Selenium hydride
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This work describes the intricacies of the determination of the trimethylselenonium ion (TMSe) in human urine via high-performance liquid chromatography-hydride generation-atomic fluorescence spectrometry (HPLC-HG-AFS). By definition, this technique requires that the separated TMSe can be online converted into a volatile compound. Literature data for the determination of TMSe via the hydride generation technique are contradictory; i.e., some authors claim that direct formation of volatile compounds is possible under reduction with NaBH4, whereas others reported that a digestion step is mandatory prior to conversion. We studied and optimized the conditions for online conversion by varying the mobile phase composition (pyridine, phosphate, and acetate), testing different reaction coils, and optimizing the hydride generation conditions, although technically no hydride (H2Se) is formed but a dimethylselenide (DMSe). The optimized conditions were used for the analysis of 64 urine samples of 16 (unexposed) volunteers and the determination of low amounts of TMSe (LOD = 0.2 ng mL-1). Total (specific gravity-corrected) selenium concentrations in the urine samples ranged from 7.9 ± 0.7 to 29.7 ± 5.0 ng mL-1 for individual volunteers. Four volunteers were characterized as TMSe producers (hINMT genotype GA) and 12 were non-producers (hINMT genotype GG). Urine of TMSe producers contained 2.5 ± 1.7 ng mL-1 of TMSe, compared to 0.2 ± 0.2 ng mL-1 for non-producers.
- MeSH
- fluorescenční spektrometrie MeSH
- lidé MeSH
- selen * moč MeSH
- sloučeniny selenu * MeSH
- vysokoúčinná kapalinová chromatografie metody MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
The aim of this study was to develop a method of Se and As determination in drinking water by electrochemical hydride generation coupled with AAS. Three types of electrolytic cells were constructed and optimized for the determination. Two cells (thin-layer and tubular) were finally chosen for their low inner volume and a high hydride generation efficiency (ca. 90 %). The limits of detection of As(III) and Se(IV) were 0.07 and 0.37 ng ml–1, respectively. The accuracy of the method was verified using reference materials.
Several mineralization methods for the determination of selenium using hydride generation optical emission spectrometry with inductively coupled plasma in biological samples (whole egg powder and pork liver) were compared using the analysis of means (ANOM) method. This statistical tool is suitable for graphical representation of testing on simple comparative experiments. The results yielded by ANOM are identical with those obtained with the commonly used analysis of variance (ANOVA) method; however, the graphical output of ANOM is more illustrative in comparison to ANOVA. Both methods indicated a significant discrepancy between the results obtained using muffle furnace ashing mineralization and the results provided by other mineralization methods. This is probably due to the loss of volatile selenium compounds during the decomposition of organic matter.
Atomization of hydrides and their methylated analogues in a dielectric barrier discharge (DBD) plasma atomizer was investigated. Selected ion flow tube mass spectrometry (SIFT-MS) was chosen as a detector being capable of selective detection of non-atomized original volatile species allowing thus direct quantification of atomization efficiency. Selenium hydride (SeH2) and three volatile arsenic species, namely arsenic hydride (AsH3), monomethylarsane (CH3AsH2) and dimethylarsane ((CH3)2AsH), were selected as model analytes. The mechanistic study performed contributes to understanding of the atomization processes in atomic absorption spectrometry (AAS). The presented results are compatible with a complete atomization of arsenic hydride as well as its methylated analogues and with atomization efficiency of SeH2 below 80%. Using AsH3 as a model analyte and a combination of AAS and SIFT-MS detectors has revealed that the hydride is not atomized, but decomposed in the DBD atomizer in absence of hydrogen fraction in the carrier gas. Apart from investigation of analyte atomization, the SIFT-MS detector is capable of quantitative determination of water vapor content being either transported to, or produced in the atomizer. This information is crucial especially in the case of the low-power/temperature DBD atomizer since its performance is sensitive to the amount of water vapor introduced into the plasma.
Vonkajšie faktory životného prostredia, fajčenie a stres podnecujú v našom organizme tvorbu veľmi reaktívnych voľných častíc – radikálov. V prípade nedostatku vhodných obranných mechanizmov v organizme, tieto reaktívne častice vytvárajú v tele prostredie pre vznik zápalových chorôb. Ľudské telo má vlastné obranné mechanizmy chrániace organizmus pred voľnými radikálmi. Z tohto hľadiska nadobúdajú zvýšený význam najmä antioxidanty, čo sú látky schopné neutralizovať voľné radikály. Jedným z kľúčových antioxidantov je práve nutričný prvok selén, význam ktorého už bol potvrdený množstvom rôznych štúdií 1). Cieľom práce bolo vypracovať a optimalizovať pracovné podmienky pri identifikácii a stanovení selénu v krvnej plazme u pacientov trpiacich na zápalové kožné ochorenie, ktorým je atopická dermatitída. Stanovené hodnoty selénu u pacientov s uvedeným ochorením boli porovnané s hodnotami selénu, ktoré boli stanovené u skupiny zdravých jedincov. Cieľom práce bolo taktiež vyhodnotiť súvis medzi zníženou hladinou selénu v organizme a atopickou dermatitídou ako aj sledovať vplyv užívania prípravku s obsahom selénu na priebeh ochorenia. Merací postup bol verifikovaný porovnaním výsledkov obsahu selénu získaných novšou elektrochemickou analytickou metódou – galvanostatickou rozpúšťacou chronopotenciometriou (SCP) s výsledkami získanými komparačnou metódou – atomovou absorpčnou spektrometriou s generovaním hydridov (HGAAS).
In the human organism, the external factors of the environment, smoking and stress provoke the production of very reactive free particles – radicals. In the case of deficiency of suitable protective mechanisms in the organism, these reactive particles produce the conditions for the development of inflammatory diseases in the body. The human body possesses protective mechanisms of its own to defend the organisms against free radicals. From this viewpoint, particularly antioxidants, i.e. substances capable to neutralize free radicals, are of increased importance. One of the antioxidants of key importance is the nutritional element selenium, the importance of which has already been confirmed in a number of different studies 1). The present paper aimed to elaborate and optimize the working conditions in the identification and determination of selenium in blood plasma in patients suffering from atopic dermatitis, an inflammatory skin disease. The selenium values found in patients suffering from the above-mentioned disease were compared with the selenium values determined in a group of healthy subjects. The paper also aimed to evaluate the connection between a decreased selenium level and the organism and atopic dermatitis as well as to examine the influence of the administration of a preparation containing selenium upon the course of the disease. The procedure of measurement was verified by comparing the results of selenium content obtained by a more recent electrochemical analytical method – galvanostatic solution chronopotentiometry (SCP) – with the results obtained by a comparative method – hydrid generation atomic absorption spectrophotometry (HGAAS).
The response of giant reed (Arundo donax L.) to selenium (Se), added as selenate, was studied. The development, stress response, uptake, translocation, and accumulation of Se were documented in three giant reed ecotypes STM (Hungary), BL (USA), and ESP (Spain), representing different climatic zones. Plantlets regenerated from sterile tissue cultures were grown under greenhouse conditions in sand supplemented with 0, 2.5, 5, and 10 mg Se kg-1 added as sodium selenate. Total Se content was measured in different plant parts using hydride generation atomic fluorescence spectroscopy. All plants developed normally in the 0-5.0 mg Se kg-1 concentration range regardless of ecotype, but no growth occurred at 10.0 mg Se kg-1. There were no signs of chlorosis or necrosis, and the photosynthetic machinery was not affected as evidenced by no marked differences in the structure of thylakoid membranes. There was no change in the maximum quantum yield of photosystem II (Fv/Fm ratio) in the three ecotypes under Se stress, except for a significant negative effect in the ESP ecotype in the 5.0 mg Se kg-1 treatment. Glutathione peroxidase (GPx) activity increased as the Se concentration increased in the growth medium. GPx activity was higher in the shoot system than the root system in all Se treatments. All ecotypes showed great capacity of take up, translocate and accumulate selenium in their stem and leaf. Relative Se accumulation is best described as leaf ˃˃ stem ˃ root. The ESP ecotype accumulated 1783 μg g-1 in leaf, followed by BL with 1769 μg g-1, and STM with 1606 μg g-1 in the 5.0 mg Se kg-1 treatment. All ecotypes showed high values of translocation and bioaccumulation factors, particularly the ESP ecotype (10.1 and 689, respectively, at the highest tolerated Se supplementation level). Based on these findings, Arundo donax has been identified as the first monocot hyperaccumulator of selenium, because Se concentration in the leaves of all three ecotypes, and also in the stem of the ESP ecotype, is higher than 0.1% (dry weight basis) under the conditions tested. Tolerance up to 5.0 mg Se kg-1 and the Se hyperaccumulation capacity make giant reed a promising tool for Se phytoremediation.
The aims of this study were to test analytical procedures for the determination of Cd, Cu, Mn, Pb, Se and Zn in breast milk and to establish optimum sampling conditions for monitoring purposes. Two population groups were analysed: (1) Seven women from Prague whose breast milk was sampled on days 1, 2, 3, 4, 10, 20 and 30 after delivery; (2) 200 women from four (two industrial and two rural) regions whose breast milk was sampled at defined intervals. All samples were mineralised in a microwave oven in the mixture of HNO3 + H2O2 and analysed by atomic absorption spectrometry. Conditions for the measurement of the elements under study (i.e. those for the electrothermal atomisation for Cd, Mn and Pb, flame technique for Cu and Zn, and hydride generation technique for Se) were optimized. Using optimized parameters the analysis was performed and the following conclusion has been made: the concentrations of zinc and manganese decreased very sharply over the first days, that of copper slightly increased within the first two days and then slightly decreased, that of selenium did not change significantly. Partial “stabilisation” was achieved after the second decade. No correlation among the elements was found. A significant difference between whole and skim milk was only found for selenium (26% rel. higher in whole milk). The majority concentrations of cadmium and lead were below the detection limit of the method (0.3 µg.l-1 and 8.2 µg.l-1, respectively, as calculated for the original sample). To provide biological monitoring, the maintenance of sampling conditions and especially the time of sampling is crucial.
... Těkavé hydridy, pseudoatomy -- 2. Btruktura molekul -- 55. Chemická vazba -- 1. ... ... Selen, Selenium, tellur. Tellurium 303 -- 136. Biologie a toxikologie selenu a telluru 303 -- 137. ...
685 s.
Zevrubná učebnice chemie vysokých škol postupuje od obecného (atomy, molekuly, druhy vazeb) k látce specifické (halogeny, roztoky elektrolytů, koloidy, polokovy, kovy).
- Konspekt
- Chemie. Mineralogické vědy
- NLK Obory
- chemie, klinická chemie
