High-precision measurement of variations in calcium isotope ratios in urine by multiple collector inductively coupled plasma mass spectrometry

Jennifer L L Morgan, Gwyneth Gordon, Ruth C. Arrua, Joseph L. Skulan, Ariel Anbar, Thomas D. Bullen

Research output: Contribution to journalArticle

37 Scopus citations

Abstract

We describe a new chemical separation method to isolate Ca from other matrix elements in biological samples, developed with the long-term goal of making high-precision measurement of natural stable Ca isotope variations a clinically applicable tool to assess bone mineral balance. A new two-column procedure utilizing HBr achieves the purity required to accurately and precisely measure two Ca isotope ratios ( 44Ca/ 42Ca and 44Ca/ 43Ca) on a Neptune multiple collector inductively coupled plasma mass spectrometer (MC-ICPMS) in urine. Purification requirements for Sr, Ti, and K (Ca/Sr > 10000; Ca/Ti > 10000000; and Ca/K > 10) were determined by addition of these elements to Ca standards of known isotopic composition. Accuracy was determined by (1) comparing Ca isotope results for samples and standards to published data obtained using thermal ionization mass spectrometry (TIMS), (2) adding a Ca standard of known isotopic composition to a urine sample purified of Ca, and (3) analyzing mixtures of urine samples and standards in varying proportions. The accuracy and precision of δ 44/42Ca measurements of purified samples containing 25 μg of Ca can be determined with typical errors less than ±0.2 (2σ).

Original languageEnglish (US)
Pages (from-to)6956-6962
Number of pages7
JournalAnalytical chemistry
Volume83
Issue number18
DOIs
StatePublished - Sep 15 2011

ASJC Scopus subject areas

  • Analytical Chemistry

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