| Summary: | A sensitive procedure was developed for the simultaneous determination of ascorbic acid (AA), dopamine (DA), uric acid (UA) and tryptophan (TRP) using a composite electrode based on carbon black nanoballs (CBNB) and carbon nanotubes (CNTs). The CBNB/CNTs/GCE presented well-defined voltammetric peaks for AA, DA, UA and TRP. The proposed procedure has also exhibited excellent catalytic activities and achieved large enhancements of the current responses of DA, AA, UA and TRP. Simultaneous determination at CBNB/CNTs/GCE was carried out by means of square wave voltammetry (SWV). Anodic current responses changed linearly with the concentrations in the range of 2.0 × 10−5–4.0 × 10−4 M for AA, 5.0 × 10−8–2.75 × 10−6 M for DA, 1.0 × 10−6–4.5 × 10−5 M for UA and 2.5 × 10−8–4.8 × 10−6 M for TRP. Detection limits obtained at CBNB/CNTs/GCE were 5.71 × 10−6 M for AA, 1.7 × 10−8 M for DA, 4.2 × 10−7 M for UA and 1.1 × 10−8 M for TRP. The composite of CNTs and CBNB provided good reproducibility and excellent selectivity for DA, AA, UA and TRP. The proposed procedure has also applied to pharmaceuticals and food samples with satisfactory results. Keywords: Carbon black nanoballs, Carbon nanotubes, Electroanalysis, Selectivity, Sensor
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