Amperometric determination of ascorbic acid using multiwalled carbon nanotube-thiolated polyaniline composite modified glassy carbon electrode

A new nanocomposite film that is highly electroactive in neutral aqueous solutions was prepared based on multiwalled carbon nanotubes (MWCNTs), polyaniline (PANI) and mercaptosuccinic acid (MSA). Briefly, a glassy carbon electrode (GCE) was firstly cast-coated with MWCNTs (MWCNTs/GCE), PANI was then electrodeposited on MWCNTs/GCE, and finally MSA was tethered to the electrooxidized PANI via the thiol-ene reaction to form MSA–PANI/MWCNTs/GCE. Electrochemical quartz crystal microbalance, scanning electron microscopy, Fourier transform infrared spectroscopy and electrochemical impedance spectroscopy were used for film characterization and process monitoring. The high electroactivity of MSA–PANI/MWCNTs/GCE observed in neutral aqueous solutions is ascribed to the anionic MSA tethered to the PANI backbones as well as the good conductivity and high specific surface area of MWCNTs. The prepared MSA–PANI/MWCNTs/GCE electrode was successfully used for catalytic electroanalysis of ascorbic acid (AA) at neutral pH. Under optimum conditions, the anodic amperometric detection of AA provides a wide linear detection range (20 μM–29.6 mM), a high sensitivity (363 μA mM−1 cm−2) and a low limit of detection (0.6 μM, S/N = 3) as well as good reproducibility and stability, which are superior to many reported AA electrochemical sensors.