Determination of mercury and selenium in consumed food items in Libya using instrumental and radiochemical NAA

Summary Instrumental and radiochemical neutron activation analysis (INAA and RNAA, respectively) were used to analyze several consumed food items in Libya for the detection of low level concentrations of mercury and selenium. Selenium was determined using both short- and long-term irradiation, while mercury was determined in the long-term irradiation mode. At RNAA, after wet-ashing of samples in a microwave digestion unit, mercury was extracted with Ni(DDC)₃/CHCl₃, and selenium was precipitated in elemental form with ascorbic acid. For quality control, NIST reference materials were analyzed using the same procedures as for the food samples. The results of the analytical modes used were compared.     

INAA determination of selenium via77mSe in plasma,semen and hair samples from beef and dairy bulls

Interest in the element selenium with respect to its biological significance has been steadily increasing for the last ten years. Neutron activation analysis has long been used for the accurate determination of selenium in biological samples usually via⁷⁵Se. More recently activation analysts having access to high flux reactors with rapid delivery pneumatic tube facilities; have successfully employed^77mSe. This approach, which is much faster, is particularly well suited to the Missouri University Research Reactor (MURR). The specific interest concerning bulls has to do with the involvement of selenium in the reproductive system. Selenium analysis methodology and data on plasma, semen and 22 tissues from both beef and dairy bulls are presented.     

Activation analysis of Se in biological samples through75Se and77mSe

A method is described to separate trace amounts of selenium in biological samples without using a carrier. This method is based on the adsorption on active carbon of the complex ion formed with APDC /ammonium salt of l-pyrrolidine carbodithioic acid/ at pH 1. The efficiency of the radiochemical separation described is measured by using carrier-free⁷⁵Se labelled solutions of sodium selenite at selenium concentrations from 3.5×10^–8 to 3.5×10^–11 g ml^–1. The results were between 95% and 98% with statistical variations from 2% to 10%. The determination of selenium can be made following this separation either through⁷⁵Se in the traditional way, or through^77mSe if the separation is performed prior to irradiation. The detection limits on the available conditions were 0.01 ppm for⁷⁵Se and 0.1 ppm for^77mSe. When the analysis is performed through⁷⁵Se /t=120 d/, the statistical error is notably smaller because the counting time may be considerable, whereas through^77mSe/t=17.5 s/it is higher than 20%, depending on the concentration and the available neutron flux. However, the advantages of gaining time and the fact of performing the trace separation from a non radioactive material, make both procedures competitive as useful tools for the research on the function of Se in vertebrates.     

Determination of selenium in biological materials by means of RNAA and comparison of spectrophotometric and81mSe radiotracer recovery

Two methods for chemical yield measurement of Se in biological samples after radiochemical neutron activation analysis when using the⁷⁵Se nuclide are described, namely a Spectrophotometric technique and a radiotracer technique employing^81mSe. These two approaches were compared and evaluated by applying them to the analysis of Se in various certified reference materials.     

Comparison of selenium content in human hair from different individuals in different countries,by76Se(n,γ)77mSe reaction

Samples of hair from 370 subjects were analysed by neutron activation. The samples were taken from residents of nine different countries: Japan, France, Ivory Coast, Brasil, Paraguay, Canary Islands, Papua New Guinea, Italy and New Zealand. The selenium determination was made using the⁷⁶Se(n,)^77mSe reaction.It was found that the average selenium concentration in the hair of Japanese subjects, both those living in Japan and those living in foreign countries was higher (total average: 0.59±0.14 mg/kg) than those of subjects from other countries (total average: 0.42±0.13 mg/kg).Our results from the determination of the selenium concentration in the hair of individuals from different countries show significant differences between different countries, nevertheless, the selenium content in human hair was small amounts. Since this is likely due to differences in diet. This method was able to analyze quickly for many samples.     

81mSe tracer for determination of the chemical yield in radiochemical neutron activation analysis of selenium

A radiotracer method is described for measurement of the chemical yield in radiochemical neutron activation analysis of selenium using the⁷⁵Se (120 d) induced nuclide. It is based on^81mSe (57 min) radioisotopic tracer, prepared immediately before its use in the radiochemical separation procedure, by neutron irradiation of highly enriched⁸⁰Se. The recovery of selenium is calculated from the 103 keV -peak of^81mSe in the separated selenium fraction used for quantitation of⁷⁵Se. The technique is illustrated by results for biological reference materials of good accuracy and reproducibility.     

Determination of heavy metals in sewage-based fertilizer using short-lived isotopes

A fully instrumental method for the neutron activation analysis of heavy metals in sewage sludges has been developed, based on short-lived isotopes, and restricting the total experiment time to 1 hour per sample. The irradiation scheme consists of a cyclic and conventional part, the period of the cyclic irradiation being optimised for the determination of lead, using^207mPb (T=0.8 s). Gamma ray spectra from Ge(Li) detectors are stored on magnetic tape and analysed using the SAMPO programme. An IDENTIFY subroutine enables absolute determinations to be made eliminating the need for standards. Sensitivities and detection limits for 21 heavy metals have been determined and the results for several sludges are presented.     

Cyclic neutron activation analysis for determination of selenium in food samples using <Superscript>77m</Superscript>Se

Cyclic neutron activation analysis method was conducted for determination of Se in food samples. High accuracy and good precision were proved by analyzing certified reference materials (CRMs) of chicken (GBW10018), rice (GBW10010) and cabbage (GBW10014). The detection limits for the three CRMs reached 0.16, 0.66 and 1.2 ng after 6 cycles at the 161.9 keV γ-peak from ^77mSe, under a neutron flux of 9.0 × 10¹¹ n cm⁻² s⁻¹ and the conditions of 30 s irradiation, 2 s decay, 30 s counting and 2 s waiting, significantly lower than those of conventional neutron activation analysis without any cycles, which were 0.94, 3.6 and 4.3 ng, respectively.     

The separation of arsenic-77 in a carrier-free state from the parent nuclide germanium-77 by a thin-layer chromatographic method

⁷⁷As(III) and⁷⁷As(V) were separated from neutron-irradiated GeO₂ by a thin-layer chromatographic method, in which silica gel was used as adsorbent and a 2∶1 mixture of methanol and 5N HCl as developer. The Rf values of these nuclides were as follows: 0.00 for⁷⁷Ge, 0.50 for⁷⁷As(III) and 0.94 for⁷⁷As(V). The influence of As(III) carrier added before the separation was investigated on the oxidation state of⁷⁷As recoiled from the parent nuclide. The radiochemical purity of⁷⁷As thus separated was more than 99.9% and the activity due to⁷⁷As could easily be eluted with water from the adsorbent, with 93% recovery.     

Determination of selenium in food matrices by replicate sample neutron activation analysis

The replicate sample instrumental neutron activation method was optimized and used for the determination of selenium in foodstuffs. The method was reliable, yielding accurate results. Lower detections limits were obtained after each successive irradiation. Different irradiation conditions were used depending on the type of sample. For samples with higher selenium contents (meat, fish, eggs), the measured selenium in the first replicate is in all cases larger than the detection limit, but a better accuracy was obtained with a larger number of replicates (2–3 replicates). For samples with extremely low selenium contents (vegetable samples), at least seven replicates were necessary to obtain a concentration value two times larger than the detection limit.     

77Se NMR study of some organic selenium compounds formed in the selenium dioxide oxidation of ketones

⁷⁷Se NMR chemical shifts and ¹J(SeC) coupling constants were measured for nine organic selenium compounds: 4,5,6,7-tetrahydro-,4′,4′,6,6-tetramethylspiro[1,3-benzoxaselenole-2,1′-cyclohexane]-2′,4,6′-trione and closely related derivatives, bis(2-hydroxy-4,4,6,6-tetramethyl-3-oxo-1-cyclohexenyl) selenide and derivatives, and 1,5,5-trimethyl-7-selenabicyclo[2.2.1]heptane-2,3-dione. The chemicalshifts ranged from ?107 to 595 ppm from the external dimethyl selenide standard. The bridged selenabicyclic compound showed a small coupling constant (42 Hz).     

氢化物发生原子荧光法同时测定保健品中痕量锗和硒

采用微波消解样品,氢化物发生原子荧光法同时测定保健品中的锗和硒.研究了仪器条件、酸度、 KBH4浓度等对测定的影响,锗和硒的检出限为0.40和0.51 μg/L;相对标准偏差均为2.0%;回收率为77.1%～105.2%和80.0%～108.2%,已用于保健品中锗和硒的测定.     

塞曼石墨炉原子吸收法直接测定血清中的硒

采用硝酸钯为硒的基体改进剂，用塞曼效应扣除背景，对消化后的血样直接进行测定。该法的检出限为6．0ng/mL，线性范围10ng/mL－136ng/mL，回收率为94．8％－102．5％。     

Determination of selenium status using the nail biologic monitor in a canine model

Toenails and fingernails are routinely used to estimate selenium status in epidemiological studies; however, literature validating nail selenium concentration as a surrogate for critical organs is limited. In this study diets of intact male dogs were selenium supplemented at two physiological levels (3 and 6 μg/kg/day) in two different forms, selenomethionine and selenium-enriched bioformed yeast. The selenium-adequate basal diet consumed by the treatment and control groups during the 4-week run-in period and throughout the trial contained 0.3 ppm selenium. After 7 months the dogs in the two treatment groups and the control group were euthanized. Representative tissue samples from prostate, brain, liver, heart and skeletal muscle were collected, rinsed and frozen. Toenail clippings from multiple toes were also collected. Selenium was determined by neutron activation analysis using Se77m (half life = 17.4 s) at the University of Missouri Research Reactor Center. NIST SRM 1577, Bovine Liver was analyzed as a quality control. The analysts were blinded to control and treatment group assignments. As expected, tissue selenium levels increased proportionally with supplementation. A slightly greater increase in tissue selenium was observed for the purified selenomethionine compared to the bioformed yeast; however this trend was significant only for brain tissue. Toenail selenium concentrations and tissue selenium were highly correlated (p < 0.003) with Pearson coefficients of 0.759 (skeletal muscle), 0.745 (heart), 0.729 (brain), 0.723 (prostate), and 0.632 (liver). The toenail biologic monitor accurately assesses selenium status in skeletal muscle, heart, brain, prostate, and liver in the canine model.     

Determination of short-lived radionuclides in neutron-activated human head-hair samples

The Al, Na, Mn, Cl and Mg contents of human head-hair samples were determined by irradiating the samples in a thermal reactor and measuring their γ-activity by scintillation techniques. The concentration variations of these elements in hair samples originating from the same and different persons were studied.     

Kinetic aspects of the syntheses using short-lived radionuclides

“ACTIVA” is an activation analysis programme written for small computers (16 to 32 k-words) in FORTRAN-IV. Input-mode for operating commands is interactive, guided with self-explenatory questions. This enables the evaluation of gamma-spectra which could be registered under 4 different conditons (flux, geometry, etc.) with two different counting systems existing in Atominstitute. In each case another data-library with different calibration factors will be chosen and used automaticly. Programme “ACTIVA” is originally designed for gamma-spectra registered with “Loss-Free-Counting” (LFC) electronic with 2×2048 channels, but can be modified for 1024 or 4096 channels easily. Two different multichannel analysers (MCA) can be chosen for data-input: ORTEC-6240 MCA, or NOVALFC (Loss-Free-Counting). The correct energy calibration constants will also be chosen automaticly. The programme has a modular constraction and combined (linked) with overlay technique.     

Determination of selenium in animal tissue samples using radioisotope induced X-ray fluorescence

A summary of sources of background affecting gamma-ray spectrometers and methods for eliminating each are discussed, along with practical cost/benefit ratios. Background contributed by samples generally defines practical levels for system background. The practical bottom line can be obtained for relatively modest costs. A realistic bottom line is attained in underground systems when the major contributions to the background come from cosmogenically produced⁶⁸Ge and double-beta decay of⁷⁶Ge in the detector. The true bottom line is reached with isotopically enriched detectors that eliminate these two chemically inseparable radioactive impurities. Data from isotopically enriched detectors are presented.     

Determination of selenium content of animal food-stuff using photon activation analysis

Photon activation analysis has been developed to determine the selenium content. The method can be applied for continuous monitoring of the addition of selenium to animal food-stuff.     

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.