried out using the method of the Association of Official Analytical Chemists. The riverine water was laden with heavy metals V, Co, Cu, Mn, and Fe, as well as Al. These same metallic elements were detected in higher concentrations in the bottom sediments. Bioaccumulation factor (BAF) which is the measure of the distribution of heavy metals between water and biota (Clam mantle and gut), ranged from 2 to 145 times, depending on the type of contaminant. The clam meat contained high protein (15.3 ± 0.2%), no crude fiber, low fat content (1.80 ± 0.11%), fatty acids as oleic (25.2 ± 0.1%), energy (85.5 ± 0.21 kcal/100 g), carbohydrates (22.10 ± 0.03%), P (485 ± 1 mg/100 g), Ca (793 ± 75 mg/kg), Mg (860.3 ± 90.0 mg/kg). The high concentration of Ca (21,402.7 ± 797.0 mg/kg), Fe (18,071.2 ± 94.0 mg/kg), K (96 ± 14 mg/kg), Mg (540.8 ± 81.1 mg/kg), Na (4,570.0 ± 0.2 mg/kg) gives credence to the use of the shell for poultry feed mineral supplements, and in the emulsion paint manufacturing industry.     

Simultaneous determination of short-to-medium lived nuclides in Ghanaian food items using INAA and Compton suppression counting

Summary An instrumental neutron activation analysis (INAA) method was developed for the simultaneous determination of 19 elements in 10 individual food items from Ghana. The samples were irradiated for 1 minutes in a neutron flux of 2.5.     

Instrumental Neutron Activation Analysis of Iodine Levels in Fourteen Seaweed Species from the Coastal Belt of Ghana

Fourteen seaweed species were sampled from October 1997 to May 1999 along the rocky shores of Ghana, which is being washed by the Gulf of Guinea (part of the Atlantic Ocean). Instrumental neutron activation analysis (INAA) was used to measure the iodine levels in the species, with the basic aim of selecting seaweed species that are rich in iodine and hence can be used as supplement in the diet of humans. This is to help solve the problems associated with iodine deficiency disorders (IDD). The levels of iodine found in the seaweed species ranged between 55 to 804 ppm. The precision, expressed in terms of relative standard deviation, and accuracy of measurements are within ±5–10%. The results show high variability in and between species and among sampling sites. The high values of iodine concentrations in the macroalgae suggest that these marine organisms can be used as supplement in the diet of humans.     

Evaluation of the robustness of estimating five components from a skin spectral image

Optical Review - We evaluated the robustness of a method used to estimate five components (i.e., melanin, oxy-hemoglobin, deoxy-hemoglobin, shading, and surface reflectance) from the spectral...