Environmental Health Perspectives 102, Supplement 7, November 1994

[Citation in PubMed]

Use of Inductively Coupled Plasma-Mass Spectrometry in Boron-10 Stable Isotope Experiments with Plants, Rats, and Humans

Richard A. Vanderpool¹, Deb Hoff¹, and Phyllis E. Johnson²

¹United States Department of Agriculture, Agricultural Research Service, Grand Forks, North Dakota;
²United States Department of Agriculture, Agricultural Research Service, Albany, California

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Abstract
The commercial availability of inductively coupled plasma-mass spectrometry technology (ICP-MS) has presented the opportunity to measure the boron concentrations and isotope ratios in a large number of samples with minimal sample preparation. A typical analytical sequence for fecal samples consists of 25 acid blanks, 1 digestion blank, 5 calibration solutions, 4 standard reference material solutions, 10 samples, and 4 natural abundance bias standards. Boron detection limits (3 1) for acid blanks are 0.11 ppb for ¹⁰B, and 0.40 ppb for ¹¹B. Isotope ratios were measured in fecal samples with 20 to 50 ppb boron with <2% relative standard deviation. Rapid washout and minimal memory effects were observed for a 50 ppb beryllium internal standard, but a 200 ppb boron biological sample had a 1.0 ppb boron memory after a 6-min washout. Boron isotope ratios in geological materials are highly variable; apparently this variability is reflected in plants. The lack of a fixed natural abundance value for boron requires that a natural abundance ratio be determined for each sample or related data set. The natural abundance variability also prevents quantitation and calculation of isotope dilution by instrument-supplied software. To measure boron transport in animal systems, 20 µg of ¹⁰B were fed to a fasted rat. During the 3 days after a ¹⁰B oral dose, 95% of the ¹⁰B was recovered from the urine and 4% from the feces . Urinary isotope ratios, ¹¹B/¹⁰B, changed from a natural abundance of 4.1140 to an enriched value of 0.9507, a 77% change. The ¹⁰B label in perfused rat livers peaked within 3 hr (>90% recovery, 56% change in ¹¹B/¹⁰B) and returned to a natural abundance ratio within 24 hr. In summary, boron concentrations and enriched isotope ratios have been measured successfully in rat urine and feces by using ICP-MS. -- Environ Health Perspect 102(Suppl 7):13-20 (1994)

Key words: ICP-MS, ¹⁰B, memory, stable isotopes, matrix, beryllium, boron

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This paper was presented at the International Symposium on Health Effects of Boron and Its Compounds held 16-17 September 1992 at the University of California, Irvine, California.

Address correspondence to Dr. Richard A. Vanderpool, USDA, ARS, GFHNRC, PO Box 7166, University Station, Grand Forks, ND 58202-7166. Telephone (701) 795-8416. Fax (701) 795-8395.

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