Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 10/25/2001
Publication Date: 10/25/2001
Citation: GONZALEZ, J.M., LAIRD, D.A. AMINO ACID ANALYSIS OF SOIL CLAY FRACTIONS BY RP-HPLC. AGRONOMY ABSTRACTS. 2001. CD-ROM. MADISON, WI. ASA-CSSA-SSSA.
Technical Abstract: Amino acids are hypothesized to be significant components of humified soil organic matter (SOM) and to contribute to both biological N availability and SOM stabilization. Specific objectives of this study were to develop a RP-HPLC UV-Vis detection technique for analysis of amino acids in SOM and to quantify the amino acid composition of humified SOM associated with clay fractions isolated from three soils. Surface horizon samples of Webster soil were collected from sites with soybean, corn and prairie vegetation. The samples were fractionated by sedimentation to isolate the whole clay (<2 um) and by ultrasonic dispersion and centrifugation to isolate the coarse (0.2-2 um), medium (0.02-0.2 um), and fine (<0.02 um) clay fractions. The samples were hydrolyzed for 16 h with 4 M methanesulfonic acid in acid digestion bombs. An aliquot of the hydroslate was neutralized (pH =8.5 to 9.0) and reacted with excess dabsyl chloride at 70 C for 10 min. Amino groups react with the sulfonyl chloride moiety of the dabsyl to form a stable sulfonamide that can be separated by RP-HPLC and detected by UV-Vis spectroscopy. Amino acids in the studied clay fractions accounted for 5 to 13% of the total C and 29 to 60% of the total N. Amino acid content was greatest in the soil with prairie vegetation and lest in the soil with soybean vegetation. For all three soils, the fine clay had substantially more amino acids than the coarse clay fraction. Arginine was the most abundant amino acid accounting for 21 to 32% of total amino acid N in the samples.