MEASUREMENT OF BORON CONCENTRATION AND ISOTOPE RATIOS IN BIOLOGICAL SAMPLES BY INDUCTIVELY COUPLED PLASMA MASS-SPECTROMETRY WITH DIRECT INJECTION NEBULIZATION

A method for the determination of boron in a variety of biological samples is described. Sample material is fused with sodium carbonate and boron is separated from matrix components by using Amberlite IRA-743 boron selective ion-exchange resin. Boron is eluted with 1% HNO3 and samples are introduced to an inductively coupled plasma mass spectrometer with a direct injection nebulizer. This nebulizer provides a fast sample cleanout of ca. 15 s. The B-10/B-11 ratio is determined with a relative standard deviation (RSD) of 0.4-1.5%, and the detection limit for boron is approximately 1 ng g-1 in these samples. Stable isotope dilution methodology for quantitation of boron shows that: (1) fusion of sample with sodium carbonate avoids volatilization of boron from samples; (2) approximately 80% of submicrogram amounts of boron from samples can be recovered from the resin with insignificant isotopic fractionation; (3) results for biological reference materials are in agreement with certified values; and (4) the boron concentration of pooled human blood plasma is 24 +/- 4-mu-g l-1 (95% confidence interval).