LIQUID-CHROMATOGRAPHIC MASS-SPECTROMETRIC DETERMINATION OF 1-AMINOCYCLOPROPANE-1-CARBOXYLIC ACID IN TOBACCO

Liquid chromatography-thermospray mass spectrometry was investigated as a method for determination of 1-aminocyclopropane-1-carboxylic acid (ACC) in Nicotiana tabacum cv. Petit Havana SR1. A stable isotope analogue of ACC ([H-2(4)]ACC) was used as an internal standard. The internal standard was added to the plant samples prior to extraction. After solid-phase extraction both ACC and [H-2(4)]ACC were derivatized with phenyl isothiocyanate (PITC) to the corresponding phenylthiohydantoin compounds PTH-ACC and [H-2(4)]PTH-ACC. Selected ion monitoring of the protonated molecules [MH](+) of m/z 219 and 223 was used for quantification. The method is sensitive and highly specific for the determination of ACC in plant extracts. This in contrast with the assay Lizada and Yang, which in several instances overestimated ACC in tobacco, probably owing to the presence of one or more interfering compounds.