Dialkyl anionic surfactant in field-amplified sample injection and sweeping-micellar electrokinetic chromatography for determination of eight leanness-promoting β-agonists in animal feeds.

The beta-adrenergic agonists (β-agonists) working as repartitioning agents that make the carcass leaner and enhance the feeding efficiency in animals have been banned in the European Union, China and Taiwan. Here, traditional anionic surfactants, such as sodium dodecyl sulfate (SDS) were replaced with sodium di-(2-ethylhexyl)-sulfosuccinate (AOT) in field-amplified sample injection and sweeping-micellar electrokinetic chromatography (FASI-sweeping MEKC) for simultaneous analysis of eight β-agonists in animal feeds. The AOT vesicles provided a better resolution of β-agonists than micelles of SDS. The detection limits of the eight β-agonists were above 5ng/mL by using this stacking capillary electrophoresis (CE) method. In comparison of traditional MEKC method (sample injection, 1psi for 5s), the stacking strategy provided 400-2000 fold sensitivity enhancement. After method validation, this method was successfully applied for analyzing four animal feeds, and none β-agonist was detected. This strategy possessing good resolution of eight β-agonists was suitable for serving as a tool for routine analysis of animal feeds.