Loss Of Selenium Research Articles

A flow injection-flame-atomic absorption spectrometry system for the determination of the real stoichiometry of small CuInSe2 semiconductor crystals

A method for the rapid determination of the real stoichiometry of small CuInSe2 semiconductor crystals is presented. The powdered crystal samples have been weighed and acid dissolved in a closed dissolution system connected to a FI manifold for flame atomic absorption spectrometry (AAS) determination. The accuracy has been assessed by comparing the results obtained with those by conventional AAS, and by analyzing CuInSe2 polycrystals of known stoichiometry. The results obtained with the proposed method are in a good agreement with the expected values. The method allows the dissolution of the crystals without any detectable loss of selenium and has been applied to the analysis of small samples of CuInSe2 monocrystals as a method for routine monitoring during the development of synthesis methods and in homogeneity studies of the crystal ingots.

Uptake, distribution, and turnover rates of selenium in barley.

The present communication elucidates initially the topographic distribution of selenium in barley grains. Then by the fluorimetric method the uptake of selenium (selenite) in 8-16 d old germinating barley was estimated. Finally by means of 75Se the anabolic and catabolic rates (turnover) of 75Se (selenite) was compared. The distribution of selenium in barley was evaluated after micro-dissection of barley grains. In dried grains the highest concentration was found in husk and pericarp with about 0.6 ppm Se. Then followed Scutellum with 0.4 and 0.3 ppm in embryon. The aleurone layer, embryonic leaves, and initial root did only have 0.2 ppm Se. In order to know more about the uptake and distribution of selenium in 8-d-old barley, the plants were cultivated for a further 8 d in the culture medium with variation in selenite concentration. In roots and leaves, the uptake did not arrive at saturation during the period studied since the dose-response curve increased up to 0.34 mM selenite in the medium, whereas the selenium levels were about 200 ppm in roots and 30 ppm in leaves. However, the uptake was linear, with concentration during 8 d of cultivation up to 0.84 microM selenite for grain and stem. At higher concentrations the dose-response curve diminished its slope. At 0.34 mM selenite the concentration in grain increased to 6.87 ppm and in the stem to 8.13 ppm. The uptake, distribution, and catabolic rate of selenium components in germinating barley were further evaluated by exposing the plants to 0.0492 microCi 75Se (12.6 microM selenite) for up to 4 d. Then the plants were moved to a selenium deficient medium for further 4 d. Then finally the medium was supplemented with high doses of cold selenite (0.126 mM selenite) for further 4 d. The first third period made it possible to estimate the rate of uptake. It was highest in roots (313 fmol/h/mg dw), i.e., about 10 times those of grains, stems, and leaves. The intermediate period where the barley was transferred to a selenium deficient medium made it possible to estimate the kinetics and eventual sparing mechanisms. The selenium losses were highest for leaves (39%), then followed by roots and stems (22 and 25%, respectively). The losses were lowest in grain with 9% Se losses. The losses were three times more pronounced during the first day than in the following 3 d. These data may argue that the selenium is distributed into different pools and that sparing mechanisms may be in function.(ABSTRACT TRUNCATED AT 400 WORDS)

Selenium renal homeostasis is impaired in patients receiving long-term total parenteral nutrition.

Selenium deficiency has been reported previously in patients receiving long-term total parenteral nutrition (TPN) without selenium supplementation in their solutions. The recommended dietary allowance for selenium is 0.87 microgram/kg, of which 80% is absorbed. We studied 28 adult long-term TPN patients aged 21 to 79 years (mean, 51.2 +/- 3.0 years) who have received TPN for 8.3 +/- 4.4 years. They receive 40 to 60 micrograms of selenium daily in their TPN solution. Twenty-one (75%) of 28 patients had low serum selenium levels. Of the patients with low serum selenium levels, 15 (73%) had elevated urinary selenium losses. However, no significant correlation between serum or urine selenium levels and glomerular filtration rate (measured by indium-111-diethylenetriamine pentaacetic acid clearance) or renal tubular function was observed. We conclude that the previously described renal homeostatic mechanism for selenium conservation may be significantly impaired in patients receiving long-term TPN. Such patients may require much larger doses of selenium than previously recommended. Therefore, patients receiving long-term TPN should have their serum selenium level monitored even though they receive daily selenium supplementation.

Loss of selenium in water samples at natural levels during storage

Selenium losses in river, ground, snow-melt and tap water samples, and the recovery of selenite, selenate and selenomethionine added to purified water have been studied. In 1-litre high-density polyethylene bottles, tap, river and snow-melt water samples (at Se concentrations of 44.5–138 ng/l) could be stored at 4 °C for up to 15 days without Se losses. In similar samples stored at room temperature Se losses of 13–25% after 15 days were found, except for groundwater, which showed no Se losses during storage for 13 months at room temperature or at 4 °C. Selenite and selenate added to purified water were recovered without losses after 15 days at 4 °C, while 7.5% of selenomethionine was lost. The stability of different chemical forms of Se during storage followed the order: selenate > selenomethionine > selenite. It is recommended that unacidified water samples should not be kept in polyethylene bottles at room temperature for more than 1 week, nor stored at 4 °C for more than 2 weeks, before analysis for Se.

Studies on the breakdown of organoselenium compounds in a hydrobromic acid–bromine digestion system

The chemical role played by bromine in HBr solution was investigated in the breakdown of both the trimethylselenonium ion and selenomethionine. Hydride generation and gas chromatography, both coupled with atomic fluorescence detection, polarography, and 1H and 77Se nuclear magnetic resonance spectrometry, were employed in order to collect information on the intermediate and final selenium compounds. Trimethylselenonium and selenomethionine were quantitatively converted into inorganic SeIV in hot concentrated HBr, but only in the presence of a large excess of bromine with respect to organoselenium. In the absence of additional bromine and under a stream of inert gas, the digestion of trimethylselenonium resulted in a 95% loss of selenium from the solution. Dimethyl diselenide and dimethyl selenide were detected in the headspace gases of the digestion apparatus. Under the same conditions, selenomethionine gave a result of about 70% of selenium caught in the solution. In this instance experimental evidence indicated that the major selenium component in the headspace gases of the digestion apparatus was methaneselenol. The roles played by bromine and HBr in the conversion of organoselenium into inorganic SeIV were identified as (i) the oxidative addition of bromine to divalent selenium to form bromoselenonium intermediates and (ii) the dealkylation of selenonium compounds by the bromide ion.

Selenium losses in 10 burned patients

To determine the selenium (Se) losses and balances, 10 patients with burns of 32 ± 9% (mean ± SD) of total body surface and aged 36 ± 9 years were studied from D1 (first post-injury) unitl D7. Cutaneous losses were extracted from the textiles surrounding the patients. Serum and urine were collected until D20.Exudative losses of nitrogen decreased progressively (mean 8.7 ± 3.8 g/24H). Se was detectable in wound seepage only during excision-grafting: mean operative loss was 342 ± 191 μg. Mean urinary Se excretion was 41 ± 13 μg/24H. Operative cutaneous losses led to some negative balances. Serum Se and glutathione peroxydase (GSHPx) were depressed until D20. Serum Se was related to N intake (p < 0.001).The decreased Se and GSHPx levels reflect a deficiency state, which measured losses did not explain, but limitations of the measurement methods prevented detection of Se cutaneous losses ⩽100 μg/24H.

Characterizations of electrodeposited CuInSe 2 thin films: Structure, deposition and formation mechanisms

Effects of annealing conditions on the structure characteristics of electrodeposited CuInSe 2 thin films were investigated by using X-ray diffractometry. For copper-rich thin films, the preferred orientation factor f(112) at (112) direction and the effective grain size increased as the annealing temperature and time increased. Less profound effects were observed for the indium-rich films. The annealed copper- rich films are predominantly chalcopyrite and highly conductive, while annealed indium-rich films are mainly sphalerite and very resistive. A structural transition from chalcopyrite to sphalerite was observed for the first time on the electrodeposited CuInSe 2 as the composition of the thin films varied from copper rich to indium rich. The presence of oxygen during annealing was found detrimental to the films, resulting in the formation of indium oxides due to partial oxidation of indium and associated loss of selenium and a large increase in the film conductivity. Effects of various chemical treatments on film composition, morphology, and corresponding structural change were also studied to elucidate the thin film deposition and formation mechanisms. The results showed that the as-deposited films are made of CuInSe 2, Cu x Se, In y Se, and seledium. Depending on the sequence of annealing and chemical treatments, the resulting thin films could be either copper- rich chalcopyrites or indium-rich sphalerites.

Improved Selenium Recovery from Tissue with Modified Sample Decomposition

The present paper describes a simple modification of a recently reported decomposition method for determination of selenium in biological tissue by hydride generation atomic absorption. The modified method yielded slightly higher selenium recoveries (3-4%) for selected reference tissues and fish tissue spiked with selenomethionine. Radiotracer experiments indicated that the addition of a small volume of hydrochloric acid to the wet digestate mixture reduced slight losses of selenium as the sample initially went to dryness before ashing. With the modified method, selenium spiked as selenomethionine behaved more like the selenium in reference tissues than did the inorganic spike forms when this digestion modification was used.

The renal excretion of selenium

The excretion of selenium in urine was determined in West German healthy volunteers. Women excrete 17.7 +/- 4.2 micrograms Se/d and men 19.0 +/- 9.0 micrograms Se/d. The daily selenium excretion per gram creatinine is 13.5 +/- 3.8 micrograms Se/g crea for women and 9.8 +/- 3.3 micrograms Se/g crea for men. The clearance of selenium from the plasma is calculated with 0.18 mL/min. The selenium excretion per day is positively correlated with the 24 h excretion of urea and creatinine. The correlation of the selenium excretion with the urea excretion is most probably owing to the fact that the selenium intake of West Germans is linked primarily to foods with high protein contents. That the selenium excretion is directly correlated with the creatinine excretion is an indicator that the muscle, which accounts for nearly 50% of the whole body selenium in West German adults, influences the selenium excretion in urine. The positive correlation of the selenium excretion with the potassium excretion also indicates that the muscle mass contributes significantly to the selenium excretion in urine. Another indicator that the selenium excretion is influenced by the muscle is that after intensive muscular activity (running), selenium excretion is enhanced. The 24 h selenium excretion is dependent on the glomerular filtration rate of the kidney characterized by the creatinine clearance. This result is important, because if the selenium excretion is used as parameter for the selenium status of humans, the kidney function should be known. This is a limitation for the use of the urinary selenium excretion as parameter for the selenium status. This is especially important for patients whose glomerular filtration rate is low. The 24 h selenium excretion is further influenced by the 24 h urine volume. Selenium losses via urine may be concomitant with protein losses in urine.

Selenium accumulation and elimination in mallards

Selenium accumulation and loss were measured in adult mallards (Anas platyrhynchos) fed selenomethionine during two experiments. In Experiment 1, both sexes were fed a diet containing 10 ppm selenium for 6 weeks, followed by 6 weeks on untreated feed. Selenium accumulation in liver and muscle of females was described by C = A(1-e-bt). Concentrations of selenium were predicted to reach 95% of equilibrium faster in liver (7.8 days) than in muscle (81 days). The loss of selenium from liver and muscle of females was described by the exponential loss rate equation: C = Ae-bt, with half-times of 18.7 and 30.1 days, respectively. Males reached similar levels of selenium in liver and breast muscle as females and declined to similar levels once selenium treatment ended. In Experiment 2, females were fed increasing levels of selenium until some died. Survivors were switched to an untreated diet and selenium was measured in blood, liver, and breast muscle over 64 days. The same equation as in Experiment 1, C = Ae-bt, was used to describe the loss of selenium from blood and muscle. Half-times were 9.8 and 23.9 days, respectively. For liver, the equation C = A1e-b1t + A2e-b2t was used. Selenium initially decreased in liver by one-half in 3.3 days, with subsequent half-times of 3.9, 6.0, and 45.1 days.

Stability and behaviour of selenium in total parenteral nutrition solutions

Selenium stability in amino acid/dextrose/electrolytes/ascorbic acid/trace elements was evaluated by a specific and sensitive fluorimetric method of selenium(IV) determination. Ascorbic acid particularly with copper(II) ions, reduced selenium(IV) in selenium metal (Se). Cysteine present in amino acids solution induces complexation with selenium. The complex has been identified by high-performance liquid chromatography when cysteine and selenite are mixed in 4 1 molar ratio. The complex is releasing cystine and selenium(II). These reactions are responsible for the complete loss of selenium(IV) in total parenteral nutrition solutions.

Selenium losses on cooking Greek foods

SummaryThe effect of various cooking practices (frying, grilling, boiling and canning) on the selenium content of selected food items has been determined. All foods examined upon cooking lost selenium and, in general, the harsher the cooking conditions the more selenium was lost. Fish lost 36–46%, meats 13–41%, cereals 20–30%, vegetables 12–37%, pulses and cereal products 5–10% selenium. It is estimated that Greeks receive 110 and c. 95 μg Se/day based on raw, and cooked plus uncooked foods, respectively. Cooking does not make a large difference to the daily selenium intake of Greeks because of their large consumption of bread.

Selenium Content of Chicken Meat as Affected by Cooking

ABSTRACTTwelve dressed chickens of the same flock were quartered and prepared by four cooking treatments: microwaving, conventional oven cooking, broiling, and panfrying. The mean value of selenium (fluorometic method) in raw chicken was 0.38 μg/g dry weight, with no significant differences between white and dark meat. There was insignificant loss of selenium due to cooking. Cooked chicken breast had a significantly higher level of dialysable selenium compounds (MW &lt; 2000 daltons) than raw chicken.

Some new 3-substituted 3-hydroxyselenetanes and their loss of selenium

Some new 3-substituted 3-hydroxyselenetanes and their loss of selenium

Comparison of recoveries of inogranic and organic incorporated75Se by four mineralization methods of biological material

The recovery of selenium75Se added as selenite to human blood and to mixed food, and the recovery of biologically incorporated75Se from different rat tissues were determined by using four mineralization methods. The recoveries of75Se after dry ashing /HNO3, Mg/NO3/2/ and after three wet digestion methods — 1. HNO3, HClO4 2. HNO3, HClO4, H2SO4 3. HNO3, HClO4, MgCl2 were as follows: 50–106%, 96–99%, 92–99% and 97–100%, resp. Losses of75Se in wet digestion /HNO3, HClO4/ were observed at the end of the procedure, when an excess of acids was evaporated. The addition of MgCl2 to the digestion mixture prevented the escape of75Se and thus permitted the total evaporation of the digest without any loss of selenium.

The application of NAA with irradiation at reduced temperature for the study of element losses during pretreatment of biological samples

We have developed an irradiation facility by means of which samples can be irradiated near the core edge of the reactor BER II in liquid nitrogen at a thermal-neutron flux of 1.5.1013 n·cm−2·s−1 for a maximum of 14 days. We present the technique of neutron activation analysis in which biological samples enclosed in thin-walled quartz ampoules are irradiated and measured directly without pretreatment. Using this method, losses of iron, zinc and selenium during pretreatment procedures (freeze-drying and oven-drying at 30, 60, and 90°C) for the analysis of plasma, erythrocytes and liver were studied.

Determination of selenium with solid sampling and direct Zeeman-AAS

Addition of fine grained elemental nickel stabilizes selenium in inorganic solid samples, so that no selenium losses can be detected up to 2,000 °C pretreatment temperature. The specific absorption signals of selenium are significantly broadened and delayed. Interferences by sulphur are overcome by this effect, because the sulphur compounds appear in the gas phase before selenium. For organic materials, however, the addition of nickel as matrix modifier for solid sampling ZAAS fails.

Effect of heat treatment on electrodeposited CuInSe 2 films

Thin films of CuInSe 2 prepared by an electrodeposition method have been heat treated at temperatures up to about 450°C. The heat treatments were done in an evacuated environment. After the heat treatment, the samples were examined by electron probe microanalysis for composition and by X-ray diffraction for determination of crystalline quality. The results obtained showed that the quality of the films was improved by the heat treatment. From the compositional results, it was found that there was a loss of selenium during the heat treatment.

Determination of selenium in silver plating solution by automated hydride generation-ICP-AES.

Determination of selenium in silver plating solution was studied by automated hydride generation-ICP-AES (HG-ICP-AES). The sample was decomposed with nitric and sulfuric acids. Loss of selenium by volatilization during decomposition was not observed. Selenium was seperated prior to the analysis by distillation as the bromide in order to eliminate the effect of coexisting elements. Both selenium(IV) and (VI) were quantitatively recovered by this distillation. In the plating solution, there were large amounts of coexisting elements, but these elements did not interferece with the distillation of selenium. Selenium in the distillate was determined by HG-ICP-AES. This method was applied to the determination of selenium in actual silver plating solutions. The recoveries of this method were 96104% and the analytical results were in good agreement with those from the spectrophotometric method. The relative standard deviations were 1.54.3%.

Direct electrothermal atomisation atomic absorption spectrometric determination of selenium in whole blood and serum with continuum-source background correction

In the determination of selenium, the well documented spectral interferences originating from phosphates and iron present in the biological fluids are eliminated by the addition of platinum. Pre-atomisation losses of selenium are avoided in the presence of nickel (15 µg) and platinum (60–120 µg). Using a pyrolytically coated tube together with off the wall atomisation, the sensitivity in terms of characteristic mass is 60 pg (0.0044 A s), while the detection limit (twice the base-line noise) is 3 ng ml–1. Within-run precision is better than 8% while between-run relative standard deviation is less than 10%. Validation of the developed method has been made by using a certified reference material and by comparing the results with hydride generation and neutron activation analysis. The proposed method is rapid, accurate and precise and can be used for analysing up to 50 serum samples per day.