Molecularly imprinted solid-phase extraction of cephalexin from water-based matrices

In the present paper, we describe the synthesis of a cephalexin (CFX) molecularly imprinted polymer (MIP), the direct application of the MIP to SPE for the determination of CFX (which is a -lactam antibiotic) in human urine and the use of the MIP in a tandem SPE system to determine CFX in river water. The molecularly imprinted polymers (MIP) showed cross-selectivity for amoxicillin (AMX; also a -lactam antibiotic). This allowed both CFX and AMX to be quantified in acidified human urine, with recoveries of 78 and 60% for CFX and AMX, respectively, when the urine samples were spiked with CFX and AMX at 4 mg/L. These analyses were facile because the molecularly imprinted solid-phase extraction (MISPE) extracts were clear compared to the nonpurified samples. In order to increase the sample volume for river water analyses, a tandem SPE system incorporating a commercially available sorbent was implemented. With this set-up, CFX was determined with recoveries in excess of 50% when 200 mL of acidified river water samples spiked at 10 g/L with CFX were percolated through the tandem system.