Using a biphasic system and digital imaging analysis with chemometric tools for simultaneous determination of Cu²⁺...

The present study reports, for the first time, the development and application of a highly efficient method based on digital imaging analysis for the simultaneous determination of Cu²⁺ and furfural in cachaça samples using a two-phase system and chemometrics tools. Furfural reacts with aniline in an acidic medium to form a Schiff base, which exhibits a pink color. On the other hand, Cu²⁺ reacts with cuprizone in a basic medium to form a blue complex. The two reactions were performed on a porcelain plate, and a smartphone was used to capture the colorimetric images. Partial least squares (PLS) regression was used to construct the prediction models for Cu²⁺ and furfural contents in cachaça samples. After finding the best PLS models, the ordered predictor selection (OPS) analysis was performed in order to select the most predictive variables. The method developed was found to be effective in estimating the amounts of Cu²⁺ and furfural in cachaça samples, with a mean absolute error of 0.2 mg L^-1 for the Cu²⁺ model, and 0.3 mg per 100 mL of anhydrous alcohol for the furfural model. The method proposed in this study is simple and straightforward; it does not require complex technical knowledge and can be used by the producers themselves in the cachaça manufacturing process.