Development of polypyrrole films by electrochemical imprinting for molecular recognition of ochratoxin A: Applications in surface plasmon resonance sensor and micro solid phase extraction

This thesis describes research on a new electrochemical imprinting technique, in which pyrrole was used as a functional monomer for the preparation of molecularly imprinted polymers (MIPs). The molecularly imprinted polypyrrole (MIPPy) was electrochemically deposited onto the substrate from a pre-polymerization mixture containing ochratoxin A (OTA) as the template molecule. After removal of OTA templates, the binding properties of MIPPy were characterized by surface plasmon resonance (SPR), and high performance liquid chromatography (HPLC). Applications of the MIPPy were to serve as the sensing element for SPR and as the selective sorbent coating the pores of a stainless steel frit to make a novel micro solid phase extraction (muSPE) device.; For sensor development, a MIPPy film was synthesized in situ onto a miniaturized SPR sensor. Film growth of MIPPy and subsequent binding event were monitored by the SPR angle (thetar). Sensor performance was investigated by running OTA standard solutions into the integrated 20 muL flow cell. After 300 seconds, nonlinear regression was used to determine the maximum binding signal (Deltatheta300). SPReeta results showed that Deltatheta300 was measurable for OTA concentrations down to 0.05 ppm. No significant binding of the wheat extract with MIPPy was observed when acetonitrile/water (1:1 v/v) was used as the sample loading mobile phase.; To utilize the selectivity, the MIPPy was prepared onto a stainless steel frit to make a novel muSPE device. Compared to non-imprinted polypyrrole (Ppy), MIPPy enhanced the selective binding of OTA. MIPPy-muSPE-HPLC results clearly demonstrated that the MIPPy-muSPE device afforded selective preconcentration of OTA from red wine samples, at OTA concentration levels as low as 0.05 ppb, prior to HPLC analysis. Enhancement of the total number of specific binding sites of MIPPy-on-a-frit was achieved by incorporating carbon nanotubes (CNTs) as nano fibers. The 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.; Compared with conventional preparation of MIP bulks, the electrochemical preparation of MIPPy for sensor or SPE applications is greatly simplified and attains satisfactory performance.