Determination of 1-aminocyclopropane-1-carboxylic acid and its structural analogue by liquid chromatography and ion spray tandem mass spectrometry

Liquid chromatography coupled to ion spray tandem mass spectrometry was dev eloped as a method for the simultaneous analysis of the amino acid 1-aminoc yclopropane-1-carboxylic acid (ACC) and its structural analogue, cyclopropa ne-1,1- dicarboxylic acid (CDA). ACC and CDA fragmentation as well as optim ization of MS parameters were investigated in positive ion mode. In selecti ve reaction monitoring mode the protonated molecule [M+H](+) was selected a s parent ion for both ACC and CDA, while the immonium ion from ACC and the [M+H-H2O](+) ion from CDA were selected, respectively, as product ions. In spite of the high selectivity of MS/MS among the 20 protein amino acids pot entially present with ACC and CDA in the plant material analyzed, Glu and T hr can interfere with the signal of ACC. As a result, their chromatographic separation is necessary. This was achieved in less than 4 min by ion-pair reversed-phase chromatography with nonafluoropentanoic acid as ion-pair rea gent. A linear response within a concentration range of 1-5 mg l(-1) was ob served for this LC method and the detection limit was found to be 20 pmol f or ACC and 150 pmol for CDA (using a 20-mul loop). This methodology was suc cessfully applied to the detection of ACC in apple tissue. (C) 2000 Elsevie r Science B.V. All rights reserved.