Trace analysis of aminoglycoside antibiotics in bovine milk by MEKC with LIF detection.

This work describes a straightforward and sensitive method for the multi-residue analysis of aminoglycoside antibiotics (kanamycin B, amikacin, neomycin B and paromomycin I) in bovine milk samples. The method involves the pre-capillary derivatization of antibiotics with sulfoindocyanine succinimidyl ester (Cy5) and their separation and determination by MEKC with LIF detection. The optimum procedure includes a derivatization step of the antibiotics at 25 degrees C for 30 min and direct injection for MEKC analysis, which is performed in about 20 min by using borate buffer (35 mM; pH 9.2) with 55 mM SDS as an anionic surfactant and 20% ACN as the organic modifier. Under these conditions, dynamic ranges of 10-500 microg/L and RSDs (within-day precision) from 3.8 to 5.3% were obtained. These results indicate that the proposed MEKC-LIF method is useful as a selective and sensitive tool for the determination of these antibiotics and surpasses other reported electrophoretic alternatives. Finally, the method was successfully applied to bovine milk samples after a simple solid-phase extraction clean-up and preconcentration procedure. The aminoglycosides were readily detected at 0.5-1.5 microg/kg levels with average recoveries ranging from 89.4 to 93.3%.