Determination of Boron in Biological Samples

Two sample treatment methods are evaluated to provide accurate boron determination at low concentrations in biological and botanical samples. The first approach is a hot 1M nitric acid extraction of boron from the sample. The second technique uses wet digestion with concentrated sulfuric acid. The accuracy of the procedures was demonstrated with botanical and animal reference materials (Corn Bran RM 8433 and Whole Egg Powder RM 8415). At least three results are given for each reference material. Two are direct measurements of B using independent ¹⁰B and ¹¹B calibration curves with a Be internal reference, and the third is obtained by isotope dilution mass spectrometry (IDMS). The ¹⁰B and ¹¹B values are consistent for both acid treatment procedures. The IDMS results also are consistent. Overall results for Whole Egg Powder and Corn Bran RM's match the best-estimate values within their confidence intervals. These results demonstrate the ability to measure B accurately at the 0.3 µg/g concentration range. Thus, low-level B samples can be analyzed with accuracy and precision by the two approaches. These methods introduce very little dissolved organic carbon (DOC) in the final solution and allow the use of large (2 g) sample aliquots. Direct introduction of biological fluids including whole blood serum also was evaluated critically for the determination of B.