Vortex-assisted liquid–liquid microextraction coupled with derivatization for the fluorometric determination of aliphatic amines

Abstract

A new one-step derivatization and microextraction technique was developed for the fluorometric determination of C1–C8 linear aliphatic primary amines in complex sample solutions containing high levels of amino acids. In this method, amines were derivatized with o-phthalaldehyde (OPA) and 2-mercaptoethanol (2-ME) in aqueous solution and extracted simultaneously by vortex-assisted liquid–liquid microextraction (VALLME). Parameters affecting the extraction efficiency were investigated in detail. The optimum conditions were as follows: 50μL of isooctane as the extractant phase; 2.0mL aqueous donor samples with 12mM OPA, 24mM 2-ME, and 0.1M borate buffer at pH 10; 1min vortex extraction time; centrifugation for 4min at 6000rpm. After centrifugation, the enriched analytes in the floated extractant phase were determined by HPLC–FL in less than 14min. Under the optimum conditions, the limits of detection were of the order of 0.09–0.31nM. The calibration curves showed good linearity over the investigated concentration range between 0.4 and 40nM. The proposed method has been applied to the determination of aliphatic amines in acidophilus milk, beer, and Cu(II)/amino acid solution.