Isotope analyses lithium

LITHIUM ISOTOPIC ANALYSIS From early Li isotope measurement to the modem era of analysis... 

Moriguti T, Nakamura E (1993) Precise lithium isotope analysis by thermal ionization mass spectrometry using lithium phosphate as an ion source. Proc Japan Acad Sci 69B 123-128 Moriguti T, Nakamura E (1998a) High-yield lithium separation and precise isotopic analysis for natural rock and aqueous samples. Chem Geol 145 91-104... 

Manning and Slavin (M3) also reported lithium isotope analysis by atomic absorption. The emission of an open, lithium-containing oxygen-... 

M3. Manning, D. C., and Slavin, W., Lithium isotope analysis by atomic absorption spectrophotometry. Atomic Absorption Newsletter No. 8. Perkin-Elmer Corp., Norwalk, Conn. (November 1962). 

S. Ahmed, N. Jabeen, and E. ur Rehman, Determination of Lithium Isotopic Composition by Thermal Ionization Mass Spectrometry, Anal. Chem. 2002, 74, 4133 L. W. Green, J. J. Leppinen, and N. L. Elliot, Isotopic Analysis of Lithium as Thermal Dilithium Fluoride Ions, Anal. Chem. 1988,60, 34. 

Lithium has two stable isotopes, Li and Li, which have abundances of 7.5% and 92.5%, respectively. Lithium is a soluble alkali element. Because its ionic radius is small (0.78 A), it behaves more like magnesium (0.72 A) than the alkalis. Li tends to substitute for Al, Fe, and especially for Mg " ". Because of their large relative mass difference, lithium isotopes have the potential to exhibit sizable fractionation, as has been demonstrated by high-precision isotopic analysis. 

The alkali elution curves of the displacement chromatography are shown in Fig. 17, the ratio Li/ Li dependent on the effluent volume is given in Fig. 18. As one can see from Fig. 18, an increase of the Li/ Li ratio from 0.07 to 0.09 is found within the lithium elution band which corresponds to a column length of 91 cm. The relative enrichment of the heavy lithium isotope Li in the first fractions — that is in the methanolic phase — agrees with isotopic separations of calcium using a condensation resin with dibenzo(18]crown-6 and [2b.2.2], respectively (Chap. 4.3.2.3 and Chap. 4.3.2.4). Fujine and coworkers have also carried out one breakthrough experiment with methanolic solutions of cesium chloride and lithium acetate The evaluation of the front analysis with Spedding and coworkers method resulted in an isotopic separation factor of a = 1.014. 

Lithium metabolism and transport cannot be studied directly, because the lack of useful radioisotopes has limited the metabolic information available. Lithium has five isotopes, three of which have extremely short half lives (0.8,0.2, 10 s). Lithium occurs naturally as a mixture of the two stable isotopes Li (95.58%) and Li (7.42%), which may be determined using Atomic Absorption Spectroscopy, Nuclear Magnetic Resonance Spectroscopy, or Neutron Activation analysis. Under normal circumstances it is impossible to identify isotopes by using AAS, because the spectral resolution of the spectrometer is inadequate. We have previously reported the use of ISAAS in the determination of lithium pharmacokinetics. Briefly, the shift in the spectrum from Li to Li is 0.015 nm which is identical to the separation of the two lines of the spectrum. Thus, the spectrum of natural lithium is a triplet. By measuring the light absorbed from hollow cathode lamps of each lithium isotope, a series of calibration curves is constructed, and the proportion of each isotope in the sample is determined by solution of the appropriate exponential equation. By using a dual-channel atomic absorption spectrometer, the two isotopes may be determined simultaneously. - ... 

PIGE is a rapid, non-destructive technique that is employed in the analysis of light elements such as lithium (10-100 ppm limit of detection), boron (500-1000 ppm limit of detection), and fluorine (1-10 ppm limit of detection), which are often difficult to determine by other analytical means. Because the technique is based upon specific nuclear reactions, the sensitivity of PIGE varies greatly from isotope to isotope, and this non-uniformity of sensitivity has limited its widespread use as a complementary technique to micro-PIXE. 

Abstract. AGB stars, in particular those of carbon types, are excellent laboratories to constraint the theory of stellar structure, evolution and nucleosynthesis. Despite the uncertainties still existing in the chemical analysis of these stars, the determination of the abundances of several key species in their atmospheres (lithium, s-elements, carbon and magnesium isotopic ratios etc.) is an useful tool to test these theories and the mixing processes during the AGB phase. This contribution briefly review some recent advances on this subject. 

Wiernik and Amiel [411] used neutron activation analysis to measure lithium and its isotopic composition in Dead Sea brines. 

Early workers had to strnggle with serious lithium fractionation effects during mass spectrometric analysis. Today most workers use the multicollector sector ICP-MS technique first described by Tomascak et al. (1999). Improvements of the analytical techniques in recent years have lead to an accuracy better than 0.3%o. Unfortunately, there are no internationally accepted Li isotope values for rocks or waters. James and Palmer (2000) have determined nine international rock standards ranging from basalt to shale relative to the so-called NIST L-S VEC standard. 

Germanium metal is also used in specially prepared Ge single crystals for y-ray detectors (54). Both the older lithium-drifted detectors and the newer intrinsic detectors, which do not have to be stored in liquid nitrogen, do an excellent job of spectral analysis of y-radiation and are important analytical tools. Even more sensitive Ge detectors have been made using isotopically enriched Ge crystals. Most of these have been made from enriched 7<5Ge and have been used in neutrino studies (55—57). 

In this chapter the focus is on a few structures that serve to highlight the key factors controlling the structures of chiral lithium amides in general. For a complete review on structures of lithium amides there are a number of excellent articles5-10. The structures of the chiral lithium amides discussed herein have been determined either by X-ray analysis or by multinuclear NMR spectroscopy of isotopically labelled compounds. The basics of lithium amide structures and in particular the structures and dynamics of chiral lithium amides will be presented. 

Analysis. The analytical system used for gamma-ray measurements consisted of a lithium drifted germanium (GeLi) crystal detector, a 4096 multi-channel analyzer, a PDP 11 computer, and a cassette magnetic tape storage. The germanium detector crystal has a volume of 55 cm with FWHM resolution of 2.3 keV at 1.33 MeV. The computer was used to analyze the gamma ray spectra, to identify the radio isotopes, and to calculate the concentration (Table III). 

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