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The isotopic analysis of boron has been carried out using dflerent pairs of isotopic Li2BO: ions as monitors. The precision of the mass spectrometric measurements of different molecular abundance ratios is roughly the same. However, the values of the '%/"B abundance ratio calculated from the experimental ratios of different pairs of isotopic molecular ions show large variations. These variations are shown to be a logical consequence of the calculation step which leads to the magnification of measurement errors to different extents for different peak ratios. Similar arguments would apply for the isotopic analysis of any element employing the molecular ion beam technique. The effect of isotopic fractionation on the molecular abundances is also discussed. The important implication of the present investigation is that it sets the guidelines for selecting suitable monitor molecules to avoid such errors.Molecular ion beams are sometimes employed for the isotopic analysis of elements. ' -12 The related analytical procedure is, by and large, comparable to the conventional atomic ion beam method of isotopic analysis. However, the molecular ion beam method involves (barring those cases where all other constituents of the chosen molecule except the element of interest are monoisotopic) calculations of elemental isotopic abundance ratio(s) from the experimentally measured molecular ion ratio(s) using known isotopic abundance values of the other constituent elements. The central theme of this paper is to pay attention to this calculation step. This is because the calculation process may either enhance or even reduce the error in isotopic analysis due to error propagation, as indicated in Ref.12 which dealt with the determination of the 6Li/7Li abundance ratio using the Li2B02 molecule with all constituent isotopes at their natural isotopic abundance. It was demonstrated" that the precision of the measurements of the intensity ratio of the most abundant Li,BO: ions (mlz 56 and 57) is better than 0.1% , while the uncertainty in the value determined for the 6Li/7Li abundance ratio is 0.3%. The present work involves the isotopic analysis of a "B-enriched isotopic reference material of boron, SRM-952. This was chosen with a view to examining whether the selection of the most abundant Li,BO: ions as monitors also ensures accurate isotopic analysis of a constituent element whose isotopic abundance ratios are quite different from the natural ratios. This paper presents the loB/'lB abundance ratios determined using the experimental intensity ratios of different pairs of isotopic molecular ions and discusses the differences in the results so obtained. EXPERIMENTALThe instrument used is a thermal ionization mass spectrometer, model 261 (Finnigan MAT, Bremen, Germany), upgraded for simultaneous collection of separated ion beams.Author to whom correspondence should be addressed.The lithium sample used for this work was Li2C03, a natural isotopic standard of lithium Svec with certified 6Li/7Li abundance ratio of 0.0832 k 0.0002. l3 The ...

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Precision /Accuracy IDetermination of^'Pu/(^^^Pu + ^^'Pu) / Alpha spectrometryO.Ol to 10 by a spectrometry and demonstrates the validity of a simple method for the analysis of a spectrum. AbstractThe evaluation of precision and accuracy in "'Pu/("'Pu+""'Pu) a activity ratio determination is of paramount importance for calculating '"Pu in plutonium samples and for exploiting Isotope Dilution Alpha Spectrometry (IDAS) to establish the concentration of plutonium in the irradiated fuel dissolver Solution. This has been achieved by preparing synthetic mixtures with a activity ratios ranging from O.Ol to 10 using '"Pu and '"Pu isotopes. Sources were prepared from these mixtures by electrodeposition in an aqueous HNO3 medium and the a spectra were recorded by employing a solid State sihcon surface barrier detector coupled to a 4 K analyser. The validity of a simple evaluation method based on the geometric progression (G. P.) decrease for the far tail of the spectrum is demonstrated in the present work. It is concluded that an accuracy of 0.5% and a precision of ± 0.2% (1 o) can be reached in the determination of "»Pu / ("' Pu+"° Pu) cx activity ratio ranging from O.Ol to 10.