Electrodeposition of 4-Benzenesulfonic Acid onto a Graphite-Epoxy Composite Electrode for the Enhanced Voltammetric Determination of Caffeine in Beverages

Figure 7

Voltammograms obtained for one of the sample measurements. From bottom to top, it shows a blank measurement (20.0 mL of a 0.04 mol·L⁻¹ BRB pH 2 solution), followed by an addition of 0.5 mL of the sample, and four caffeine spikes of 0.1 mL from a standard of 5 × 10⁻³ mol·L⁻¹. SWV parameters: frequency of 12 Hz, pulse amplitude of 100 mV, and potential step of 10 mV. Standard addition curve: i = 0.1156 + 4.74 × 10⁻⁷; r² = 0.998.