Accelerator mass spectroscopy (AMS) can be used for efficient detection of long-lived isotopes at part-per-quadrillion sensitivities with good precision In this article we present an overview of AMS and its recent use in archaeology, geochemistry and biomolecular tracing All AMS systems use cesium sputter ion sources to produce negative ions from a small button of a solid sample containing the element of interest, such as graphite, metal halide, or metal oxide, often mixed with a metal powder as binder and thermal conductor Experience shows that both natural and biomedical samples are compatible in a single AMS system, but few other AMS sites make routine {sup 14}C measurements for both dating and tracing AMS is, in one sense, just `a very sensitive decay counter`, but if AMS sensitivity is creatively coupled to analytical chemistry of certain isotopes, whole new areas of geosciences, archaeology, and life sciences can be explored 29 refs, 2 figs, 1 tab

Accelerator Mass Spectrometry

The state of the art in accelerator mass spectrometry (AMS) is reviewed. The review is divided in two parts. The first covers the general methodology, followed by its specific elaborations for the commonly measured long-lived isotopes such as 10Be, 14C, 26Al, 36Cl and 129I, as well as other isotopes with emerging applications. The second part considers the very wide spectrum of applications that now employ AMS, and groups these according to research area rather than isotope. The period up until late 1998 is covered, with an emphasis on post-1990 developments and literature.

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Accelerator mass spectrometry and its applications

Progress in isotope analysis at ultra-trace level by AMS

Applications of accelerator mass spectrometry

Calcium metabolism in biology may be better understood by the use of 41Ca tracer, although requiring detection by accelerator mass spectrometry (AMS). Methodologies for preparation of urine samples and subsequent AMS measurement were investigated. Novel attempts at preparing CaH2 were unsuccessful, but CaF2 of sufficient purity could be produced by precipitation of calcium from urine as oxalate, followed by separation of calcium by cation exchange chromatography and washing the CaF2 precipitate. The presence of some remaining impurities could be compensated for by selecting the appropriate accelerated ion charge state for AMS. The use of projectile X-rays for isobar discrimination was explored as an alternative to the conventional d E d x detector.

Biological sample preparation and 41Ca AMS measurement at LLNL

We are investigating long- and short-term processes that involve the resorption of the bone calcium in the human body, using accelerator mass spectrometry of 41Ca ( T 1 2 = 104000 years). The evolution of an injected dose of 41Ca has been followed over 900 days by measurements in urine and serum. The 41 Ca/Ca isotopic ratio rapidly decreased after injection and after about 100 days, reached a quasi-steady state of 1.5 × 10−11. Variations in this level would signal a change in rates of calcium resorption from the bone.

Calcium resorption from bone in a human studied by 41Ca tracing

The mechanisms governing calcium fluxes during bone remodeling processes in perimenopausal women are poorly known. Despite higher, albeit erratic, estradiol levels in perimenopause, spine bone loss is greater than during the first five years past the final menstrual flow when estradiol becomes low. Understanding changes during this dynamic transition are important to prevent fragility fractures in midlife and older women. The exploration of long-lived 41 Ca ( T 1/2  = 1.04 × 10 5  yrs) tracer measurements using accelerator mass spectrometry (AMS) leads to the possibility of monitoring bone remodeling balance. With this new technology, we explored a pilot long-term feasibility study of bone health by measuring the 41 Ca trace element in urine for six years from premenopausal to later perimenopausal phases in one midlife woman. We measured bone mineral density in parallel.

J. Prior

Papers

Calcium resorption from bone in a human studied by 41Ca tracing

A pilot study of the feasibility of long-term human bone balance during perimenopause using a 41Ca tracer