A technique to recover tracer as carboxyl-carbon and alpha-nitrogen from amino acids in soil hydrolysates.
Isotope analysis of biochemical compounds provides an unequivocal means for detecting assimilation of tracer C and N into microbial biomass. A diffusion method recently developed to determine amino acid-N by ninhydrin oxidation of soil hydrolysates was modified to permit simultaneous collection of the CO2 liberated during this oxidation. In the technique described herein, this is accomplished after removal of (NH4+ + amino sugar)-N, by performing ninhydrin oxidation at 90 degrees C for 7 h in a 1.9 L Mason jar sealed with a lid equipped to support a petri dish containing 5 mL 0.2N NaOH. Recoveries of carboxyl-C and alpha-N ranged from 98 to 101% in evaluations with standard solutions of amino acids, whereas these recoveries exceeded 90% for 14C and 94% for 15N when soil hydrolysates amended with labeled amino acids were analyzed.
Marsh
Kerri L
KL
University of Illinois, Department of Natural Resources and Environmental Sciences, Urbana, IL 61801, USA.
Mulvaney
Richard L
RL
Sims
Gerald K
GK
D000409:Alanine / Q000032:analysis; D000596:Amino Acids / Q000032:analysis*; D002244:Carbon / Q000032:analysis*; D004058:Diffusion; D006868:Hydrolysis; D007202:Indicators and Reagents; D009555:Ninhydrin; D009584:Nitrogen / Q000032:analysis*; D015203:Reproducibility of Results; D012987:Soil / Q000032:analysis*
D000596:Amino Acids; D007202:Indicators and Reagents; D012987:Soil; D002244:Carbon; D009555:Ninhydrin; D009584:Nitrogen; D000409:Alanine