Analysis of wheat extracts for ochratoxin A by molecularly imprinted solid-phase extraction and pulsed elution

A molecularly imprinted solid-phase extraction (MISPE) method has been developed for the rapid analysis of wheat extracts for ochratoxin A (OTA). Molecularly imprinted polymer (MIP) particles were synthesized from N-phenylacrylamide (PAM) and slurry-packed into a micro-column for selective solid-phase extraction (SPE) of OTA. With water flowing at 0.5 mL min(-1), a total binding capacity of 30 ng OTA was determined for the 20 mg of MIP particles. MISPE conditions were optimized using OTA in methanol/acetic acid (99:1 v/v). Nearly 100% binding could be achieved from one 20-muL injection of sample containing up to 30 ng of OTA. Pulsed elution (PE) using methanol/triethylamine (99:1 v/v) was good for the quantitative desorption of OTA. The MISPE-PE method, with fluorescence detection at lambda(ex)=385 nm and lambda(em)=445 nm, afforded a detection limit of 5.0 ng mL(-1) (or 0.1 ng in 20 muL of sample injected) for OTA. Recovery of OTA from wheat extracts was 103+/-3%. Each MISPE-PE analysis required less than 5 min to complete.