Preparation and characterisation of polypyrrole - carbon nanomaterial composite solid-phase microextraction fibres and their applications to the determination of fungicide residues in grape juice samples

Present study describes the use of a lab-made polypyrrole (PPy) coated solid phase microextraction (SPME) fibres modified with carbonaceous nanomaterials for effective adsorption of volatile fungicides used in vineyards for subsequent determination by gas chromatography coupled with a mass spectrometer. The SPME fibres were fabricated electrochemically by dipping a stainless steel wire in a cell containing pyrrole monomer where the polymeric film was coated on the wire by cycling the potential between -0.5 and 2.0 V at a rate of 50 mV s(-1). Then, the procedure was repeated in the presence of multi-walled carbon nanotubes (MWCNTs) or graphene (Gr) nanoplates dispersed in tartrate solution. The coated fibres were attached to a holder for subsequent headspace extraction of volatile fungicides in grape juice samples. Initial studies were conducted with commercial fibres adoptable to a fully automated system and optimal conditions were studied by using an 85 mu m PA fibre. Then, the fabricated fibres have been tested manually under optimised conditions for unbiased comparison. Overall results have suggested that PPy-MWCNT-SPME and PPy-Gr-SPME have given the comparable results with commercial fibres in the concentration range of 1.0-50 ng mL(-1) by allowing the determination of these fungicides at LOQ levels varied in the range of 0.55-6.94 ng mL(-1) ranges. In comparison to the literature values, more results that are sensitive were obtained with these two fibres with satisfactory recovery values without any solvent consumption or labour-intensive pre-treatment processes.