Voltammetric detection of caffeine in pharmacological and beverages samples based on simple nano- Co (II, III) oxide modified carbon paste electrode in aqueous and micellar media

Caffeine (Caf) is one of the most widespread compounds in food components, beverages and medicines, which drives us to find a simple, fast and convenient method for its determination. The promising Nano-Cobalt (II, III) oxide modified carbon paste (NCOMCP) sensor was fabricated and applied to the sensitive determination of Caf in both aqueous (0.01 mol L−1 H2SO4) and micellar media (0.5 mmol L−1 sodium dodecylsulfate, SDS). Surface characterization was performed utilizing scanning electron microscopy (SEM) and energy dispersive analysis of X-rays (EDX). The electrochemical behavior of Caf was studied by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA). From these experiments, the apparent diffusion coefficient (Dapp) and catalytic rate constant (kcat) were evaluated to be 4.2 × 10-5 cm2 s-1 and 1.92 × 103 mol−1 L-2 s-1, respectively. Caf can be detected in a concentration range between 5.0 and 600 μmol L−1, with a limit of detection (LOD) of 0.016 μmol L−1, as determined from the calibration plot obtained using differential pulse voltammetry (DPV). The sensor was applicable for Caf sensing in several commercial real samples with recoveries ranging from 98.9% to 101.9%. It exhibited good selectivity in the presence of common interferences.