Fiber-in-tube solid-phase microextraction with molecularly imprinted coating for sensitive analysis of antibiotic drugs by high performance liquid chromatography.

An on line fiber-in-tube solid-phase microextraction (SPME) method was developed by longitudinally packing molecularly imprinted fibers (MIP-fibers) into PEEK tube as the online extraction unit. The obtained device therefore offers a reduced back pressure and rapid kinetics for its longitudinal channels, as well as possesses improved extraction capacity compared with traditional SPME method thanks to the increase of coating volume. In addition, the extraction of analytes was specific by using molecularly imprinted coatings, which greatly reduced the interference of sample matrix. To evaluate the new strategy, the PEEK tube was firstly packed with multiple ofloxacin imprinted fibers (OFL-MIP-fibers) for the analysis of four fluoroquinolones in animal-producing food samples. The extraction yields were significantly increased with the enrichment factors from 69 to 136. Sensitive results were achieved with the limits of detection as low as 0.016-0.11 μg/L (S/N=3). This method was applied successfully to analysis of fluoroquinolones in pork liver and chicken samples with good repeatability (RSDs less than 7.2%). To expand the method, the PEEK tube was then filling with two different fibers imprinted by ofloxacin and sulfamethazine respectively in order to obtain simultaneous extraction of these two categories of antibiotic drugs. Preliminary results showed the hybrid packing strategy could simultaneously enrich the target analytes from complicated samples. The possibility of applying the method to pork liver sample spiked with fluoroquinolones and sulfonamides was also studied.