Molecularly Imprinted Solid Phase Extraction in a Syringe Needle Packed with Polypyrrole-encapsulated Carbon Nanotubes for Determination of Ochratoxin A in Red Wine

A novel micro-solid phase preconcentration (μSPP) device is developed by electrochemically depositing molecularly imprinted polypyrrole (MIPPy) over carbon nanotubes (CNTs) packed inside a 22-gauge syringe needle. The ochratoxin A (OTA) template is removed with 1% triethylamine (TEA) in 20:80 v/v acetonitrile--ammonia buffer (20 mM NH₄Cl/NH₃, pH 9.2). This syringe needle is used to extract trace OTA in a red wine sample, and the preconcentrated OTA is eluted with 1% (v/v) TEA in 20:80 v/v acetonitrile--ammonia buffer (20 mM NH₄Cl/NH₃, pH 9.2). The eluate is analyzed by high performance liquid chromatography (HPLC) with fluorescence detection (FD). The results demonstrated a significantly selective enrichment of OTA at sub-ppb levels in the presence of red wine matrix components. Using a sample volume of 0.5mL red wine for preconcentration, it is possible to determine OTA down to a detection limit of 0.04 ng/mL (at 3σB) or a quantification limit of 0.10 ng/mL (at 10σB). The total MIPPy/CNTs-μSPP-HPLC-FD analysis took only 40min, including a μSPP time of 30min, elution time of 20 s, and HPLC analysis time of 10 min. This needle can be reused and hence readily adapted in an autosampler for the processing of multiple samples in series.