Molecularly imprinted polypyrrole modified carbon nanotubes on stainless steel frit for selective micro solid phase pre-concentration of ochratoxin A

A molecularly imprinted polymer (MIP) was prepared by electrochemical polymerization of pyrrole (Py) onto a stainless steel frit, using ochratoxin A (OTA) as the template and carbon nanotubes (CNTs) as nano-structured fibers, to make a micro-solid phase pre-concentration (μSPP) device. The OTA template was removed with 1% triethylamine in methanol. This μSPP device was coupled on-line to high performance liquid chromatography (HPLC) with fluorescence detection, using 20:80 v/v acetonitrile-ammonia buffer (20 mM NH4Cl/NH3, pH 9.2) as the mobile phase. MIPPy/CNT-μSPP-HPLC results clearly demonstrated a significant enhancement of selective binding capacity for OTA at sub-ppb levels even in the presence of abundant red wine matrix components. Using a sample volume of 3 mL red wine for pre-concentration, it was possible to determine OTA down to a detection limit of 12 ppt, or a quantification limit of 41 ppt. A larger sample volume of red wine for pre-concentration would further improve the quantification limit.