Extraction of amino acids from aqueous solution with dithiophosphinates

A method for recovering monocarboxylic amino acids free of hydroxy groups from aqueous solutions thereof which comprises contacting such a solution with a sufficient amount of a dithiophosphinate having the formula:

• ##STR2## wherein each R, individually, is an alkyl or cycloalkyl radical of 4-18 carbon atoms, inclusive, an aryl radical of 6-18 carbon atoms, inclusive, an aralkyl radical of 7-20 carbon atoms, inclusive, or both Rs, together with the phosphine atoms, form either a 5 or 6 membered ring which may contain oxygen, or a bicyclic radical, and R.sup.1 is hydrogen or a cation, in the presence of an organic diluent which forms a substantially water-insoluble liquid when in contact with the dithiophosphinate under extraction conditions to extract said amino acid and separating the extracted solution from said dithiophosphinate.