A molecularly imprinted solid phase extraction (MISPE) method was developed for the rapid screening of cephalexin in human plasma and serum. The method employed a micro-column packed with molecularly imprinted polymer (MIP) particles for the selective solid phase extraction (SPE) of cephalexin. Since the MIP interacted indiscriminately with two other α-aminocephalosporins, cefradine and cefadroxil, their removal was ultimately achieved using differential pulsed elution (DPE) with acetonitrile+12% acetic acid. Cephalexin was then determined in a final pulsed elution (FPE) with methanol+1% trifluoroacetic (CF 3COOH, TFA) acid. This excellent selectivity represents a significant advance in analytical separation, demonstrating how a MIP can differentiate between molecules that are structurally dissimilar only in their non-hydrogen-bonding moieties, even if their hydrogen-bonding moieties are identical to each other. With UV detection, a concentration detection limit of 0.1μg/ml (or 2ng in 20μl) was afforded for cephalexin. By increasing the CHCl 3 flow rate to 1.25ml/min, each MISPE-DPE-FPE analysis required only 2min to complete. Rapid screening was demonstrated in a modified MISPE-PE method, which used 14% CH 3COOH+CH 3CN as the mobile phase, followed by direct PE with 1% TFA+CH 3OH.

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Analytica Chimica Acta
Department of Chemistry

Lai, E.P.C, & Wu, S.G. (Stanley G.). (2003). Molecularly imprinted solid phase extraction for rapid screening of cephalexin in human plasma and serum. Analytica Chimica Acta, 481(2), 165–174. doi:10.1016/S0003-2670(03)00087-4