Off-campus South Dakota State University users: To download campus access theses, please use the following link to log into our proxy server with your South Dakota State University ID and password.

Non-South Dakota State University users: Please talk to your librarian about requesting this thesis through interlibrary loan.

Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)

Department / School


First Advisor

James A. Rice


A procedure for extracting humic acid from soils using tributyl phosphate (TBP) is described. Humic acids were isolated from a cultivated Minnesota garden (MG) soil (Aquic Haploborolls) and the International Humic Substances Society (IHSS) reference soil (Aquic Argindolls), and were characterized with respect to their elemental compositions, acidic functional group contents, and IR and C-13 NMR spectra. These characteristics are compared to those of the humic acids isolated from the· same soils by the methylisobutyl ketone (MIBK) method and traditional alkali extraction procedure. The effectiveness of TBP as an extraction solvent for humic acid was comparable to that of the traditional alkali extraction method. The TSP humic acid exhibited a lower N content, higher P content and higher acidic functional group content than either of the other two humic acids isolated from the same soil. Reasons for these differences are discussed.

Library of Congress Subject Headings

Soils -- Humic acid content -- Analysis
Tributyl phosphate
Solvent extraction
Soils -- Analysis



Number of Pages



South Dakota State University