Preparation of Trimethoprim Molecularly Imprinted Stir Bar Sorptive Extraction and Its Application for Trace Analysis of Trimethoprim and Sulfonamides in Complex Samples

Trimethoprim molecularly imprinted polymer (MIP) was prepared as the coating of stir bar sorptive extraction (SBSE) and applied to the trace analysis of trimethoprim and three sulfonamides in complex samples. The MIP-coating was about 21.5 μm thickness with the relative standard deviations (RSD) of 5.9% (n = 10). It was homogeneous and dense with good thermal and chemical stability. The extraction capability of the MIP-coating was 1.7 times over that of the non-imprinted polymer (NIP) coating. The MIP-coating exhibited selective adsorption ability to sulfonamides, triazines and methotrexate besides antibacterial synergists. The methods for the determination of trimethoprim and three sulfonamides by MIP-coated stir bar sorptive extraction coupled with HPLC were developed. It was successfully applied to the trace trimethoprim analysis in spiked urine and plasma samples. The linear range was 5-200 μg L−1 and the detection limit was 1.6 μg L−1. The recoveries in urine and plasma samples were 84.5% to 91.7% with RSDs of 2.9%–4.4%, 71.9% to 85.1% with RSDs of 3.0%–7.3%, respectively. The trimethoprim MIP-coated stir bar was also applied to the trace sulfonamides analysis in spiked milk sample. The linear range was 10–200 μg L−1, the detection limit was within the range of 4.5–6.1 μg L−1, and the recovery was 83.2%–110.2% with RSDs of 4.1%–8.0%.