l-3- ( 3,4-dihydroxyphenyl ) alanine ( dopa ) and its 3-o-methyl metabolite ( omd ) were measured in plasma and cerebrospinal fluid by a new assay which combines n , o-acetylation of amino acids in aqueous media , preparation of pentafluorobenzyl esters under anhydrous conditions , and analysis by gas chromatography-electron capture negative ion mass spectrometry .
C0001898
alanine
C0002520
amino acids