The performance of a glassy carbon electrode modified with functionalized multiwalled carbon nanotubes within a poly(allylamine hydrochloride) film (GCE/PAH/MWCNTs) for the voltammetric determination of sulfite in food samples is described. The anodic peak potential for sulfite oxidation at a GCE/PAH/MWCNTs was 0.41 V whereas at GCE/PAH and GCE, the peak potentials were 0.96 and 0.89 V, respectively. Using square-wave voltammetric technique, the obtained analytical curve was linear in the sulfite concentration range from 1.1 10 À5 to 3.9 10 À4 M, with a detection limit of 4.2 mM. The electrode was successfully used to determinate sulfite in vinegar, pickle water, coconut water, and shredded coconut.

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A carbon nanotube-based sensor is proposed for the voltammetric sensing of levodopa or carbidopa in different samples.