共查询到20条相似文献,搜索用时 15 毫秒
1.
Determination of isotopic composition of lithium by neutron activation analysis; comparison with mass spectrometry 总被引:1,自引:0,他引:1
An activation analysis method is described for routine determination of6Li-abundances in various lithium compounds on the basis of the reaction sequence6Li(n,α)T and16O(t, n)18F and the measurement of18F. Irradiations of diluted equeous solutions of samples containing CrO3 as internal flux monitor were carried out at a thermal neutron flux density of ϕ≤1011 n·cm−2·sec−1. Interferences from variations in neutron self-shielding oxygen concentration and triton range do not exceed 0.5% when using
the dilution technique. The results for6Li abundances from 3.52 to 7.60% with standard deviations of 1 to 2.5% were confirmed by mass spectrometric measurements. 相似文献
2.
Nuzhat Jabeen Ejaz ur Rehman Shafaat Ahmed 《Journal of Radioanalytical and Nuclear Chemistry》2003,258(2):427-430
The isotopic composition of lithium in seawater has been determined by thermal ionization mass spectrometry (TIMS) based on the use of lithium hydroxide as the ion source. Isotopic measurements in a reference material supplied by IAEA (L-SVEC Li2CO3) were made to check the reproducibility of the method and 6Li indicates mobilization of light isotope of lithium form the sediment. 相似文献
3.
K. Heydorn P. Z. Skanborg R. Gwozdz J. O. Schmidt M. E. Wacks 《Journal of Radioanalytical and Nuclear Chemistry》1977,37(1):155-168
The fast transfer system in the DR 2 reactor for irradiation at a thermal neutron flux density of 1013 n·cm−2·sec−1 was used for the determination of lithium by the7Li(n, γ)8Li reaction. β-counting with a large perspex Cerenkov detector begun at 0.3 s after the end of irradiation, and multi-scaler
data was accumulated in 300 channels at 0.1 s per channel. With a suitable choice of discrimination level only16N and background interfere, and the 0.84 s half-life of8Li was resolved by the method of weighted least squares. Results are presented for 36 international geochemical reference
materials, and for a few biological samples, including BOWEN's kale and the NBS Standard Reference Material 1571 Orchard Leaves. 相似文献
4.
Trace impurities of lithium in graphite is one of the sources of tritium in high-temperature reactors. To determine contents of less then 1ng/g a procedure based on the (n,)-reaction of6Li was developed. The samples are irradiated in a reactor and then ignited in a Wickbold apparatus. Thereby the tritium produced by the (n,)-reaction is completely converted in HTO, which can be easily purified by distillation and, if necessary, by a scavenger precipitation step. Several types of graphite have been investigated and the lowest content measured was 0.2 ng/g. 相似文献
5.
Plutonium isotopic composition and the activities of non-separate transuranic elements:237Np and241Am, are determined in the presence of long lived-fission products traces, by gamma-spectrometric measurements with a Ge-ultrapure
detector. The quantitative values from the gamma-spectra analysis, are presented comparatively to mass-spectrometric data.
This work has been done under AIEA, UNPD 7455/Rom. program. 相似文献
6.
S. E. Glover R. H. Filby S. B. Clark 《Journal of Radioanalytical and Nuclear Chemistry》1998,234(1-2):201-208
The determination of isotopic thorium by alpha-spectrometric methods is a routine practice for bioassay and environmental
measurement programs. Alpha-spectrometry has excellent detection limits (by mass) for all isotopes of thorium except232Th due to its extremely long half-life. This paper reports a pre-concentration neutron activation analysis (PCNAA) method
for232Th that may be performed following alpha-spectrometry if a suitable source preparation material is utilized. Human tissues
and other samples were spiked with229Th and the thorium was isolated from the sample using ion exchange chromatography. The thorium was then electrodeposited from
a sulfate-based medium onto a vanadium planchet, counted by alpha-spectrometry, and then analyzed for232Th by neutron activation analysis. The radiochemical yield was determined from the alpha-spectrometric method. Detection limits
for232Th by this PCNAA method are approximately 50 times lower than achieved by alphaspectrometry. 相似文献
7.
Determination of isotopic composition of boron 总被引:4,自引:0,他引:4
K. L. Ramakumar A. R. Parab P. S. Khodade A. I. Almaula S. A. Chitambar H. C. Jain 《Journal of Radioanalytical and Nuclear Chemistry》1985,94(1):53-61
Investigations were carried out on the determination of isotopic composition of boron using Cs2BO
2
+
ion and thermal ionisation mass spectrometry. The results show distinct advantage over the normally used Na2BO
2
+
ion. 相似文献
8.
R. Pretorius P. P. Coetze M. Peisach 《Journal of Radioanalytical and Nuclear Chemistry》1973,16(2):551-558
The coincident measurement of both nuclear products at their complementary angles was used to determine6Li by the reactions6Li(d, α)4He and6Li(p, α)3He, and7Li by the reaction7Li(p, α)4He. Elemental lithium was determined in natural samples or samples of known isotopic composition. Isotopic analyses could
be carried out over the entire range from 0 to 100 atom% with a relative standard deviation of about 4%. The CMCP technique
is highly specific and effectively eliminates interference and background. 相似文献
9.
Z. B. Alfassi J. P. F. Sellschop 《Journal of Radioanalytical and Nuclear Chemistry》1989,135(5):341-348
Simultaneous determination of boron and lithium is done by double irradiation with protons. One irradiation with 1.55 MeV protons and another with 7.4 MeV protons, measuring in both cases the amount of7Be formed /7Li/p,n/7Be and10B/p,/7Be/. Deuteron bombardment was not found to be of much advantage. 相似文献
10.
Chifang Chai Yongzhong Liu Xueying Mao 《Journal of Radioanalytical and Nuclear Chemistry》1996,204(1):159-165
The isotopic abundance ratios of190Os/184Os and96Ru/102Ru for the metal phases of the Jilin and Taonan stone meteorites were determined by pretreatment and radiochemical neutron activation analysis. All experimental factors affecting Os and Ru isotopic ratios were discussed, including sampling, standard, irradiation, separation and counting. The statistical errors of measurement for the199Os/184Os ratio can be controlled within 1%. The experimental results indicate that the statistically significant anomalies of the190Os/184Os and96Ru/102Ru ratios have not been found relative to the terrestrial Os and Ru standards. 相似文献
11.
W. Maenhaut 《Analytica chimica acta》1975,75(1):31-39
A method has been developed for the simultaneous determination of 17 trace elements in gallium arsenide. The method involves reactor neutron irradiation of the samples, distillation of the arsenic matrix activity and Ge(Li) γ-ray spectrometry. For a sample size of 0.1 g and a 10-day irradiation at 2·1013 n cm-2 s-1, the detection limits vary from 70 p.p.b. (tin) down to 5·10-3 p.p.b. (scandium). 相似文献
12.
A method for the elemental analysis of copper and bronze objects is described. Na, Co, Ni, Cu, Zn, As, Ag, Sn, Sb, W, Ir and Au are determined through instrumental neutron activation analysis. Mg, Al, V, Ti and Mn are determined after chemical separation using anionic exhange. The detection limits for a number of other elements are also given. Results for NBS standard reference materials are presented and the results compared with the recommended values. The agreement is good. The results of the analysis of five ancient bronze and two copper objects are presented. 相似文献
13.
J. Y. Yang C. L. Tseng J. M. Lo M. H. Yang 《Fresenius' Journal of Analytical Chemistry》1985,321(2):141-145
Summary Lithium in environmental, biological and metal samples was determined by neutron activation analysis via the6Li(n,)T and16O(T,n)18F reactions. The samples were converted to aqueous solutions either by dissolution or by digestion and their aliquots were irradiated in a nuclear reactor for 2 h. The irradiated sample solution, was placed in a ZrO2 column on which the18F nuclide was adsorbed. Most of the coexisting nuclides24Na,82Br,38Cl,64Cu, etc. were separated by elution with pH 1 3 solution. The column was subjected to a Ge(Li) detector for-ray spectrometry. The lithium content in the sample was estimated from the18F activity obtained. The matrix effect can be eliminated by either strong dilution of the samples in aqueous medium or by the method of standard addition. Lithium can be determined with high precision and accuracy in sub-ppm samples.
Bestimmung von Lithiumspuren in biologischen, Umwelt- und Metallproben mit Hilfe der Neutronenaktivierungsanalyse
Zusammenfassung Lithium wird über die Reaktionen6Li(n,)T und16O(T,n)18F bestimmt. Die Proben werden durch Auflösung oder Aufschluß in wäßrige Lösung übergeführt und im Reaktor 2 h lang bestrahlt. Die bestrahlte Lösung wird auf eine ZrO2-Säule gegeben, wo die18F-Nuklide adsorbiert werden. Die meisten anderen Nuklide (24Na,82Br,38Cl,64Cu usw.) werden durch Elution mit Säurelösung pH 1 3 abgetrennt. Die-Spektrometrie erfolgt mit einem Ge(Li)-Detektor. Der Lithiumgehalt ergibt sich aus der18F-Aktivität. Durch starke Verdünnung oder durch das Standardzugabeverfahren kann der Matrixeffekt eliminiert werden. Lithium ist so mit hoher Präzision und Genauigkeit in sub-ppm-Proben bestimmbar.相似文献
14.
Y. Yamada K. Yasuike M. Itoh N. Kiriyama K. Komura K. Ueno 《Journal of Radioanalytical and Nuclear Chemistry》1995,201(5):381-390
A neutron activation method based on the measurement of tritium radioactivity produced by6Li (n,)3H reaction was applied to determine the isotopic abundance of6Li in aqueous solution with known lithium concentration. Tritium radioactivity was measured with a low background liquid scintillation counter over a period of 2000 min. The present method demonstrated a good linearity between the isotopic abundance of6Li and tritium radioactivity produced per unit amount of lithium in a wide range of lithium concentration. A comparison of the present data with those from mass spectrometry showed agreement, though our method was 10 times less sensitive, than mass spectrometry. The present new approach should thus prove quite useful for determining the isotopic abundance of6Li. 相似文献
15.
This paper reports the measurement of the Neodymium isotopic composition by Neptune Multiple Collector Inductively Coupled
Plasma Mass Spectrometry (MC-ICP-MS) over the last two years. Although there is concomitant Cerium in the chemical separation
process, this has no significant influence on the Neodymium analysis. As for the sample containing small amounts of Samarium
(Sm/Nd < 0.04), direct calibration for isobaric interference and mass discrimination by the exponential law can be obtained
by assuming that Samarium mass discrimination is the same as that of Neodymium. Geological samples after traditional chemical
separation were measured by Neptune MC-ICP-MS and Thermal Ionization Mass Spectrometry (TIMS) respectively. The results show
that Neptune MC-ICP-MS can measure Neodymium isotopic composition as precisely the TIMS does and is even more effective and
less time-consuming than the TIMS Method.
__________
Translated from Chinese Journal of Analytical Chemistry, 2007, 35(1): 71–74 [译自: 分析化学] 相似文献
16.
The conventional absorbance-ratio technique for determining the isotopic composition of lithium by atomic absorption spectrometry is improved by the use of “ultimate absorbance ratios” of sample solutions. These ratios are obtained by extrapolating the linear portion of lithium content/absorbance-ratio plots to the intercept at 0 mol m?3 lithium. These graphs are obtained measuring the absorbances of solutions of known 6Li abundance and of various lithium contents with natural and 6Li-enriched lithium hollow-cathode lamps. Linear calibration is attained over the range 0.0–99.3% 6Li, and the lithium isotopic abundance can be determined with an absolute error of ±0.7% 6Li for > 0.01 mol m?3 lithium solutions. The method requires neither prior measurement of the total lithium content in sample solutions nor adjustment of the content to match that in the standard solutions. 相似文献
17.
R. Verma J. Arunachalam S. Gangadharan J. C. Vyas G. P. Kothiyal M. K. Gupta 《Fresenius' Journal of Analytical Chemistry》1992,344(6):261-264
Summary Coprecipitation behaviour of As, Au, Co, Cr, Cu, Eu, Fe, Ir, La, Lu, Mn, Mo, Nb, Ni, Pd, Pt, Sb, Sc, Ta, W, Zn and Zr during precipitation of hydrous oxide of niobium from lithium niobate was investigated. The matrix was dissolved in HF-HNO3, evaporated to dryness and niobium was precipitated from HNO3-H2O2 medium. The recovery studies were made using radiotracers. A radiochemical separation scheme based on group precipitation has been developed for the determination of Au, Co, Cr, Cu, Fe, Mn, Ni, Pd, Pt, Zn, Zr and rare earth elements. The method was applied to the analysis of lithium niobate. This analysis has provided fruitful information for improving the quality of the crystal. 相似文献
18.
Determination of activable isotopic tracers of zinc by neutron activation analysis for study of bioavailability of zinc 总被引:1,自引:0,他引:1
Bang-Fa Ni Pingsheng Wang Yingjun Luo Shouyang Yu 《Journal of Radioanalytical and Nuclear Chemistry》1991,151(2):255-260
A procedure of pre-irradiation concentration of zinc in fecal samples using anion exchanger was developed for the study of the bioavailability of zinc by neutron activation analysis. The mass ratios between70Zn and68Zn, or64Zn and their contents between natural zinc and enriched zinc are used to calculate the bioavailability of zinc when the abundance of the isotope70Zn is not high ehough. 相似文献
19.
G. Wauters C. Vandecasteele K. Strijckmans 《Journal of Radioanalytical and Nuclear Chemistry》1989,134(1):221-232
This paper considers the variable isotopic composition of lead as a possible source of systematic errors in proton activation analysis. The importance of this source of error was evaluated for environmental and geological samples. As proton activation analysis is frequently used for the certification of lead, the error was determined for three sediment reference materials. Inductively coupled plasma-mass spectrometry was used for the determination of the isotopic composition of lead. The systematic error amounted for the sediments to approximately 1%. 相似文献
20.
The determination of lithium and nitrogen in a variety of materials by thermal neutron activation is described. The nuclear reactions used are 14N(n,p)14C and 6 Li(n,α)3H. Radionuclides. 14C and 3H for counting are isolated by fusion of the irradiated sample in a vacuum system. Data are presented on lithium and nitrogen concentrations in several terrestrial standards. The new method allows reliable measurements on 10–50-mg samples. 相似文献