Polypyrrole-coated carbon fibre electrodes for paracetamol and clozapine drug sensing
Sutthima Sriprasertsuk, Simone Mathias, John R. Varcoe, Carol Crean
Abstract
Polypyrrole (PPy) fibre electrodes were studied to determine their ability to sense paracetamol (as a model drug) in the presence of the interferents dopamine and ascorbic acid. PPy was electropolymerised onto carbon fibres using cyclic voltammetry in the presence of two different counter anions: sodium dodecyl sulfate (SDS) and potassium nitrate (KNO3). The surface of the PPy.SDS and PPy.KNO3 fibre electrodes was characterised using Raman spectroscopy and scanning electron microscopy. The PPy.SDS-coated carbon fibre had a 14-fold larger electrochemical surface area compared to a bare carbon fibre (calculated using the Randles-Sevcik equation). The use of a large counter anion as dopant (dodecyl sulfate) produced fibres with a greater drug sensing response (cf. the use of smaller nitrate anion). The use of the PPy.SDS fibre electrode in differential pulse voltammetry (DPV) allowed sensing of paracetamol with a detection limit (3σ S/N) of 34 µM. For the anodic peak current (0.5 V vs. Ag/AgCl), a linear response range was observed for 50–500 µM. At a paracetamol concentration of 100 µM, the DPV anodic peak current (at 0.5 V vs. Ag/AgCl) was unaffected by the addition of interferents: 100 µM dopamine and 100 µM ascorbic acid. A real-world application of drug sensing was trialled with the anti-psychotic medication clozapine; where the PPy.SDS carbon fibre could sense clozapine with a detection limit of (3σ S/N) of 6 µM and a sensitivity of 15 μA cm−2 μmol−1 L.