共查询到20条相似文献,搜索用时 31 毫秒
1.
S. Eisenhut K. G. Heumann A. Vengosh 《Fresenius' Journal of Analytical Chemistry》1996,354(7-8):903-909
A technique for precise boron isotope ratio measurements with a high detection power has been developed by negative thermal ionization mass spectrometry (NTIMS). Relative standard deviations in the range of 0.03–0.3% have been obtained for the determination of the 11B/10B isotope ratio using nanogram amounts of boron. Ba(OH)2 has been applied as ionization promoter for the formation of negative thermal ions. By adding MgCl2 better reproducibilities of the measurement have been achieved. A possible interference of BO-2 ions at mass number 42 by CNO- could be excluded by the sample preparation technique used. Contrary to other NTI techniques no dependence of the measured isotope ratio on the boron amount used has been observed. Anthropogenic and natural saline influences in ground water have been successfully identified by boron isotope ratio determinations with this NTIMS method, due to the different isotopic composition of boron in natural and anthropogenic substances. In sewage, the boron isotope ratio is substantially influenced by washing powder, which contains low 11B/10B ratios (expressed in 11B values normalized to the standard reference material NIST SRM 951). In contaminated ground water, low 11B values are normally correlated with high boron and high chloride concentrations. On the other hand, 11B shifts to higher values in less contaminated samples. For ground water with saline influences, only the 11B determination, and not the boron or chloride content, allowed the correct identification of this natural source of contamination. 相似文献
2.
Tea I Kosieradzka K Antheaume I Gentil E Robins RJ 《Analytical and bioanalytical chemistry》2011,401(4):1263-1271
The quality of the determination of compound-specific isotopic content at natural abundance by gas chromatography–isotope
ratio measurement–mass spectrometry (GC-irm-MS) relies on the stability of the voltage generated by the ion detector Faraday
cages. The application of GC-irm-MS to the determination of δ13C (‰) and δ15N (‰) is now routine. However, for numerous applications, it is necessary to determine both the isotope content (δ15N) and the quantity (in micromoles) of analyte present. We now show that it is possible for nitrogen-containing compounds
to measure how much analyte is present with an irm mass spectrometer linked to a GC by exploiting the integrated N2 total ion current intensity (Vs) generated by measuring the 15N/14N isotope ratio. The method is validated over a range of concentration (2–70 mmol/L) and δ15N (−70 to +50‰) values for six molecules of diverse chemical nature and functionality (nortropine, norpseudotropine, nortropinone,
cysteine, taurine, glutathione). It is shown that once the ion current is calibrated, the quantitative values are of a comparable
quality to those obtained from GC with flame ionization detection (GC-FID). In addition, it is demonstrated that over a definable
range, the δ15N (‰) value is independent of the quantity of analyte introduced, confirming the validity of this method. 相似文献
3.
《Spectrochimica Acta Part B: Atomic Spectroscopy》2006,61(3):314-318
A new method for the determination of isotopic ratio of boron using Zeeman effect background correction-graphite furnace atomic absorption spectrometry with conventional atomizer and natural-boron hollow cathode source is described. The isotope-shift Zeeman effect at 208.9 nm is utilized for isotopic ratio determination. At a given concentration of total boron, the net absorbance decreases linearly with increasing 10B/11B ratio. The absorbances are recorded at the field strength of 1.0 T. The isotope ratios measured by the proposed method were in good agreement with the results obtained by inductively coupled plasma-quadruple mass spectrometry or thermal ionization mass spectrometry. The present method is fairly fast and less expensive compared to the above techniques and is quite suitable for plant environments. 相似文献
4.
Katarzyna Kosieradzka Illa Tea Emmanuel Gentil Richard J. Robins 《Analytical and bioanalytical chemistry》2010,396(4):1405-1414
An important route for the detoxification of tropane alkaloids involves N-demethylation to the nor-compounds followed by further degradation. In order to study the mechanisms of the pertinent reactions,
a suitable means to determine the isotope ratios of the substrates and products is required. However, the polarity and functionality
of the nortropane compounds makes their analysis as free bases difficult. A method is described which allows both the quantification
of nortropane alkaloids and the determination of their natural abundance δ15N values. The protocol exploits the derivatisation of the alkaloids by reaction with ethyl chloroformate in aqueous medium
and the quantitative extraction of the ensuing ethylcarbamate esters. The improved chromatographic properties of these derivatives
gives ample separation of the isomeric nortropine and norpseudotropine for measurement of their δ15N (‰) values by isotope ratio mass spectrometry interfaced to gas chromatography. Adequate separation could not be achieved
with the underivatised compounds. Repeatability and precision are sufficient to allow differences in the δ15N values (∆δ15N) > 0.8‰ to be measured, with a standard deviation routinely ∼0.3‰. The methodology has been tested by determining the changes
in the δ15N values of nortropine and norpseudotropine during degradation by cell suspension cultures of a Pseudomonas strain expressing a specific capacity for tropine catabolism. The precision and reproducibility are shown sufficient to allow
the evolution of the δ15N values to be followed during the fermentation. 相似文献
5.
A technique for precise boron isotope ratio measurements with a high detection power has been developed by negative thermal ionization mass spectrometry (NTIMS). Relative standard deviations in the range of 0.03-0.3% have been obtained for the determination of the (11)B/(10)B isotope ratio using nanogram amounts of boron. Ba(OH)(2) has been applied as ionization promoter for the formation of negative thermal ions. By adding MgCl(2) better reproducibilities of the measurement have been achieved. A possible interference of BO(-)(2) ions at mass number 42 by CNO(-) could be excluded by the sample preparation technique used. Contrary to other NTI techniques no dependence of the measured isotope ratio on the boron amount used has been observed. Anthropogenic and natural saline influences in ground water have been successfully identified by boron isotope ratio determinations with this NTIMS method, due to the different isotopic composition of boron in natural and anthropogenic substances. In sewage, the boron isotope ratio is substantially influenced by washing powder, which contains low (11)B/(10)B ratios (expressed in delta(11)B values normalized to the standard reference material NIST SRM 951). In contaminated ground water, low delta(11)B values are normally correlated with high boron and high chloride concentrations. On the other hand, delta(11)B shifts to higher values in less contaminated samples. For ground water with saline influences, only the delta(11)B determination, and not the boron or chloride content, allowed the correct identification of this natural source of contamination. 相似文献
6.
Methyl-branched fatty acids (MBFAs) are the dominant form of fatty acid found in many bacteria. They are also found at low
levels in a range of foodstuffs, where their presence has been linked to bacterial sources. In this study we evaluated the
potential of compound-specific isotope analysis to obtain insights into the stable carbon isotope ratios (δ13C values in ‰) of individual MBFAs and to compare them to the stable carbon isotope ratios of straight-chain fatty acids in
food. Due to their low abundance in foodstuffs, the MBFAs were enriched prior to gas chromatography coupled to isotope ratio
mass spectrometric (GC–IRMS) analysis. After transesterification, urea complexation was used to suppress the 16:0 and 18:0
methyl esters that were dominant in the samples. Following that, silver-ion high performance liquid chromatography was used
to separate the saturated from the unsaturated fatty acids. The resulting solutions of saturated fatty acids obtained from
suet, goat’s milk, butter, and human milk were studied by GC–IRMS. The δ13C values of fatty acids with 12–17 carbons ranged from −25.4‰ to −37.6‰. In all samples, MBFAs were most depleted in carbon-13,
followed by the odd-chain fatty acids 15:0 and 17:0. 14:0 and 16:0 contained the highest proportions of carbon-13. The results
from this study illustrate that MBFAs have distinctive δ13C values and must originate from other sources and/or from very different substrates. These measurements support the initial
hypothesis that δ13C values can be used to attribute MBFAs to particular sources. 相似文献
7.
An on-line Hg reduction technique using stannous chloride as the reductant was applied for accurate and precise mercury isotope ratio determinations by multi-collector (MC)-ICP/MS. Special attention has been paid to ensure optimal conditions (such as acquisition time and mercury concentration) allowing precision measurements good enough to be able to significantly detect the anticipated small differences in Hg isotope ratios in nature. Typically, internal precision was better than 0.002% (1 RSE) on all Hg ratios investigated as long as approximately 20 ng of Hg was measured with a 10-min acquisition time. Introducing higher amounts of mercury (50 ng Hg) improved the internal precision to <0.001%. Instrumental mass bias was corrected using 205Tl/203Tl correction coupled to a standard-sample bracketing approach. The large number of data acquired allowed us to validate the consistency of our measurements over a one-year period. On average, the short-term uncertainty determined by repeated runs of NIST SRM 1641d Hg standard during a single day was <0.006% (1 RSD) for all isotope pairs investigated (202Hg/198Hg, 202Hg/199Hg, 202Hg/200Hg, and 202Hg/201Hg). The precision fell to <0.01% if the long-term reproducibility, taken over 11 months (over 100 measurements), was considered. The extent of fractionation has been investigated in a series of sediments subject to various Hg sources from different locations worldwide. The ratio 202Hg/198Hg expressed as δ values (per mil deviations relative to NIST SRM 1641d Hg standard solution) displayed differences from +0.74 to −4.00‰. The magnitude of the Hg fractionation per amu was constant within one type of sample and did not exceed 1.00‰. Considering all results (the reproducibility of Hg standard solutions, reference sediment samples, and the examination of natural samples), the analytical error of our δ values for the overall method was within ±0.28‰ (1 SD), which was an order of magnitude lower than the extent of fractionation (4.74‰) observed in sediments. This study confirmed that analytical techniques have reached a level of long-term precision and accuracy that is sufficiently sensitive to detect even small differences in Hg isotope ratios that occur within one type of samples (e.g., between different sediments) and so far have unequivocally shown that Hg isotope ratios in sediments vary within approximately 5‰. 相似文献
8.
MeHg and inorganic Hg compounds were measured in aqueous media for isotope ratio analysis using aqueous phase derivatization,
followed by purge-and-trap preconcentration. Compound-specific isotope ratio measurements were performed by gas chromatography
interfaced to MC-ICP/MS. Several methods of calculating isotope ratios were evaluated for their precision and accuracy and
compared with conventional continuous flow cold vapor measurements. An apparent fractionation of Hg isotopes was observed
during the GC elution process for all isotope pairs, which necessitated integration of signals prior to the isotope ratio
calculation. A newly developed average peak ratio method yielded the most accurate isotope ratio in relation to values obtained
by a continuous flow technique and the best reproducibility. Compound-specific isotope ratios obtained after GC separation
were statistically not different from ratios measured by continuous flow cold vapor measurements. Typical external uncertainties
were 0.16‰ RSD (n = 8) for the 202Hg/198Hg ratio of MeHg and 0.18‰ RSD for the same ratio in inorganic Hg using the optimized operating conditions. Using a newly
developed reference standard addition method, the isotopic composition of inorganic Hg and MeHg synthesized from this inorganic
Hg was measured in the same run, obtaining a value of δ
202Hg = −1.49 ± 0.47 (2SD; n = 10). For optimum performance a minimum mass of 2 ng per Hg species should be introduced onto the column. 相似文献
9.
Mg isotope fractionation in biogenic carbonates of deep-sea coral, benthic foraminifera, and hermatypic coral 总被引:1,自引:0,他引:1
Yoshimura T Tanimizu M Inoue M Suzuki A Iwasaki N Kawahata H 《Analytical and bioanalytical chemistry》2011,401(9):2755-2769
High-precision Mg isotope measurements by multiple collector inductively coupled plasma mass spectrometry were applied for
determinations of magnesium isotopic fractionation of biogenic calcium carbonates from seawater with a rapid Mg purification
technique. The mean δ26Mg values of scleractinian corals, giant clam, benthic foraminifera, and calcite deep-sea corals were −0.87‰, −2.57‰, −2.34‰,
and −2.43‰, suggesting preferential precipitation of light Mg isotopes to produce carbonate skeleton in biomineralization.
Mg isotope fractionation in deep-sea coral, which has high Mg calcite skeleton, showed a clear temperature (T) dependence from 2.5 °C to 19.5 °C: 1,000 × ln(α) = −2.63 (±0.076) + 0.0138 (±0.0051) × T(R
2 = 0.82, p < 0.01). The δ26Mg values of large benthic foraminifera, which are also composed of a high-Mg calcite skeleton, can be plotted on the same
regression line as that for deep-sea coral. Since the precipitation rates of deep-sea coral and benthic foraminifera are several
orders of magnitude different, the results suggest that kinetic isotope fractionation may not be a major controlling factor
for high-Mg calcite. The Mg isotope fractionation factors and the slope of temperature dependence from deep-sea corals and
benthic foraminifera are similar to that for an inorganically precipitated calcite speleothem. Taking into account element
partitioning and the calcification rate of biogenic CaCO3, the similarity among inorganic minerals, deep-sea corals, and benthic foraminiferas may indicate a strong mineralogical
control on Mg isotope fractionation for high-Mg calcite. On the other hand, δ26Mg in hermatypic corals composed of aragonite has been comparable with previous data on biogenic aragonite of coral, sclerosponges,
and scaphopad, regardless of species differences of samples. 相似文献
10.
Characterization of ganoderma spore lipid by stable carbon isotope analysis: implications for authentication 总被引:2,自引:0,他引:2
Liu X Xu SP Wang JH Yuan JP Guo LX Li X Huang XN 《Analytical and bioanalytical chemistry》2007,388(3):723-731
The ratios of stable carbon isotopes (13C/12C) of ganoderma fruiting body, ganoderma spore, ganoderma spore lipid (GSL) and individual fatty acids in GSL were determined
by gas chromatography–stable isotope ratio mass spectrometry and elemental analysis–stable isotope ratio mass spectrometry.
These values fall into a range from −26.9 to −23.3‰, suggesting that the cut log as the Ganoderma-cultivated substrate in Fujian, China, may belong to C3 plants. Eighteen fatty acids were identified and their abundances
measured by gas chromatography–mass spectrometry in the six GSL samples with C16:0, C18:0, C18:1 and C18:2 as major constituents, and C16:1 is evidently enriched compared with the other edible vegetable oils. On the basis of the compositions of fatty acids and
stable carbon isotopes in GSL, we have developed a novel method to detect the adulteration of GSL products with cheaper edible
vegetable oils. An example of ideal blending between GSL and C4 or C3 vegetable oil is further provided to expound the discrimination
procedures and corresponding sensitive indicators. Simultaneously, the carbon isotope fractionation in the biosynthesis of
individual fatty acids was observed, revealing that the formation of C18:0 from C16:0 in ganodema spores had no conspicuous 13C enrichment of +0.4‰ for Ganoderma sinensis spore and +0.1‰ for G. lucidum spore; the desaturation of C18:0 to C18:1 resulted in a distinct 13C depletion of −1.4‰ for G. sinensis spore and −0.9‰ for G. lucidum spore; and the next desaturation from C18:1 to C18:2 displayed no evident 13C fractionation of −0.1‰ for G. sinensis spore and −0.2‰ for G. lucidum spore.
Figure
Ganoderma lucidum has been widely used in traditional Chinese medicines. Ganoderma spore lipid (GSL) extracted from the spores of G. lucidum has been approved as a health food supplement. However, because of rarity, GSL has become a target for adulteration with
cheaper vegetable oils. 相似文献
11.
Alexis Gilbert Virginie Silvestre Richard J. Robins Gérald S. Remaud 《Analytical and bioanalytical chemistry》2010,398(5):1979-1984
The application of isotope ratio methods in authenticity and traceability relies on the accuracy and robustness of the methodology
employed. An unexpected source of error has now been identified, which can introduce major and variable inaccuracies into
the determination of site-specific isotope ratio measurement by quantitative 13C NMR spectrometry if not correctly controlled. This is the isotope chemical shift effect, which comes into play when hydrogen
atoms in the target molecule enter into exchange with deuterated water present at trace levels in the deuterated solvent used
as the frequency lock. Even at a level of contamination as low as 0.02%, an error of 5‰ can be introduced, fivefold the required
accuracy of 1‰. How to avoid this source of error is discussed. 相似文献
12.
Mas JL Ma R McLeod C González-Labajo J Cox A Watson P 《Analytical and bioanalytical chemistry》2006,386(1):152-160
The 234U/238U isotope ratio has been widely used as a tracer for geochemical processes in underground aquifers. Quadrupole-based inductively
coupled plasma mass spectrometry (ICP-MS) equipped with a high-efficiency nebulizer and a membrane desolvator was employed
for the determination of 234U/238U isotope ratios in natural water samples. The instrumental limit of detection for 234U was at the low pg L−1 level with very low sample consumption. Measurement precision (234U/238U) was 3–5% for bottled mineral water with elevated uranium concentration (>1 μg L−1). For the analysis of groundwater samples from the Almonte-Marisma underground aquifer (Huelva, Spain), uranium was stripped
from stainless steel planchets that had previously been used as radiometric counting sources for alpha-particle spectrometry.
Potential spectral interferences from other metals introduced during the dissolution were investigated. Matrix-matched blank
solutions were needed to subtract the background on 234U due to the formation of platinum argides, and to allow for mass bias correction and background correction. The Pt appears
to be an impurity present in the stainless steel, either as a minor component by itself or after extraction from the anode
and a subsequent uranium electrodeposition. The 234U/238U isotope ratio data were in very good agreement with those of alpha spectrometry, while precision was improved by a factor
of up to 10 and counting time was reduced down to ~20 min (10 replicate measurements). 相似文献
13.
Knobbe N Vogl J Pritzkow W Panne U Fry H Lochotzke HM Preiss-Weigert A 《Analytical and bioanalytical chemistry》2006,386(1):104-108
The stable carbon and nitrogen isotopic composition of urine and milk samples from cattle under different feeding regimes
were analysed over a period of six months. The isotope ratios were measured with isotope ratio mass spectrometry (IRMS). The
δ
13C values of milk and urine were dependent on different feeding regimes based on C3 or C4 plants. The δ
13C values are more negative under grass feeding than under maize feeding. The δ
13C values of milk are more negative compared to urine and independent of the feeding regime. Under grass feeding the analysed
milk and urine samples are enriched in 13C relative to the feed, whereas under maize feeding the 13C/12C ratio of urine is in the same range and milk is depleted in 13C relative to the diet. The difference between the 15N/14N ratios for the two feeding regimes is less pronounced than the 13C/12C ratios. The δ
15N values in urine require more time to reach the new equilibrium, whereas the milk samples show no significant differences
between the two feeding regimes. 相似文献
14.
Summary Selenite and selenate were determined in ground waters with isotope dilution mass spectrometry (IDMS). This species analysis was possible by the use of an82Se enriched selenite and selenate spike and a Chromatographic separation of both species after the isotope dilution step. In a column filled with the DEAE cellulose anion exchanger selenite could be separated with 1 mol/l formic acid, whereas selenate was eluted with 0.1 mol/1 nitric acid. The mass spectrometric isotope ratio measurement was carried out in a thermal ionization instrument using the formation of negative Se– thermal ions for detection. Selenite, selenate and total selenium in ground water samples were determined in the concentration range of 0.2–20 n/g with relative standard deviations of 0.5%–5%. The selenate concentration was approximately ten to eighty times higher than the corresponding selenite concentration. There was always a difference of about 8% between the sum of the selenite and selenate concentrations and the total selenium concentration which can possibly be attributed to water-soluble selenides and elementary selenium, respectively.
Herrn Prof. Dr. R. Neeb zum 60. Geburtstag gewidmet 相似文献
Herrn Prof. Dr. R. Neeb zum 60. Geburtstag gewidmet 相似文献
15.
The analysis of boron in ore and glass samples was attempted by prompt proton spectrometry. A deuteron bombarding energy of
2.7 MeV was chosen to coincide with a region where the excitation function of the10B(d, p)11B reaction did not vary appreciably with the energy. The intensity of the ground-state protons, emerging at an angle of 30°,
was used as a measure of the boron content. Targets were prepared by a technique whereby approximately 300 μg/cm2 deposits of powdered samples were centrifuged from a methanol suspension onto tantalum discs. Concentrations down to 0.2%
were determined. Possible interference by other elements, particularly nitrogen, magnesium and titanium, was investigated
but found to be of little consequence mainly because of the highQ-value of the10B(d, p)11B reaction. 相似文献
16.
A. Lamberty V. Holland A. Verbruggen F. Hendrickx P. De Bièvre 《Fresenius' Journal of Analytical Chemistry》1988,332(6):645-647
Summary A method for the isotope dilution mass spectrometric (IDMS) determination of boron in rye grass at the 5 g · g–1 level has been developed. The mass spectrometric measurements are performed using negative thermal ionization at masses 42 (10B16O16O–) and 43 (11B16O16O–). The 10B/11B ratios are corrected for the 10B16O17O– contribution at mass 43 and for mass fractionation. The chemical blank is determined using the standard addition method. The numerical calculations are done with a least square fit computer program. The method has been applied for the certification of boron in BCR 281 (Rye Grass). The boron content of this reference material has been established as (5.64±0.56) g·g–1.
Bestimmung von Borspuren in Rye Grass BCR 281 durch Isotopenverdünnungs-Massenspektrometrie相似文献
17.
Pitois A de las Heras LA Zampolli A Menichetti L Carlos R Lazzerini G Cionini L Salvatori PA Betti M 《Analytical and bioanalytical chemistry》2006,384(3):751-760
Boron neutron capture therapy (BNCT) is a bimodal radiotherapeutic treatment based on the irradiation of neoplastic tissues
with neutrons after the tissues have selectively accumulated molecules loaded with nuclides with large neutron capture cross-sections
(such boron-10). Boron-10 carriers have been tested to a limited extent, and clinical trials have been conducted on sulfhydryl
borane (10B-BSH) and boronophenylalanine (10B-BPA). However, precise and accurate measurements of boron-10 concentrations (0.1–100 μg/g) in specimens and samples of limited
size (μg scale) are needed in order to be able to biologically characterise new compounds in predictive tissue dosimetry,
toxicology and pharmacology studies as well as in clinical investigations. A new approach based on fast separation and detection
of 10B-BPA performed by coupling capillary electrophoresis to electrospray mass spectrometry is reported. This method allows the
quantitative analysis and characterisation of 10B-BPA in a short time with a high separation efficiency. Detection limits of 3 μM for 10B-BPA and 30 ng/mL for 10B were obtained with CE–ESI–MS. A quantification limit of 10 μM for 10B-BPA (100 ng/mL for 10B) was attained. The total boron-10 concentration was determined by high-resolution inductively coupled mass spectrometry
in order to validate the method. Boron-10 isotope measurements were carried out by HR–ICP–MS at medium resolution (R=4000)
due to the presence of an isobaric interference at mass 10. Good agreement was obtained between the values from CE–ESI–MS
and those from HR–ICP–MS. The method has been successfully used to determine the 10B-BPA in two lines of cultured cells. 相似文献
18.
Helmar Wiltsche Karl Prattes Michael Zischka Günter Knapp 《Spectrochimica Acta Part B: Atomic Spectroscopy》2009
In the production of 10B enriched steels, the production–recycling process needs to be closely monitored for inadvertent mix-up of materials with different B isotope levels. A quick and simple method for the estimation of boron isotope ratios in high alloyed steels using high resolution continuum source flame AAS (HR-CS-FAAS) was developed. On the 208.9 nm B line the wavelength of the peak absorption of 10B and 11B differs by 2.5 pm. The wavelength of the peak absorption of boron was determined by fitting a Gauss function through spectra simultaneously recorded by HR-CS-FAAS. It was shown that a linear correlation between the wavelength of the peak absorption and the isotope ratio exists and that this correlation is independent of the total boron concentration. Internal spectroscopic standards were used to compensate for monochromator drift and monochromator resolution changes. Accuracy and precision of the analyzed samples were thereby increased by a factor of up to 1.3. Three steel reference materials and one boric acid CRM, each certified for the boron isotope ratio were used to validate the procedure. 相似文献
19.
To avoid mass interferences on analyte ions caused by argon ions and argon molecular ions via reactions with collision gases,
an rf hexapole filled with helium and hydrogen has been used in inductively coupled plasma mass spectrometry (ICP–MS), and
its performance has been studied. Up to tenfold improvement in sensitivity was observed for heavy elements (m > 100 u), because
of better ion transmission through the hexapole ion guide. A reduction of argon ions Ar+ and the molecular ions of argon ArX+ (X = O, Ar) by up to three orders of magnitude was achieved in a hexapole collision cell of an ICP–MS (“Platform ICP”, Micromass,
Manchester, UK) as a result of gas-phase reactions with hydrogen when the hexapole bias (HB) was set to 0 V; at an HB of 1.6
V argon, and argon-based ions of masses 40 u, 56 u, and 80 u, were reduced by approximately four, two, and five orders of
magnitude, respectively. The signal-to-noise ratio 80Se/ 40Ar2
+ was improved by more than five orders of magnitude under optimized experimental conditions. Dependence of mass discrimination
on collision-cell properties was studied in the mass range 10 u (boron) to 238 u (uranium). Isotopic analysis of the elements
affected by mass-spectrometric interference, Ca, Fe, and Se, was performed using a Meinhard nebulizer and an ultrasonic nebulizer
(USN). The measured isotope ratios were comparable with tabulated values from IUPAC. Precision of 0.26%, 0.19%, and 0.12%,
respectively, and accuracy of 0.13% 0.25%, and 0.92%, respectively, was achieved for isotope ratios 44Ca/ 40Ca and 56Fe/57Fe in 10 μg L–1 solution nebulized by means of a USN and for 78Se/80Se in 100 μg L–1 solution nebulized by means of a Meinhard nebulizer.
Received: 15 December 2000 / Revised: 26 March 2001 / Accepted: 27 March 2001 相似文献
20.
D. Gabunia O. Tsagareishvili L. Gabunia G. Darsavelidze 《Journal of solid state chemistry》2006,179(9):2944-2948
Real structure and some physicomechanical characteristics of the samples of natural beta-rhombohedral boron B as well as of its 10B and 11B monoisotopes have been studied. It was shown that the influence of 10B and 11B isotopes on physicomechanical properties of boron had a different character. In particular, the samples enriched with 11B had high values of microhardness, shear modulus (SM) and elastic limit if compared to those of boron, while the samples enriched with 10B monoisotopes were characterized with high values of thermal expansion coefficient (TEC) and thermal conductivity; lattice parameters a and c increased by the sequence: 11B, B, 10B. It was established that TEC, thermal conductivity, microhardness, SM and shear elastic limit increased in all samples at annealing for 5 h at 1500 °C regardless of isotope content. 相似文献