Rapid and sensitive determination of trace fluoroquinolone antibiotics in milk by molecularly imprinted polymer-coated stainless steel sheet electrospray ionization mass spectrometry.

Rapid analysis of trace analytes in complex biological samples is a great challenge for direct mass spectrometry, which suffers from low detection sensitivity. In this study, molecular imprinting technology was explored on the stainless steel sheet and integrated with the electrospray ionization method for direct sample analyses. The molecularly imprinted polymer-coated stainless steel sheet (MIPCS) was prepared and used as a solid-phase microextraction tip for rapid sampling of trace fluoroquinolone antibiotics in milk samples and then applied as an electrospray ionization tip to couple MS for sensitive detection. Our results shown that MIPCS could significantly enrich the trace fluoroquinolone antibiotics in milk samples. In our study, the extraction process of milk sample was completed within 30 min and the direct MS analysis was accomplished within 1 min. In addition, this proposed MIPCS-ESI-MS method showed a good linearity (R2>0.99) ranged from 1 to 1000 ng mL-1. The limits of detection (LODs) and limits of quantitation (LOQs) for the analytes range from 0.1 to 5 ng mL-1. The recoveries were in a range of 78.84%-103.04%. The relative standard deviation (RSD%) of inter-day and intra-day precision ranged from 7.00% to 10.4% and 4.46%-11.44% respectively. Overall, the proposed MIPCS-ESI-MS method could be feasibly used as a rapid and sensitive method for determination of trace analytes in complex food samples.