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 µm 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.