ETAAS method for the determination of Cd, Cr, Cu, Mn and Se in blood fractions and whole blood

An electrothermal atomic absorption method (ETAAS) for the direct determination of trace elements (Cd, Cr, Cu, Mn, Se) both in blood fractions (erythrocytes, plasma and lymphocytes) and whole blood was developed. Zeeman background correction and graphite tubes with L’vov platforms were used. Samples were ¶diluted with HNO₃/Triton X-100 and pipetted directly ¶into the graphite tube. Ashing, pretreatment and atomization steps were optimized carefully for the different fractions and elements applying different matrix modifiers ¶for each element. For the lymphocyte fraction a multi-fold injection technique was applied. Low detection limits ¶of the ETAAS method (Cd 0.13 μg/L, Cr 0.11 μg/L, ¶Cu 0.52 μg/L, Mn 0.13 μg/L, Se 0.7 μg/L of whole blood) combined with small quantities of sample necessary for analysis allow determination of trace elements in this matrix. Verification of possible differences in the trace element status of humans was performed with statistical significance (P < 0.05). In addition, a contribution to the determination of normal values of essential elements was achieved. The method was applied for determination of trace elements in human blood and blood fractions of two groups (n = 50) different in health status.     

Determination of aluminum levels in serum and red blood cells from long-term haemodialysis patients using instrumental neutron activation analysis

Aluminum levels of serum and red blood cell (RBC) were determined by instrumental neutron activation analysis (INAA) in 15 patients undergoing long-term haemodialysis. In the sample, aluminum was bombarded with thermal neutrons due to ²⁷Al(n,γ)²⁸Al and was determined by measuring 1779 keV gamma-ray of ²⁸Al (T _1/2 = 2.24 min) with a HPGe detector. Phosphorus, causing an important interference by the fast neutron reaction, ³¹P(n,α)²⁸Al, was determined by the photometric method to correct the net-area under the ²⁸Al gamma-peak. The one-sample Kolmogorov-Smirnov test was used to control the normality distribution of the aluminum levels in serum and RBC. The results obtained were found to be in agreement with the serum aluminum determination performed by electrothermal atomic absorption spectrophotometry. The statistical results show a correlation between the aluminum levels of serum and RBC. This revised version was published online in July 2006 with corrections to the Cover Date.     

ETAAS method for the determination of Cd, Cr, Cu, Mn and Se in blood fractions and whole blood

An electrothermal atomic absorption method (ETAAS) for the direct determination of trace elements (Cd, Cr, Cu, Mn, Se) both in blood fractions (erythrocytes, plasma and lymphocytes) and whole blood was developed. Zeeman background correction and graphite tubes with L'vov platforms were used. Samples were diluted with HNO3/Triton X-100 and pipetted directly into the graphite tube. Ashing, pretreatment and atomization steps were optimized carefully for the different fractions and elements applying different matrix modifiers for each element. For the lymphocyte fraction a multi-fold injection technique was applied. Low detection limits of the ETAAS method (Cd 0.13 microgram/L, Cr 0.11 microgram/L, Cu 0.52 microgram/L, Mn 0.13 microgram/L, Se 0.7 microgram/L of whole blood) combined with small quantities of sample necessary for analysis allow determination of trace elements in this matrix. Verification of possible differences in the trace element status of humans was performed with statistical significance (P < 0.05). In addition, a contribution to the determination of normal values of essential elements was achieved. The method was applied for determination of trace elements in human blood and blood fractions of two groups (n = 50) different in health status.     

Quantification of key red blood cell folates from subjects with defined MTHFR 677C>T genotypes using stable isotope dilution liquid chromatography/mass spectrometry

Red blood cell (RBC) folate levels are established at the time of erythropoiesis and therefore provide a surrogate biomarker for the average folate status of an individual over the preceding four months. Folates are present as folylpolyglutamates, highly polar molecules that cannot be secreted from the RBCs, and must be converted into their monoglutamate forms prior to analysis. This was accomplished using an individual's plasma pteroylpolyglutamate hydrolase by lysing the RBCs in whole blood at pH 5 in the presence of ascorbic acid. Quantitative conversion of formylated tetrahydrofolate derivatives into the stable 5,10-methenyltetrahydrofolate (5,10-MTHF) form was conducted at pH 1.5 in the presence of [(13)C(5)]-5-formyltetrahydrofolate. The resulting [(13)C(5)]-5,10-MTHF was then used as an internal standard for the formylated forms of tetrahydrofolate that had been converted into 5,10-MTHF as well any 5,10-MTHF that had been present in the original sample. A stable isotope dilution liquid chromatography-multiple reaction monitoring/mass spectrometry method was validated and then used for the accurate and precise quantification of RBC folic acid, 5-methyltetrahydrofolate (5-MTHF), tetrahydrofolate (THF), and 5,10-MTHF. The method was sensitive and robust and was used to assess the relationship between different methylenetetrahydrofolate reductase (MTHFR) 677C>T genotypes and RBC folate phenotypes. Four distinct RBC folate phenotypes could be identified. These were classified according to the relative amounts of individual RBC folates as type I (5-MTHF >95%; THF <5%; 5,10-MTHF <5%), type II (5-MTHF <95%; THF 5% to 20%; 5,10-MTHF <5%), type III (5-MTHF >55%; THF >20%; 5,10-MTHF >5%), and type IV (5-MTHF <55%; THF >20%; 5,10-MTHF >5%).     

Determination of selenium in bread-wheat samples grown under a Se-supplementation regime in actual field conditions

Selenium is an essential micronutrient for humans and animals, yet it is deficient in at least one billion people worldwide. Plants and plant-derived products transfer the soil-uptaken selenium to humans; therefore, the cultivation of plants enriched in selenium can be an effective way to improve the selenium status on humankind. This paper focuses on determining the ability of bread wheat to accumulate selenium after supplementation. One of the methods for supplementing this element in plants is foliar application with selenium solutions. These supplemented crop of wheat samples—bread wheat; Triticum aestivum L.—were used to determine if there is an increase of selenium content in cereal grains by comparing them with cereals cultivated in 2009 and harvested in 2010 with no supplementation. The experiments were done using sodium selenate and sodium selenite at three different selenium concentrations: 4, 20 and 100 g per hectare. Total Se is assessed by cyclic neutron activation analysis (CNAA), through short irradiations on the fast pneumatic system (SIPRA) of the Portuguese Research Reactor (RPI-ITN). The short-lived nuclide ^77mSe, that features a half-lifetime of 17.5 s, was used to determine the Se content in SIPRA. The experiment was successful, since the selenium concentration increased in the cropped grains and reached values up to 35 times the non-supplemented ones.     

Biliary excretion of essential trace elements in rats under oxidative stress caused by selenium deficiency

The excretion of essential trace elements, namely, Se, Sr, As, Mn, Co, V, Fe, and Zn into the bile of Se-deficient (SeD) Wistar male rats was studied using the multitracer (MT) technique, and instrumental neutron activation analysis (INAA). Normal and Se-control (SeC) rat groups were used as reference groups to compare the effects of Se levels on the behaviors of the essential trace elements. The excretion (% dose) of Se, Sr, As, Mn, Co, and V increased with Se levels in the liver. The biliary excretion of Mn and As dramatically enhanced for SeC rats compared with SeD rats, while that of V accelerated a little for SeC rats. The radioactivity levels of ⁵⁹Fe and ⁶⁵Zn in the MT tracer solution were insufficient to measure their excretion into bile. The role of glutathione and bilirubin for biliary excretion of the metals was discussed in relation to Se levels in rat liver.     

The determination of selenium in urine

The selenium excreted in urine can be measured to assess the dietary status of selenium, an essential trace element in human nutrition. The objectives of this work were: 1) to develop a procedure, capable of high sample throughout, by which the major interferences can be reduced such that selenium concentrations can be measured in urine by Neutron Activation Analysis (NAA) using^77mSe (17.4 s; and 2) to apply the method to a human dietary selenium study in which several selenium monitors were compared. The method involves a pre-irradiation arsenic-coprecipitation separation of the selenium from urine in the presence of a high specific-activity⁷⁵Se tracer. The processed urine samples are analyzed using NAA. The procedure was applied to 58 urine specimens longitudinally collected from 12 subjects consuming three different levels of selenium. A dose-response relationship was observed in urine as well as a high correlations with both serum and whole blood selenium concentrations.     

Nanometer‐sized alumina packed microcolumn solid‐phase extraction combined with field‐amplified sample stacking‐capillary electrophoresis for the speciation analysis of inorganic selenium in environmental water samples

In this paper, a new method of nanometer‐sized alumina packed microcolumn SPE combined with field‐amplified sample stacking (FASS)–CE‐UV detection was developed for the speciation analysis of inorganic selenium in environmental water samples. Self‐synthesized nanometer‐sized alumina was packed in a microcolumn as the SPE adsorbent to retain Se(IV) and Se(VI) simultaneously at pH 6 and the retained inorganic selenium was eluted by concentrated ammonia. The eluent was used for FASS–CE–UV analysis after NH₃ evaporation. The factors affecting the preconcentration of both Se(IV) and Se(VI) by SPE and FASS were studied and the optimal CE separation conditions for Se(IV) and Se(VI) were obtained. Under the optimal conditions, the LODs of 57 ng L^?1 (Se(IV)) and 71 ng L^?1 (Se(VI)) were obtained, respectively. The developed method was validated by the analysis of a certified reference material of GBW(E)080395 environmental water and the determined value was in a good agreement with the certified value. It was also successfully applied to the speciation analysis of inorganic selenium in environmental water samples, including Yangtze River water, spring water, and tap water.     

Simultaneous quantification of 17 trace elements in blood by dynamic reaction cell inductively coupled plasma mass spectrometry (DRC-ICP-MS) equipped with a high-efficiency sample introduction system

A quadrupole inductively coupled plasma mass spectrometer (Q-ICP-MS) equipped with a dynamic reaction cell (DRC) and coupled with a desolvating nebulization system (APEX-IR) was employed to determine 17 elements (Al, As, Ba, Cd, Co, Cr, Li, Mn, Mo, Ni, Pb, Sb, Se, Sn, Sr, V, and Zr) in blood samples. Ammonia (for Al, Cr, Mn, and V) and O₂ (for As and Se) were used as reacting gases. Selection of the best flow rate of the gases and optimization of the quadrupole dynamic bandpass tuning parameter (RPq) were carried out, using digested blood diluted 1 + 9 with deionized water and spiked with 1 μg L⁻¹ of Al, Cr, Mn, V and 5 μg L⁻¹ of As and Se. Detection limits were determined in digested blood using the 3σ criterion. The desolvating system allowed a sufficient sensitivity to be achieved to determine elements at levels of ng L⁻¹ without detriment of signal stability. The accuracy of the method was tested with the whole blood certified reference material (CRM), certified for Al, As, Cd, Co, Cr, Mn, Mo, Ni, Pb, Sb, Se, and V, and with indicative values for Ba, Li, Sn, Sr, and Zr. The addition calibration approach was chosen for analysis. In order to confirm the DRC data, samples were also analyzed by means of sector field inductively coupled plasma mass spectrometry (SF-ICP-MS), operating in medium (m/Δm = 4000) and high (m/Δm = 10,000) resolution mode and achieving a good agreement between the two techniques.     

Preliminary Study on the Changes of IgA/VcA Titers in Low Blood Selenium Persons1 Sera by Oral use of Selenium-Enriched Yeast

Abstract

Whole blood selenium (Se) concentrations in 112 IgA/VcA positive and 33 oral administrating Se—enriched yeast subjects and 32 IgA/VcA negative ones were determined, using 2,3—diaminonaphahalene fluorometric method modified by the author. The blood Se levels ([xbar] ± SD) of IgA/VcA positive and negative subjects were 0.115 ± 0.024, 0.118 ± 0.028 μg/ml. respectively, no significant difference was existed between their blood Se levels (P > 0.20). The blood Se levels of low blood Se subjects with IgA/VcA positivity were 0.104 ± 0.009, 0.149 ± 0.033 μg/ml, respectively, before and after oral use of Se—enriched yeast, there were significant differences between their blood Se levels (P < 0.001). However, the efficiency of Se—enriched yeast on the negative change of IgA/VcA titer was only 21.4%. It suggested that blood Se levels are not related with IgA/VcA titers.     

Determination and speciation of selenium in water samples collected from Muğla (Turkey) province by hydride generation atomic absorption spectrometry

In this work, determination of selenium in various water samples was done by using hydride generation atomic absorption spectrometry. The most appropriate values of HCl concentration, NaBH₄ concentration, NaOH concentration, flow rate of argon and flow rate of waste solution were determined. The optimum concentration of the HCl, NaBH₄ and NaOH solutions were found to be 7.0 mol L^?1, 1.0% and 0.75%, respectively. The optimum flow rate of Ar gas and waste solution were also found to be 100.9 mL min^?1 and 4.0 mL min^?1, respectively. Values of LOD and LOQ were calculated separately for total Se and Se(IV). LOD and LOQ values were calculated 0.56 μg L^?1, 1.87 μg L^?1 for total Se and 0.72 μg L^?1, 2.40 μg L^?1 for Se(IV), respectively. The precision was evaluated by relative standard deviation (RSD%) was found to be 3.5% for total Se and 3.1% for Se(IV) (n = 11). A standard reference material (NIST 1643e) was used in order to check the accuracy of the proposed method. There was a good agreement between certified and found values for standard reference material. The method was applied to the analysis of total Se and Se(IV) concentrations in tap water samples collected from the various regions of Mu?la. Proposed method showed spike recovery ranges from 92% to 116% in water samples.     

Analysis of the toenail as a biomonitor of supranutritional intake of Zn,Cu, and Mg

The toenail was examined as a biological monitor of Mg, Zn, and Cu intake using an observational case control model. The One Source Cohort matched 63 individuals in Columbia Missouri who took the One Source multivitamin with 63 control individuals. The matching criteria were based on age, sex, ethnicity, smoking status, and body mass index. The multivitamin contained supra-nutritional levels of Se, Mg, Cu, and Zn. The toenail clippings were examined for these elements using instrumental neutron activation analysis (INAA). A statistical analysis did not indicate a significant difference for Mg, Cu, or Zn between the nails of One Source supplement users and control subjects (p<0.76, 0.55, and 0.85, respectively). The trace nutrient Se was used as an internal control. Previous studies have consistently demonstrated that toenail Se is positively correlated with Se supplement use and the analysis did result in a significant correlation in the toenails of One Source users and control subjects (p<1·10⁻⁴). This internal Se control suggests that the One Source Cohort is largely free from misclassification errors that could interfere with the biomonitor response for the supranutritional intake of Mg, Cu, and Zn.     

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 selenium^{7 5}Se 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.     

Simultaneous speciation analysis of glutathione peroxidase,selenoprotein P and selenoalbumin in human serum by tandem anion exchange-affinity HPLC and on-line isotope dilution ICP-quadrupole MS

A method based on anion exchange (AE) and affinity (AF)-HPLC (AE-AF-HPLC) hyphenated to inductively coupled plasma-(quadrupole) mass spectrometry (ICP-QMS) was developed for the speciation analysis of selenoprotein P (SelP), glutathione peroxidase (GPx) and selenoalbumin (SeAlb) in human serum. AE-HPLC is proposed here for the on-line alleviation of Cl and Br spectral interferences on ⁷⁷Se (⁴⁰Ar³⁷Cl) and ⁸²Se (⁸¹Br¹H). Separation of GPx, SelP and SeAlb by AE-AF-HPLC was obtained within a total chromatographic runtime of <20 min. On-line (post-column) isotope dilution (ON-ID) and on-line external calibration (ON-EC)-ICP-QMS were used for the quantification of Se in GPx, SelP and SeAlb. ON-EC using a Se-L-cystine standard was shown to be a suitable approach for the routine simultaneous speciation analysis of serum GPx, SelP and SeAlb. The method validation was carried out by direct ICP-sector field MS determination of Se in GPx, SelP and SeAlb fractions collected after AE-AF-HPLC separation. In addition, the method accuracy for the determination of total protein-bound Se was assessed by analyzing a human serum reference material (BCR-637) certified for total Se content. Figure A methodology for the alleviation of Cl and Br interferences in the accurate simultaneous speciation analysis of glutathione peroxidase, selenoprotein P and selenoalbumin in human serum by affinity HPLC coupled on-line with ICP-quadrupole MS is proposed. This approach may be particularly useful for clinical laboratories that only have an ICP-quadrupole MS without a collision cell, or that lack an expensive ICP-SFMS (high-resolution) instrument     

Studies on the incorporation of Se in the presence of glutathione and the distribution of Zn,Co, Fe,Rb and Cs in mice by instrumental neutron activation analysis

The contents of Se, Fe, Co, Zn and Rb in several organs of Swiss mice were determined by instrumental neutron activation analysis (INAA) after injections with seleno-methionine (Se-Met) and glutathione (GSH). Se was accumulated in all examined organs and significant effects of the treatment with GSH on the distribution of Se were observed. An increase of Zn (or Se) content in blood after injection with Se-Met (or Zn²⁺ ions) was observed.     

Stability of selenium and its speciation analysis in water using automatic system separation and HR-ICP-MS measurement

A simple and convenient method has been developed for the pre-concentration and separation of inorganic selenium species from environmental water samples using anion exchange chromatographic column combined with high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) measurement. ⁷⁵Se(IV) and ⁷⁵Se(VI) were prepared and used as tracers during the experiments. The volatility of selenium during solution evaporation was investigated to establish a reliable water samples pretreatment procedure. The parameters which affect the uptake of Se(IV) and Se(VI) on Dowex1 × 8 resin was optimized and the procedure for Se(IV) and Se(VI) separation was proposed. Both Se(IV) and Se(VI) are retained on the column in natural or alkaline solution with high distribution coefficient. The successive gradient elution of pre-concentrated species of selenium with HNO₃ solution allows to differentiate between them. Se(IV) and Se(VI) finally were eluted with 0.05 mol/L HNO₃ and 5.0 mol/L HNO₃, respectively. The proposed method has been successfully verified using the certified reference materials (CRMs) of real water samples, and spiked recoveries for real samples were 98%-104% with 5% relative standard deviations (RSDs). The developed procedure is proved to be reliable and can be used for the rapid determination of selenium species in environmental water samples.     

Use of enriched <Superscript>74</Superscript>Se and <Superscript>77</Superscript>Se in combination with isotope pattern deconvolution to differentiate and determine endogenous and supplemented selenium in lactating rats

A quantitative methodology has been developed to differentiate between endogenous and supplemented selenium in lactating rats using two enriched selenium isotopes. Lactating rats were fed for 2 weeks with formula milk containing one enriched Se isotope, ⁷⁷Se, as the metabolic tracer. The isotopic composition of selenium in serum and urine samples was then measured by collision cell ICP-MS after the addition of a solution containing another enriched isotope, ⁷⁴Se, as quantitation tracer, before analysis. Isotope pattern deconvolution allowed the transformation of measured Se isotopic abundances into concentrations of natural abundance (endogenous) selenium and enriched ⁷⁷Se (supplemented) present in the samples. The proposed methodology was validated using serum and urine reference materials spiked with both ⁷⁷Se and ⁷⁴Se. The obtained results are discussed in terms of selenium exchange and half-life in lactating rats (11–12 days) and selenium levels in serum in comparison with non-supplemented rats and control rats after maternal feeding.     

Instrumental neutron activation analysis of blood serum

Instrumental neutron activation analysis has been used to determine 15 trace elements in twelve blood serum samples taken from healthy students at Bilkent University in Ankara. The method allowed the determination of Sc, Cr, Mn, Fe, Co, Zn, Se, Rb, Cs, Ce, Eu, Tb, Hf, Ta and Hg, which occur at the g.ml^–1 to ng.ml^–1 levels. There are no values reported for Tb, Hf, Ce, Eu and Ta before. The other results are compared with the values reported in the literature. Most are in the range of the reported values except for Fe, Zn, Se and Cs.     

Surfactant/oil/water system for the determination of selenium in eggs by graphite furnace atomic absorption spectrometry

An oil-in-water formulation has been optimized to determine trace levels of selenium in whole hen eggs by graphite furnace atomic absorption spectrometry. This method is simpler and requires fewer reagents when compared with other sample pre-treatment procedures. Graphite furnace atomic absorption spectrometric (GF AAS) measurement was carried out using standard addition calibration and Pd as a modifier. The precision, expressed as relative standard deviation, was better than 5% and the limit of detection was 1 µg L^− 1. The validation of the method was performed against a standard reference material Whole Egg Powder (RM 8415), and the measured Se corresponded to 95.2% of the certified value. The method was used for the determination of the Se level in eggs from hens treated with Se dietary supplements. Inorganic and organic Se sources were added to hen feed. The Se content of eggs was higher when hens were fed with organic Se compared to the other treatments. The proposed method, including sample emulsification for subsequent Se determination by GF AAS has proved to be sensitive, reproducible, simple and economical.     

Slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry for the determination of As and Se in soil and sludge

Slurry sampling electrothermal vaporization (ETV) inductively coupled plasma mass spectrometry (ICP-MS) has been applied to determine As and Se in soil and sludge samples. The influences of instrument operating conditions and slurry preparation on the ion signals were reported. Pd and ascorbic acid were used as mixed modifiers to enhance the ion signals. The effectiveness of ETV sample introduction technique for alleviating various spectral interferences in ICP-MS analysis has been demonstrated. This method has been applied to determine As and Se in NIST SRM 2709 San Joaquin soil reference material and NIST SRM 2781 domestic sludge reference material and a farmland soil sample collected locally. Since the sensitivities of As and Se in slurry solution and aqueous solution were different, analyte addition technique was used to determine As and Se in these samples. The As and Se analysis results of the reference materials agreed with the certified values. The precision between sample replicates was better than 5% for all determinations. The method detection limit estimated from analyte addition curves was about 0.03 and 0.02 μg g⁻¹ for As and Se, respectively, in original soil and sludge samples.