Revisiting Catalytic Methods Exploiting Digital Videos: Sequential Determination of Copper and Sucrose in Sugarcane Spirits

Catalytic methods are a branch of sensitive analytical methods that demand strict time control to achieve reliable results. The present work is a pioneering exploration of digital videos recorded by a smartphone camera to accomplish catalytic methods, herein with a focus on the determination of Cu-(II) and sucrose in sugarcane spirits. In an alkaline medium (pH > 12.4), the metal ion catalyzes the air oxidation of 1,5-diphenylcarbazide (DPC, colorless) to 1,5-diphenylcarbazone (DPCO, orange) and further to 1,5-diphenylcarbadiazone (DPDO, colorless). Furthermore, the catalytic effect is inhibited due to the complexation of Cu-(II) by sucrose. Under proper adjustment of alkalinity, both analytes were determined from kinetic curves obtained by extracting the channel <i>G</i> values (RGB color system) from the videos. Under optimized conditions, linear responses were obtained from 0.06 to 0.95 mg L^-1 Cu-(II) and 0.1 to 5.0 g L^-1 sucrose (<i>r</i> ² > 0.99) with an LOD of 0.02 mg L^-1 Cu and 0.03 g L^-1 sucrose, with coefficients of variation of 4.5 and 4.2% (<i>n</i> = 10), respectively. Recoveries from 91 to 108% Cu-(II) and 95 to 118% sucrose demonstrated the absence of a matrix effect, and accuracy was assessed in relation to reference FAAS and Lane-Eynon methods. The proposed catalytic method is a cost-effective and environmentally friendly alternative for quantifying these important quality control parameters in sugarcane spirits, requiring only 60 μg of DPC and 2 mg of NaOH, with 1 mL of waste generated per determination.