Selenium In Biological Materials Research Articles

Fast and clean determination of total selenium in biological materials by an improved oxygen flask combustion method combined with hydride generation atomic fluorescence spectrometry

A new method for fast and clean determination of Se in biological samples by hydride generation atomic fluorescence spectrometry (HG-AFS) was developed. An improved oxygen flask combustion (OFC) method based on quartz fabric cloth partially coated with glycerol was adopted for sample holding and igniting, and it showed larger sample mass ability and a co-existing metals separation effect in comparison with the conventional filer-paper based method. With the improved method, upper to 100 mg of sample could be decomposed in a 500 mL volume of oxygen under atmospheric pressure. In addition, a systematic study on the combustion behaviors of different Se species revealed that volatile SeO2, which was easily absorbed and dissociated in 10% HCl (v/v), was the only combustion product, thus, a more concise analytical procedure was realized since no additional reduction steps were needed prior to the subsequent HG-AFS determination. After method optimization, the whole sample treatment time of <40 min, the LOD of 0.0121 μg/g and the RSD (n = 6) of 0.834% were achieved, respectively. Finally, the method was evaluated by analysis of three certified standard materials and methods comparison was also conducted in four deer tissue samples analysis.

Analytical Strategy for the Determination of Selenium in Biological Materials by Inductively Coupled Plasma-Mass Spectrometry with a Dynamic Reaction Cell

ABSTRACTSelenium was determined in serum, hair, and tobacco by inductively coupled plasma-mass spectrometry using 77Se, 78Se, and 82Se. The set of standards method (SSM) and the standard addition method (SAM) were applied to calibration with and without the use of internal standards (72Ge and 103Rh). In addition, the usefulness of the dynamic reaction cell (DRC) with methane as the reaction gas was characterized. The results obtained in different conditions were evaluated in terms of precision and accuracy. It was demonstrated theoretically and experimentally that an internal standard is a potential source of systematic errors as it can be influenced multiplicatively and additively by its own interferents (independently of selenium). Furthermore, it was shown that—against common opinion—an internal standard can fail in elimination of chemical interference effects influencing selenium and in increasing of precision of selenium determinations. The DRC was shown to be effective in the elimination of additive effects, although the results obtained by both SSM and SAM with DRC were systematically positively erroneous. Finally, selenium was determined accurately in each examined sample when SAM was applied to calibration, and signals were measured either for 82Se without the use of the DRC, or for 77Se or 78Se with the use of the DRC. In addition, it has also been shown that samples should be diluted prior to analysis to the greatest acceptable extent.

Combination and optimization of the cyclic NAA modes at the Dalat research reactor for determination of selenium in biological materials using 77mSe

The combination and optimization of the cyclic modes in neutron activation analysis (NAA) at the Dalat research reactor were performed to determine short-lived nuclides. This work focused on determination of selenium in biological materials using 77mSe (T 1/2 = 17.4 s) as a case in point. The detection limit was significantly improved by a factor of 3–4 times in comparison with the conventional NAA. The precision was typically within the range of 4–6 % at the third or fourth cycle. It is a reliable technique for determination of selenium in biological materials at sub-ppm concentration levels.

Determination of selenium in biological materials by short-time neutron activation analysis using ⁷⁷ᵐSe at the Dalat research reactor

A rapid neutron activation analysis technique for determination of the concentration of selenium in biological materials using short-lived radionuclide 77mSe (half-life = 17.4 seconds) has been developed at Dalat Nuclear Research Institute (DNRI). The technique is very simple and rapid. It involves irradiation of a sample for 20 s, decay for 20 s and counting for 20 s. The accuracy of the method has been evaluated by analyzing a number of biological standard reference materials of varied selenium levels. An agreement between measured and certified values was acceptable in regarding to the deviation of the above mentioned two values within 8 percent. The result shows that the utilization of short-lived radionuclide 77mSe is more useful in comparison with long-lived radionuclide 75Se (half-life = 120 days). In addition, it is suggested that a further study for cyclic irradiations should be done in order to enhance the detection limit of the determination of the short-lived radionuclide 77mSe.

A definitive RNAA method for determination of selenium in biological samples: uncertainty evaluation and assessment of degree of accuracy

This article describes work on the development of a highly accurate RNAA method for determination of selenium in biological samples. The analytical post-irradiation procedure is based on a combination of cation-exchange and extraction chromatography with final selective and quantitative fixation of selenium on a column packed with 3,3′-diaminobenzidine (DAB) supported on Amberlite XAD4, followed by gamma-ray spectrometric measurement. The suitability and accuracy of the method was demonstrated by analysing CRMs with certified selenium content. The uncertainty budget for Se determination in standard reference material Peach Leaves NBS 1547 was estimated; the combined standard uncertainty was calculated as 1.7%. The described method fulfils all the criteria for definitive methods. It was subsequently used for determination of selenium in biological materials intended as new CRMs and proficiency test samples.

Determination of Selenium in Biological Materials Using an Ion-Selective Electrode

A method was developed for determining selenium with a self-made ion-selective electrode was developed. This electrode was made by using Ag2Se as electroactive material. Optimal working conditions and interferences were investigated. The electrode exhibits good potentiometric response for Se2− ions over the concentration range from 6 × 10−7 mol · L−1 to 1 × 10−4 mol · L−1 with a Nernstian slope of 28 ± 1 mV per decade and a detection limit of about 4.5 × 10−7 mol · L−1. It was used over six months and exhibits good selectivity and sensitivity towards Se2−. The method was applied to determine selenium in biological materials. The recovery ranges between 92% and 105.5%, and the relative standard derivation is less than 3.6% (n = 6).

Determination of selenium in biological materials by isotope dilution analysis with an octapole reaction system ICP-MS

An inductively coupled plasma quadrupole mass spectrometer (ICP-QMS) with an octapole reaction system (ORS) was used for the determination of selenium by isotope dilution analysis (IDA) in biological reference materials and serum samples from healthy subjects. The potentially interfering argon dimers (40Ar38Ar+ and 40Ar2+) at the selenium masses 78 and 80 were almost eliminated by the use of hydrogen as reaction gas. Thus, the detection limits were improved five times for 78Se and the measurement of 80Se (the main selenium isotope with an abundance of 49.61%) is now possible. An enriched 77Se solution was prepared and characterized by reverse IDA and isotope ratios measured were 78Se/77Se and 80Se/77Se. Instrumental parameters were optimised in order to obtain optimal precision and accuracy in the isotope ratio measurement of Se by ORS-ICP-QMS. The precision achieved for the isotope ratio measurements reached 0.2% (RSD for n = 5) for both ratios. Systematic errors, including detector dead time (47 ± 2 ns), mass bias effects (about 3%) and spectroscopic interferences due to the presence of bromine in the samples, were corrected. The accuracy of the measured selenium isotope ratios was improved by correcting the intensity signals of the selenium isotopes for SeH+ formation (about 3%). The proposed IDA method has been applied to the determination of Se in biological reference materials (serum, urine and tissues) and the results showed good agreement with the certified values.

Geração eletroquímica do hidreto de selênio em sistema de injeção em fluxo com detecção por espectrometria de absorção atômica com chama Ar-Glp

This paper presents a system for electrochemical hydride generation using flow-injection and atomic absorption spectrometry to determine selenium in biological materials. The electrolytic cell was constructed by assembling two reservoirs, one for the sample and the other for the electrolytic solution separated by a Nafion membrane. Each compartment had a Pt electrode. The sample and electrolyte flow-rates, acidic media, and applied current were adjusted to attain the best analytical performance and ensure the membrane lifetime. The atomisation system used a T quartz tube in an air-LPG flame. The composition of the flame, the observation height, and the argon flow rate used to carry the hydrides were critically investigated. The system allowed to perform thirty determinations per hour with a detection limit of 10 mg L-1 of Se. Relative standard deviations were in general lower than 1.5% for a solution containing 20.0 and 34.0 mg L -1 of Se in a typical sample digest. Accuracy was assessed analysing the certified materials: rice flour (NIST-1568) from National Institute of Standard and Technology and dried fish (MA-A-2), whole animal blood (A-2/1974) from the International Atomic Energy Agency.

A novel introduction system for hydride generation-inductively coupled plasma mass spectrometry: determination of selenium in biological materials

Download options Please wait... Article information DOI https://doi.org/10.1039/A909296J Article type Paper Submitted 25 Jun 1999 Accepted 24 Nov 1999 First published 03 Feb 2000 Download Citation J. Anal. At. Spectrom., 2000,15, 143-149 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions A novel introduction system for hydride generation-inductively coupled plasma mass spectrometry: determination of selenium in biological materials C. Moor, J. W. H. Lam and R. E. Sturgeon, J. Anal. At. Spectrom., 2000, 15, 143 DOI: 10.1039/A909296J To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author Christoph Moor Joseph W. H. Lam Ralph E. Sturgeon

Selenium Determination in Biological Matrices

In this study, we discuss some relevant aspects concerning the determination of selenium in biological materials with special reference to fluorometry and hydride generation atomic absorption spectroscopy (HG-AAS) techniques. The two methods may be applied without modifications to the analysis of Se in a wide spectrum of specimen types, and we describe their reliability in serum and hair analyses. Thirty-six independent control serum samples, the concentrations of which were unknown to the analyst, were analyzed in duplicate using both techniques in the Italian External Quality Assessment Scheme (EQAS). Accuracy was assessed by comparing Se values with those previously assigned by the organizers of the scheme using graphite furnace atomic absorption spectrometry (GF-AAS), which is the most frequently used technique for selenium determination in serum among the participants in the Italian EQAS. The results confirmed that fluorometry has a higher degree of accuracy than HG-AAS: the mean differences between observed and expected values were 1.5 μg/liter (95% confidence interval, -1.06 to 3.97) for fluorometry and -1.1 μg/liter (95% confidence interval, -5.05 to 2.76) for Hg-AAS. We also report some results obtained for the determination of Se in hair. Since a critical step in hair preparation is the pretreatment for removal of external contamination, we compared six different washing procedures. In general, Se is poorly leached from hair, but the efficiency of removal differed with the substance used, ranging from 0 to 13% of the original content. A nonionic detergent like Triton X-100 offers the advantage of safe working conditions and a substantial reduction in costs compared with organic solvents. Lastly, in a consistent group (n = 131) of women, Se in hair was found to be strongly reduced by the use of dye (389.9 ng/g vs 498.7 ng/g, P < 0.001). We recommend recording information on cosmetic treatments when hair is collected to evaluate Se reference values in epidemiological studies.

High-Performance Liquid Chromatographic–Fluorescence Determination of Traces of Selenium in Biological Materials

An improved method for the determination of selenium in biological materials has been developed. This work both extends and validates the procedure of Vézina and Bleau (J. Chromatog.426, 385–391, 1988) which is based on high-performance liquid chromatographic determination of the fluorophore formed by reaction of Se(IV) with 2,3-diaminonaphthalene. The mass detection limit is 48 pg selenium (3σ) and the concentration detection limits are 48 parts per trillion in biological fluids and 120 to 480 parts per trillion in dried biological materials. The linear dynamic range of the method has been extended up to approximately 800 ng. Relative standard deviations of 9.4 to 2.7% were observed in repeated analyses of standards in the range of 0.5 to 500 ng. The proposed method was validated with respect to 23 biological reference materials spanning an 1800-fold range of selenium concentrations and was found to be free of significant constant or proportional biases despite greatly different matrix compositions. This method offers an unsurpassed combination of sensitivity, accuracy, linear dynamic range, and freedom from matrix interferences and may be considered a reference method for the reliable determination of selenium in biological materials.

Determination of selenium in biological materials by neutron activation analysis

Radiochemical neutron activation analysis for the determination of Se in biological samples is described. Post-irradiation chemical separation permits the good separation efficiency of elemental selenium (95±3%) immediately after thermal neutron activation. Biological materials were decomposed by wet combustion and then elemental selenium was collected after adding cysteine to the resulting solution.

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 employing81mSe. These two approaches were compared and evaluated by applying them to the analysis of Se in various certified reference materials.

Rapid one-step derivatization of Se(VI) to a piazselenol for the spectrofluorimetric determination of selenium in biological material

A spectrofluorimetric method for the determination of total selenium in biological samples has been developed. After oxidative destruction, the sample is reacted with a mixture of bromide and 2,3-diamino-1,4-dibromonaphthalene (Br 2-DAN) without pH adjustment. Selenium(VI) is rapidly reduced by bromide to Se(IV) which then forms 4,7-dibromo-5,6-benzopiazselenol (Br 2-DAN-Se). The conversion of Se(VI) to Br 2-DAN-Se is completed in 6 min at 100°C. The piazselenol is extracted to cyclohexane and the fluorescence measured at 577 nm with excitation at 518 nm. The procedure has been validated by determinations on reference materials with selenium concentrations ranging from 4 to 1460 ng g −1. The advantages of the method are the fast reduction of Se(VI) by hydrobromic acid and the properties of Br 2-DAN, which permit the piazselenol formation to be carried out in a strongly acidic medium and at high temperature. The limit of detection is 0.6 ng g −1 as estimated by three times the standard deviation of the blank determination ( n = 7). The rate of reduction of Se(VI) to Se(IV) in hydrobromic acid was investigated as a function of concentration and temperature. The new kinetic data together with previous kinetic and equilibrium data for the piazselenol formation were used to model and optimize the simultaneous reduction-derivatization procedure.

Isotope Dilution Analysis of Selenium in Biological Materials by Nitrogen Microwave-Induced Plasma Mass Spectrometry

Nitrogen microwave-induced plasma mass spectrometry was applied to isotope dilution analysis of selenium in biological matrices. The precision of isotope ratio ( 80 Se/ 78 Se) measurements of a 100 ng/mL standard solution was 0.5% under practical analysis conditions and could be after lowered by increasing the integration time. spectroscopic interference at m/z=80 arising from SO 3 + was observed, but the extent was not so much as to cause a serious problem at the sulfur level normally found in biological materials. Isotopic ratios in digested clinical specimens pod well with those in the standard solution, indicating no other spectroscopic interferences on selenium isotopes in real samples. The proposed method was successfully applied to the analysis of selenium in biological reference materials. The results showed good agreement with the certified values

Determination of selenium in biological matrices using a kinetic catalytic method.

A simple and sensitive catalytic spectrophotometric method was developed for the determination of selenium in biological matrices. The method is based on the catalytic effect of selenium on the reaction of Methylene Blue (MB) with sodium sulfide. For a given reaction between MB and sodium sulfide, the change in the MB absorbance with time was monitored, then the time (t) required for completion of the reaction was determined, and t-1 was calculated. A plot of t-1 versus selenium concentration constituted the calibration graph, which was linear in the range 2.5-30 ng ml-1 selenium. In this study, experimental parameters and the effect of interferences on determinations of selenium were examined. Tetramethylammonium hydroxide digestion was applied to blood, hair and urine samples; it was found to give the best results for urine. Then the catalytic method was applied to urine samples (84.9% recovery).

Modified electrical heating system for hydride generation atomic absorption spectrometry and elaboration of a digestion method for the determination of arsenic and selenium in biological materials

A modified electrical heating system for hydride generation atomic absorption spectrometry has been designed. The heating block permits a rapid and convenient change of the quartz tube in order to clean and condition its surface. Frequent conditioning guarantees high and constant measurement sensitivity. Further, an inexpensive and simple microwave digestion procedure has been developed. The methods were tested by analysing reference materials and proved to be appropriate for trace concentrations of arsenic and selenium.

Selection of reference methods for the determination of selenium in biological materials

Over the period 1985–1989 the European Community Bureau of Reference (BCR) has certified 7 biological reference materials for selenium with concentrations ranging from 0.03 to 10 mg/kg. Certification analyses were carried out by the most experienced laboratories in the Member States, using Fluorimetry, Hydride formation, combined with ICP or AAS, Electrothermal AAS with or without Zeeman-background correction, Instrumental or radiochemical NAA. Results from these exercises are available in a form suitable for estimating the experimental precision of the various methods as a function of concentration. With the same number of replicates for all analyses the logarithm of the observed standard deviations have constant variance, independent of concentration; for each method the absolute and relative standard deviations can therefore be estimated by means of non-linear regression. Analytical bias was monitored plotting results and their estimated standard deviations from individual laboratories versus certified confidence intervals. For concentrations of Se <0.3 mg/kg fluorimetry was selected as a reference method; above this level INAA is recommended; both are capable of producing unbiased results.

Isotopic determination of selenium in biological materials with inductively coupled plasma mass spectrometry.

A method for the isotopic determination of selenium in biological matrices is described. The method is based on hydride generation inductively coupled plasma mass spectrometry (ICP-MS). The development is specifically related to the requirements of stable isotope tracer studies in human subjects. The method is based on isotope dilution using 82Se as the in vitro spike and can quantify the 74Se and 77Se contents of samples. It involves wet oxidation (HNO3 - H2O2 or HNO3 - HClO4) of the 82Se-spiked matrix, reduction to selenite by boiling with HCl followed by measurement of the isotope ratios (82Se/77Se and 74Se/77Se) in the gas stream (H2Se) generated from on-line reduction of the sample selenite with NaBH4. Compared with the isotopic signal resulting from a selenite solution containing 5 ng ml-1 of Se, the total sample blank contributions at m/z = 74, 77 and 82 were less than 5% of the respective isotope signal. Worst-case absolute detection limits were 0.2-0.9 ng of Se, depending on the isotope used. Ion beam intensity ratios were measured with an over-all precision [relative standard deviation (RSD)] of 1% for both isotope pairs. Measured ratios (MRa/b) were stable during a given day's operation within the expected precision of the measurements but varied for different days. The magnitude of MRa/b was generally independent of the nature of the matrix. Highly linear relationships were found between ion beam intensity ratios (MRa/b) and the corresponding true isotope ratios for calibration solutions whose isotope ratios had been altered by as much as one order of magnitude.(ABSTRACT TRUNCATED AT 250 WORDS)

Radiochemical separation of7 5Se with o-phenylenediamine for instrumental neutron activation analysis of selenium in biological materials

A new method of radiochemical separation for determination of selenium in biological materials has been developed. The method is based on the reaction of tetravalent selenium with the amino groups of aromatic ortho-diamines resulting in selenodiazoles, which can be easily extracted with organic solvents. The biological samples were irradiated in a reactor, mineralized with nitric and perchloric acids and MgCl2. Selenium was transformed to teravalent form with hydrochloric acid and the resulting bezoselenodiazole formed in the reaction with o-phenylenediamine was extracted with toluene. The radioactivity of selenium7 5Se was measured with a well-type NaI(Tl) scientillation detector. The accuracy of the method was verified by determining selenium levels in SRM NBS. The detection limit of the method was found to be 0.5 ng Se. The comparison of selenium levels in human blood determined by HG-AAS. non-destructive NAA and the described method is presented.