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.     

Sequential photocatalyst-assisted digestion and vapor generation device coupled with anion exchange chromatography and inductively coupled plasma mass spectrometry for speciation analysis of selenium species in biological samples

We have developed an on-line sequential photocatalyst-assisted digestion and vaporization device (SPADVD), which operates through the nano-TiO₂-catalyzed photo-oxidation and reduction of selenium (Se) species, for coupling between anion exchange chromatography (LC) and inductively coupled plasma mass spectrometry (ICP-MS) systems to provide a simple and sensitive hyphenated method for the speciation analysis of Se species without the need for conventional chemical digestion and vaporization techniques. Because our proposed on-line SPADVD allows both organic and inorganic Se species in the column effluent to be converted on-line into volatile Se products, which are then measured directly through ICP-MS, the complexity of the procedure and the probability of contamination arising from the use of additional chemicals are both low. Under the optimized conditions for SPADVD – using 1 g of nano-TiO₂ per liter, at pH 3, and illuminating for 80 s – we found that Se(IV), Se(VI), and selenomethionine (SeMet) were all converted quantitatively into volatile Se products. In addition, because the digestion and vaporization efficiencies of all the tested selenicals were improved when using our proposed on-line LC/SPADVD/ICP-MS system, the detection limits for Se(IV), Se(VI), and SeMet were all in the nanogram-per-liter range (based on 3σ). A series of validation experiments – analysis of neat and spiked extracted samples – indicated that our proposed methods could be applied satisfactorily to the speciation analysis of organic and inorganic Se species in the extracts of Se-enriched supplements.     

Hyphenated techniques for speciation of Se in in vitro gastrointestinal digests of Saccharomyces cerevisiae

A method was developed allowing the separation, detection and identification of Se species extracted from yeast supplements during simulated digestion processes. The in vitro gastric and intestinal digests were studied for their Se compounds by successive high-performance liquid chromatography–inductively coupled plasma mass spectrometry (HPLC-ICP-MS) and high-performance liquid chromatography–electrospray tandem mass spectrometry (HPLC-ES-MS-MS) analyses. The conditions for the separation were chosen as to be compatible with both ICP-MS and ES-MS-MS detection. HPLC-ICP-MS was used to screen the extracts for their Se content. By means of HPLC-ES-MS-MS, the compounds extracted were identified on-line according to their retention time, m/z of the molecular ion and the presence of typical product ions. From these results, it was clear that the main compound extracted by both gastric and intestinal fluid was Se-methionine, which was also the main Se compound extracted by proteolytic digestion from the yeast supplements. Two other minor compounds could be identified as Se-cystine and Se(O)-methionine, a degradation product of Se-methionine.     

Determination of uranium, thorium and plutonium isotopes by ICP-MS

Quantitative and isotopic measurement of actinide elements is required in many circumstances in the nuclear industry. For example, determination of very low levels of these alpha emitters in human urine samples is used to assess the internal committed dose for nuclear workers. Quantifying actinide isotopes in radioactive waste from nuclear processing and nuclear facility decommissioning provides important information for waste management. Accurate determination of the uranium isotopic ratios in reactor fuels provides fuel burnup information. Inductively coupled plasma mass spectrometry (ICP-MS) has been used for the determination of Th, U, and Pu in various samples including urine, nuclear waste, and nuclear fuel in our laboratory. In order to maximize the capability of the technique and ensure quality analyses, ICP-MS was used to analyze samples directly, or after pre-treatment to separate complicated matrices or to concentrate the analyte(s). High-efficiency sample introduction techniques were investigated. Spectral interferences to minor isotopes caused by peak tails and hydride ions of major actinide isotopes were studied in detail using solutions prepared with light and heavy waters. The quality of the isotopic ratio measurement was monitored using standard reference materials.     

A rapid in vitro assay of cobalamin in human urine and medical tablets using ICP-MS

A rapid and simple as well as sensitive inductively coupled plasma mass spectrometry (ICP-MS) method for the determination of cobalamin is described. Cobalamin in human urine and medicine tablet solutions was converted on-line into free cobalt ions in acid medium, the cobalt ions were then detected by ICP-MS. Cobalamin was determined by measuring the increase of integral counts per second intensity, which was linear over the cobalamin concentration range of 1.0 × 10⁻¹⁰ g mL⁻¹ to 8.0 × 10⁻⁵ g mL⁻¹, and the limit of detection was 0.05 ng mL⁻¹ (3σ). At the pump rate of 30 rotations per minute, one analysis cycle of cobalamin, including sampling and washing, could be accomplished in 0.5 min with the relative standard deviations of less than 5 %. The proposed procedure was applied successfully in monitoring cobalamin in human urine without any pretreatment process and in rapid determination of cobalamin in multivitamin tablets.     

Liquid chromatography–mass spectrometry (LC–MS): a powerful combination for selenium speciation in garlic (Allium sativum)

Liquid chromatography (LC) hyphenated with both elemental and molecular mass spectrometry has been used for Se speciation in Se-enriched garlic. Different species were separated by ion-pair liquid chromatography–inductively coupled plasma mass spectrometry (LC–ICP–MS) after hot-water extraction. They were identified by on-line reversed-phase liquid chromatography–electrospray ionization tandem mass spectrometry (RPLC–ESI–MS–MS). Se-methionine and Se-methylselenocysteine were determined by monitoring their product ions. Another compound, γ-glutamyl-Se-methylselenocysteine, shown to be the most abundant form of Se in the garlic, was determined without any additional sample pre-treatment after extraction and without the need for a synthesized standard. Product ions for this dipeptide were detected by LC–ESI–MS–MS for three isotopes of Se—⁷⁸ Se, ⁸⁰Se: and ⁸²Se. The method was extended to the species extracted during in-vitro gastrointestinal digestion. Because both Se-methylselenocysteine and γ-glutamyl-Se-methylselenocysteine have anticarcinogenic properties, their extractability and stability during human digestion are very important. Garlic was also treated with saliva, to enable detection and analysis of species extracted during mastication. Detailed information on the extractability of selenium species by both simulated gastric and intestinal fluid are given, and variation of the distribution of Se among the different species with time is discussed. Although the main species in garlic is the dipeptide γ-glutamyl-Se-methylselenocysteine, Se-methylselenocysteine is the main compound present in the extracts after treatment with gastrointestinal fluids. Two more, so far unknown compounds were observed in the chromatogram. The extracted species and their transformations were analysed by combining LC–ICP–MS and LC–ESI–MS–MS. In both the simulated gastric and intestinal digests, Se-methionine, Se-methylselenocysteine, and γ-glutamyl-Se-methylselenocysteine could be determined by LC–ESI–MS–MS by measuring their typical product ions.      

Purification and characterization of two major selenium-containing proteins in selenium-rich silkworm pupas

Selenium (Se) is an essential trace element in vivo involved in the defense against oxidative stress. Se deficiency is associated with many human diseases. The bioactivity of Se is dose- and species-dependent. Silkworm pupa has been reported to accumulate Se mainly in proteins. Thus the characterization of major Se-containing proteins is very important in the application of Se-rich silkworm pupas in food and drugs. In this study, crude proteins were extracted from Se-rich silkworm pupas, followed by DEAE-Sepharose and Sephedex G-75 chromatography. Se content was measured after each step to determine the highest Se-containing fraction for the next step of separation. The proteins obtained were analyzed using SDS-PAGE, followed by in-gel digestion with trypsin, and were characterized by MALDI-TOF MS and ESI-MS/MS. These data showed two proteins mainly accumulated Se in the silkworm pupas. Those two proteins were proven by mass spectrometry to be arylphorin and sex-specific storage-protein 2 precursor (SP-2), respectively. Both of them belong to the storage proteins of amino acids during metamorphosis and the non-feeding pupal stage. The results suggest that Se could be enriched by storage proteins and be supplied to silkworm pupas in accompany with amino acids for the synthesis of new Se-containing proteins and peptides.     

Flow injection on-line dilution for multi-element determination in human urine with detection by inductively coupled plasma mass spectrometry

A simple flow injection on-line dilution procedure with detection by inductively coupled plasma mass spectrometry (ICP-MS) was developed for the determination of copper, zinc, arsenic, lead, selenium, nickel and molybdenum in human urine. Matrix effects were minimized by employing a dilution factor of 16.5 with on-line standard addition, and (103)Rh was used as internal standard to compensate for signal fluctuation. The procedure was validated by the analysis of two standard reference materials SRM 2670 (NIST) and Seronormtrade mark Trace Elements in Urine. Recovery experiments were performed by spiking the reference materials as well as artificial urine. The detection limits (mug l(-1)) were 0.12,0.96,0.30,0.09,0.45,0.08,0.09, and the precisions (RSD,%) were 2.6,2.3,3.0,3.7,3.7,4.9,2.8 for Cu, Zn, As, Pb, Se, Ni and Mo, respectively. The procedure was applied to the analysis of 41 human urine samples. No correlations between the concentrations of the elements were observed.     

补充富硒小麦和富硒玉米对大鼠血硒状态影响的对比观察

给克山病病区粮喂养６周的大鼠补充富硒小麦或富硒玉米,观察了大鼠血硒和血ＣＳＨ－Ｐｘ活性的变化。结果显示,补充富硒小麦和富硒玉米均可有效地升高大鼠血浆硒、红细胞硒和红细胞ＧＳＰ－Ｐｘ活性,且两种形式硒的作用效果相同;停止补硒后,补充富硒小麦组大鼠的红细胞和红细胞ＧＳＨ－Ｐｘ活性均显著高于补充富硒玉米组大鼠。表明给大鼠补充富硒小麦较补充富硒玉米好。     

Determination of Cd,Hg, Pb and Se in sediments slurries by isotopic dilution calibration ICP-MS after chemical vapor generation using an on-line system or retention in an electrothermal vaporizer treated with iridium

A method for the determination of Cd, Hg, Pb and Se in sediments reference materials by slurry sampling chemical vapor generation (CVG) using isotopic dilution (ID) calibration and detection by inductively coupled plasma mass spectrometry (ICP-MS) is proposed. Two different systems were used for the investigation: an on-line flow injection system (FI-CVG-ICP-MS) and an off-line system with in situ trapping electrothermal vaporization (CVG-ETV-ICP-MS). About 100 mg of the reference material, ground to a particle size ≤50 μm, was mixed with acid solutions (aqua regia, HF and HCl) in an ultrasonic bath. The enriched isotopes ¹¹¹Cd, ¹⁹⁸Hg, ²⁰⁶Pb and ⁷⁷Se were then added to the slurry in an adequate amount in order to produce an altered isotopic ratio close to 1. For the on-line system, a standing time for the slurry of 12 h before measurement was required, while for the batch system, no standing time is needed to obtain accurate results. The conditions for the formation of the analyte vapor were optimized for the evaluated systems. The following altered isotope ratios were measured: ¹¹¹Cd/¹¹⁴Cd, ¹⁹⁸Hg/¹⁹⁹Hg, ²⁰⁶Pb/²⁰⁸Pb e ⁷⁷Se/⁸²Se. The obtained detection limits in the on-line system, in μg g⁻¹, were: Cd: 0.15; Hg: 0.09; Pb: 6.0 and Se: 0.03. Similar detection limits were obtained with the system that uses the ETV: 0.21 for Hg, 6.0 for Pb and 0.06 μg g⁻¹ for Se. No signal for Cd was obtained in this system. One estuarine, two marine and two river certified sediments were analyzed to check the accuracy. The obtained values by both systems were generally in agreement with the certified concentrations, according to the t-test for a confidence level of 95%, demonstrating that isotope equilibration was attained in the slurries submitted to a chemical vapor generation procedure and detection by ICP-MS. The relative standard deviations were lower than 10%, adequate for slurry analysis. The almost quantitative analytes extractions to the aqueous phase of the slurry must favor equilibration of the added enriched isotope with the isotope in the sample, allowing the use of isotopic dilution calibration for slurry analysis.     

Urinary selenium speciation by high-performance liquid chromatography-inductively coupled plasma mass spectrometry: advantages of detection with a double-focusing mass analyser with a hydride generation interface

A detailed comparison of the performance of inductively coupled plasma mass spectrometry (ICP-MS), with quadrupole and double-focusing instruments for the speciation of selenium in urine has been carried out. Selenium sensitivity about 23-59 times higher with double-focusing ICP-MS detection was observed, but limits of detection were only 1-8.7 times better because of background noise. Selenium species separation has been carried out by both reversed-phase and vesicle-mediated high-performance liquid chromatography (HPLC), coupled on-line with the detector via conventional nebulization and via on-line focused microwave digestion-hydride generation. A remarkable improvement in sensitivity (28-110 times better for (77)Se depending on the chromatographic system) and elimination of interference problems from the urinary matrix or the components of the mobile phases were achieved when an on-line microwave digestion-hydride generation interface was used, but the background noise was much higher than with conventional nebulization. Therefore, the limits of detection were not as low as expected from such improvement in the sensitivity. More selenocompounds can be separated, and a slight improvement in the sensitivity and limits of detection was obtained when the vesicle-mediated HPLC system was used as compared with reverse-phase chromatography. However, the use of several complementary chromatographic systems, such as reverse-phase HPLC, is recommended to bring some light on the selenocompounds present in basal human urine. Comparative data of rat urine speciation are also given.     

Rapid determination of actinides in urine by inductively coupled plasma mass spectrometry and alpha spectrometry: A hybrid approach

A new rapid separation method that allows separation and preconcentration of actinides in urine samples was developed for the measurement of longer lived actinides by inductively coupled plasma mass spectrometry (ICP-MS) and short-lived actinides by alpha spectrometry; a hybrid approach. This method uses stacked extraction chromatography cartridges and vacuum box technology to facilitate rapid separations. Preconcentration, if required, is performed using a streamlined calcium phosphate precipitation. Similar technology has been applied to separate actinides prior to measurement by alpha spectrometry, but this new method has been developed with elution reagents now compatible with ICP-MS as well. Purified solutions are split between ICP-MS and alpha spectrometry so that long- and short-lived actinide isotopes can be measured successfully. The method allows for simultaneous extraction of 24 samples (including QC samples) in less than 3 h. Simultaneous sample preparation can offer significant time savings over sequential sample preparation. For example, sequential sample preparation of 24 samples taking just 15 min each requires 6 h to complete. The simplicity and speed of this new method makes it attractive for radiological emergency response. If preconcentration is applied, the method is applicable to larger sample aliquots for occupational exposures as well. The chemical recoveries are typically greater than 90%, in contrast to other reported methods using flow injection separation techniques for urine samples where plutonium yields were 70-80%. This method allows measurement of both long-lived and short-lived actinide isotopes. ²³⁹Pu, ²⁴²Pu, ²³⁷Np, ²⁴³Am, ²³⁴U, ²³⁵U and ²³⁸U were measured by ICP-MS, while ²³⁶Pu, ²³⁸Pu, ²³⁹Pu, ²⁴¹Am, ²⁴³Am and ²⁴⁴Cm were measured by alpha spectrometry. The method can also be adapted so that the separation of uranium isotopes for assay is not required, if uranium assay by direct dilution of the urine sample is preferred instead. Multiple vacuum box locations may be set-up to supply several ICP-MS units with purified sample fractions such that a high sample throughput may be achieved, while still allowing for rapid measurement of short-lived actinides by alpha spectrometry.     

Determination of selenium compounds in urine by high-performance liquid chromatography--inductively coupled plasma mass spectrometry

Selenium species, selenite, selenate, selenomethionine (Semet), seneloethionine (Seet) and trimethylselenonium ion (TmSe) were separated in aqueous solution using a gel-permeation (polyvinyl alcohol-based resin) GS-220 column by eluting with 25 mM tetramethylammonium hydroxide and 25 mM malonic acid at pH 7.9. The GS-220 column coupled with inductively coupled plasma mass spectrometry was used for the separation, identification, and quantification of selenium compounds present in certified reference material (CRM) No. 18 human urine from the National Institute for Environmental Studies in Japan (NIES). Spiking of the authentic standard to the urine and use of a silica-based LC-SCX cation-exchange column validated the peak of selenium compounds. High concentrations of chloride and bromide in the urine eluted from the GS-220 column formed molecular ions 40Ar37Cl+ and 81Br1H+ in the plasma, and these molecular ions created additional peaks in the chromatograms when 77Se and 82Se isotopes were monitored respectively. Thus, both the isotopes were selected concurrently for signal monitoring to eliminate the interfering signals. On the LC-SCX column, chloride and bromide were eluted with selenate and complicated its determination, but the peak of TmSe was baseline separated from rest of the Se compounds. Two unknown Se compounds were detected in both the columns. An additional Se compound having the same retention time as that of Semet was detected on the LC-SCX column. Peaks of selenite, selenate, TmSe and unknown selenium compounds in the urine were baseline separated on the GS-220 column, and were free from interferences. Therefore, the GS-220 column was used for the determination of selenium compounds in NIES CRM No. 18. Unknown Se compounds were the predominant selenium species followed by selenite, TmSe and selenate. The estimated value of TmSe as Se, by the standard additions method using the GS-220 column, was 3.42 +/- 0.17 microg l(-1) and was in good agreement with the LC-SCX value [3.38 +/- 0.21 (n=5) microg l(-1)].     

Identification of selenium species in urine by ion-pairing HPLC–ICP–MS using laboratory-synthesized standards

This study focused on the detection/identification of possible selenium metabolites in human urine. Organoselenium compounds not commercially unavailable were synthesized and characterized by electrospray mass spectrometry. Separation of selenomethionine, methylselenomethionine, trimethylselonium, selenoethionine, and selenoadenosylmethionine was achieved by ion-pairing HPLC with a mobile phase of 2 mmol L^–1 hexanesulfonic acid, 0.4% acetic acid, 0.2% triethanolamine (pH 2.5), and 5% methanol. The column effluent was introduced on-line to inductively coupled plasma–mass spectrometry for selenium-specific detection (⁷⁷Se and ⁷⁸Se). For selenium speciation in urine, solid-phase extraction was carried out using C₁₈ cartridges modified with hexanesulfonic acid. Selective retention of cationic species was observed from acidified urine (perchloric acid, pH 2.0). After elution with methanol, evaporation, and dissolution in the mobile phase, the sample was introduced to the HPLC–ICP–MS system and the chromatographic peaks were assigned by adding standards. The species identified in urine were selenomethionine, trimethylselonium ion, and selenoadenosylmethionine. The last species was detected for the first time and our results suggest that selenomethionine might enter the metabolic pathway of its sulfur analog in the activated methylation cycle.Kazimierz Wrobel and Katarzyna Wrobel are on the leave from the Institute of Scientific Research, University of Guanajuato, L. de Retana No. 5, 36000 Guanajuato, Gto., Mexico     

Speciation of metallothionein-like proteins of the mussel Mytilus edulis by orthogonal separation mechanisms with inductively coupled plasma-mass spectrometry detection: effect of selenium administration

Several complementary separation mechanisms (size-exclusion chromatography, SEC; fast protein liquid chromatography, FPLC; reverse-phase chromatography, RPC) have been coupled to inductively coupled plasma mass spectrometry (ICP-MS) detection to investigate the speciation of Cd, Se, Cu and Zn in mussel hepatopancreas. SEC with double-focusing (DF) ICP-MS detection was used first for speciation analysis of those four trace elements, both in uncontaminated mussels and in mussels exposed to Cd (500 μg l⁻¹) or to Cd+Se (500 μg l⁻¹ of each element). Observed SEC results indicated that Se does not seem to significantly bind to metallothionein-like proteins (MLPs) ‘in vivo’. Total cytosolic Cd and MLPs content were lower in Cd+Se exposed mussels than those exposed to Cd only. For each treatment, 50 μl of the SEC peak fraction containing the MLPs was used to perform fast protein liquid chromatography coupled ‘on-line’ with a quadrupole (Q) ICP-MS. ⁸²Se and ¹¹⁴Cd isotopes were simultaneously monitored. Four and five Cd/MLPs isoforms were then detected in mussels exposed to only Cd and Cd+Se, respectively. In contrast, no signs of Se/MLP isoforms were found for both treatments. Subsequently, the bulk of MLPs eluting from the FPLC system were isolated and lyophilizated. A 50-μl aliquot of such reconstituted lyophilisate was then injected into a Vydac C₈ Reverse-Phase column directly connected to the Q-ICP-MS. Results confirmed the presence of one more Cd/MLP peak in those mussels exposed to Cd+Se. However, the number of Cd/MLP peaks detected decreased to three and four in only Cd and Cd+Se exposed animals, respectively. These results tend to indicate that Se, which does not trigger the biosynthesis of MLPs, could probably orient such synthesis towards the generation of a new Cd/MLP isoform in mussels submitted to both elements. The possible interrelation/complementation between Se and MLP against Cd toxicity is discussed.     

Low level detection of <Superscript>135</Superscript>Cs and <Superscript>137</Superscript>Cs in environmental samples by ICP-MS

The measurement of fission product cesium isotopes ¹³⁵Cs and ¹³⁷Cs at low femtogram (fg) 10⁻¹⁵ levels in ground water by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) is reported. To eliminate the natural barium isobaric interference on the cesium isotopes, in-line chromatographic separation of the cesium from barium was performed followed by high sensitivity ICP-MS analysis. A high efficiency desolvating nebulizer system was employed to maximize ICP-MS sensitivity ~10 cps/fg. The three sigma detection limit for ¹³⁵Cs was 2 fg/mL (0.1 μBq/mL) and for ¹³⁷Cs 0.9 fg/mL (0.0027 Bq/mL) measured from the standard with analysis time of less than 30 min/sample. Cesium detection and 135/137 isotope ratio measurement at very low femtogram levels using this method in a spiked ground water matrix is also demonstrated.     

Structure of sputtered Co-Se thin films prepared for an application in catalysis

Co-Se thin films prepared by magnetron sputtering have shown significant activity for the oxygen reduction reaction. One sample, after sectioning by ultramicrotomy, was studied by high-resolution scanning transmission electron microscopy (HRSTEM) and scanning Auger microscopy (SAM), and X-ray diffraction (XRD) was used for characterizing further samples. These thin films were shown to have Co-Se nanocrystals embedded into Se-rich matrices. The TEM and XRD results were consistent with the nanocrystallites being non-stoichiometric with structures related to those of monoclinic Co_1−xSe (x=0.125-0.25).     

Determination of trimethylselenonium iodide, selenomethionine, selenious acid, and selenic acid using high-performance liquid chromatography with on-line detection by inductively coupled plasma mass spectrometry or flame atomic absorption spectrometry

An analytical method has been developed for the determination of selenious acid, selenic acid, trimethylselenonium ion, and selenomethionine. The four selenium compounds were separated by HPLC on a column (25 cm×4 mm I.D.) of the anion-exchanger ESA Anion III with a mobile phase (1.5 ml/min) of 0.0055 M ammonium citrate (pH 5.5). Detection was carried out using an on-line inductively coupled plasma mass spectrometer (ICP-MS) or a flame atomic absorption spectrometer (FAAS) as the selenium-specific detector. The chromatographic parameters and the chemical factors affecting the separation of the selenium species were optimized. The four selenium compounds could be separated within 8 minutes. The detection limits of the coupled HPLC–FAAS system were approximately 1 mg Se/l for each compound (100 μl injection), estimated as three times the base-line noise of the chromatograms. More powerful selenium detection was achieved with an ICP-MS. Selenium was measured at m/z 78. To increase the nebulization efficiency, the Meinhard concentric glass nebulizer was replaced by an ultrasonic nebulizer. The ICP-MS signal intensity was increased with the ultrasonic nebulization by a factor of 7 times for selenious acid and 24 to 31 times for trimethylselenonium ion, selenomethionine, and selenic acid compared to that with the Meinhard nebulization. The detection limits achieved by the HPLC–ICP-MS with the ultrasonic nebulization were 0.08 μg Se/l for trimethylselenonium ion, 0.34 μg Se/l for selenious acid, 0.18 μg Se/l for selenomethionine, and 0.07 μg Se/l for selenic acid, respectively.     

微波消解ICP-MS法测定广西北部湾海鸭蛋中硒和锗的含量

以硝酸-过氧化氢（体积比为5：3）混合溶液为消解剂,微波消解法处理海鸭蛋样品,采用电感耦合等离子体质谱法测定样品溶液中的硒和锗的含量。选择适合的同位素元素,运用碰撞室技术（CCT）降低多原子离子对元素硒、锗的干扰,用钇作为在线内标。硒、锗工作曲线的线性范围均为0．0-100．0ng／mL,相关系数r=0．9996;硒、锗的检出限分别为1．1,0．15ng／mL,测定结果的相对标准偏差分别为4．78％,5．70％（n=6）,加标回收率为92．2％-104．0％。用该法测定国家标准物质黄鱼（GBW08573）中硒的含量,测定值在标称值范围内。     

Determination of trace iron in indium phosphide wafer by on-line matrix separation and inductively coupled plasma mass spectrometry

A method for the determination of iron in indium phosphide (InP) wafer is proposed. In the present experiment, an on-line matrix separation system using an ion exchange column was combined with inductively coupled plasma mass spectrometry (ICP-MS) for the determination of ng g⁻¹ level of iron. In the on-line matrix separation, indium and iron in the sample solution was passed through a strongly-basic anion exchange resin column with the 9 M HCl carrier solution, where indium was eluted from the column and iron was adsorbed on it. Then, iron was eluted with the carrier solution of 0.3 M HCl containing 1 ng ml⁻¹ cobalt, and it was directly introduced into the ICP-MS nebulizer. In ICP-MS measurement, cobalt in the carrier solution was used as an internal standard to correct the change in sensitivity due to matrix effect, and the peak area integration was performed to quantify iron and cobalt in the integration time range of 20-60 s from the start of the cobalt solution flow. The detection limit (3σ) for iron was 3 ng g⁻¹, and the recoveries for iron in the 0.8, 2.4, and 8.0% indium solutions were almost 100%. The method was applied to the determination of iron in commercially available iron-doped InP wafers. The obtained results for InP wafer samples with the high iron concentration were in good agreement with those obtained by graphite furnace atomic absorption spectrometry (GFAAS).