Miniaturized graphene-based pipette tip extraction coupled with liquid chromatography for the determination of sulfonamide residues in bovine milk.

A miniaturized graphene-based pipette tip extraction (M-G-PTE) method coupled with liquid chromatography-ultraviolet detection was developed for rapid screening of sulfadimidine, sulfachloropyridazine, sulfamonomethoxine, and sulfachloropyrazine residues in bovine milk. Because of the large surface area and unique chemical structure of graphene, an M-G-PTE device packed with 3.0mg graphene could handle 2.0mL of milk samples at one time. This M-G-PTE device showed better adsorption performance for sulfonamides (SAs) than those packed with other adsorbents such as C18, HLB, SCX, PCX, and multiwalled carbon nanotubes. Under the optimized conditions, good linearity was obtained in the range of 0.05-6.0 μg g(-1), with a correlation coefficient (r(2)) of ⩾0.9991. The recoveries at three spiking levels ranged from 90.1% to 113.5% with relative standard deviations (RSDs) of ⩽3.9%. The proposed M-G-PTE method was simple, economical, sensitive, and produced less organic pollution. Thus, it could be applied to the rapid screening of SAs in complicated bovine milk samples.