Electrochemical sensor based on ionic liquid and carbon black for voltammetric determination of Allura red colorant at nanomolar levels in soft drink powders

The ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate and carbon black (CB) nanoparticles were incorporated within a crosslinked chitosan film over the surface of a glassy carbon electrode, and the obtained architecture explored to the sensitive voltammetric sensing of Allure red colorant in soft drinking powders. The different electrodic surfaces were morphologically and electrochemically characterized. From the modification of glassy carbon electrode with IL and CB, a significantly enhanced voltammetric response was achieved toward the Allura red irreversible oxidation reaction. The type and amount of IL employed in the electrode modification step as well as all the others experimental parameters affecting the sensor response by square-wave adsorptive anodic stripping voltammetry (SWAdASV) were systematically optimized. Under the optimum experimental conditions, the proposed SWAdASV procedure provided a linear analytical curve in the concentration range of 3.98 x 10(-8) to 9.09 x 10(-7) mol L-1 and a low limit of detection of 9,1 x 10(-10) mol L-1 (0.91 nmol L-1). The proposed sensor presented good precision and no matrice effects as shown from repeatability tests, concomitant studies and addition/recovery assays. The developed SWAdASV procedure was applied successfully in the determination of Allura red content in commercial soft drink powder samples, and the results were in close agreement with those obtained using a comparative spectrophotometric method at a confidence level of 95%.