A technique to facilitate diffusions for nitrogen-isotope analysis by direct combustion
- K. K. Moran,
- R. L. Mulvaney * and
- S. A. Khan
A technique was developed that permits the use of boric acid-indicator solution in carrying out diffusions for inorganic 15N analysis of soil extracts by direct combustion, so as to eliminate the need for a separate quantitative determination. In this technique, the titrated sample is acidified with 2.5 M KHSO4 and subsequently treated with methanol to remove H3BO3 The NH+ 4-N is dissolved in 1 mL of deionized water, concentrated after transfer to a microcentrifuge tube, and freeze-dried in a tin capsule. Isotope-ratio analyses were accurate to within 5% when diffusions were performed on 100 to 1000 μg of NH+ 4-N (0.2–10 atom % 15N), whereas errors of 8 to 17% occurred with 25 to 50 μg of labeled N, even after correction for isotopic dilution by atmospheric NH3 The technique described permits 15N analysis of any form of N that can be recovered by H3BO3 diffusion of soil, soil extracts, soil hydrolysates, Kjeldahl digests, water, or wastewater.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
Copyright © 2002.