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We compared the recently developed surfactant-based extraction with sodium bis-[2-ethylhexyl]-sulphosuccinate (AOT) in heptane (the phase-transfer method) and the well established methodology with poly(oxyethylene)-7,5-(p-tert-octylphenyl) ether (Triton X-114; the cloud-point technique) to extract and preconcentrate biogenic amines. Both procedures were optimized and applied to the extraction of biogenic amines from a beer sample. In order to improve the degree and monitoring of the extraction otherwise achieved with underivatized amines, the fluorescent reagent dansyl chloride was used. Since the different procedures described in the literature are not in agreement, we optimized the derivatization reaction. Accordingly a systematic investigation of the experimental variables, one by one, yielded the following optimum conditions: dansyl chloride, 5mg/mL; 27 degrees C; reaction time, 25min; pH, 10.35 at ionic strength, 0.7mol/L. Both surfactant-based extraction procedures are simple and sensitive, but the use of AOT instead of Triton X-114 offers certain advantages. Detection limits of between 0.03 and 0.8pmol injected were obtained when AOT was used, whose range is similar to or better than the other published techniques; while the corresponding values for Triton X-114 were between 0.2 and 1.2pmol injected. The phase-transfer extraction is faster than the cloud-point method, and no heating is required. For both approaches, the recovery was very high for all the amines studied and the reproducibility quite good for almost all. Upon comparison of calibration curves in pure water with those in the presence of samples, matrix effects were detected.

Abstract: The ability of reverse microemulsions of the surfactant bis [2-ethylhexyl] sulphosuccinate (AOT) in heptane to extract and preconcentrate eight biogenic amines present in aqueous matrices has been explored. The “phase transfer” method, in which the surfactant solution is contacted with an aqueous salt solution containing the analytes, has been used as the analytical methodology. The extraction efficiencies have been compared with those obtained by using the “cloud point” extraction technique with Triton X-114 as surfactant, and with methylene chloride as a typical extracting solvent. In order to improve extraction and detection as compared with the underivatized amines, the fluorescent reagent dansyl chloride has been used to obtain the more hydrophobic and thus, easily extractable dansyl derivatives. Although extraction of most of the biogenic amines is high, extraction of their dansyl derivatives is practically 100%. The procedure was successfully applied to the analysis of commercial fruit juices. The analytical methodology is sensitive, fast, simple and reproducible. The LOD were in the vicinity of 1 and 2pmol, which is similar or better than other techniques. The micellar phase is compatible with reverse phase HPLC mobile phases, which allow direct injection of the analyte after extraction. This is an advantage over solid phase extraction (SPE), where incomplete recovery can occur. Moreover, AOT showed to be better extracting surfactant for biogenic amines (and their corresponding dansyl derivatives) than Triton X-114 at the same concentration. [Copyright &y& Elsevier]