Extraction of free amino acids from soil

Includes bibliographical references (page 198).Alternatives to extraction with ethanol were examined in order to obtain more effective removal of free amino acids from soil. Ba(OH)2 was a promising extractant and proved to be very effective in recovering a mixture of 17 amino acids that had been added to soil. Resolution of the extract by elution chromatography was followed by colorimetric analysis; 73 to 121% of the acidic and neutral components of the mixture and 36 to 41% of the basic amino acids were recovered. A second extraction procedure, based on the use of NH4OAc, was developed to avoid any slight hydrolysis of amino acid polymers that may have occurred during preparation of Ba(OH)2 extracts. The NH4OAc extraction procedure was 31 to 83% effective in the recovery of added amino acids from soil. When both extraction techniques were applied in preliminary trials to characterize the free amino acids fraction of a soil, the NH4OAc extraction was considered the better. Both NH4OAc and Ba(OH)2 extractions yielded many more kinds of free amino acids in concentrations 5 to 25 times greater than that reported earlier in comparable studies using ethanol extraction