Ion-pair solid-phase extraction of biogenic amines before micellar electrokinetic chromatography with laser-induced fluorescence detection of their fluorescein thiocarbamyl derivatives

Extraction conditions by ion-pair solid-phase extraction of biogenic amines from soy sauce samples were studied. The type of surfactant used as ion-pair reagent, the mode of extraction and the pH were factors studied to enhance the extraction efficiency. High recoveries were obtained using dodecylbenzenesulfonic acid as ion-pair reagent. Octanesulfonate and decanesulfonate did not provide satisfactory recoveries. A dynamic ion-pair solid-phase extraction method was also tested for comparison. The extracted amines were derivatized with fluorescein isothiocyanate, separated by micellar electrokinetic chromatography and detected by laser-induced fluorescence (MEKC-LIF). Because of sample clean-up after extraction and the very high number of theoretical plates obtained with the MEKC-LIF method, identification and quantification of biogenic amines in soy sauce samples could be accomplished. Biogenic amines in soy sauce samples could be separated and quantified with detection limits of the order of 0.1 microg/mL, depending on the sample source.