Smartphone-based digital imaging for rapid and green quantification of aspartame in lemon-flavored soft drinks

Smartphone-based digital images methods (DIA-PH and DIA-CG) were developed to quantify aspartame in lemon-flavored soft drinks, motivated by classification of aspartame as a possible carcinogen by the International Agency for Research on Cancer. A colorimetric reaction was optimized to replace toxic solvents with water for the formation of Ruhemann's purple, and UV-Vis spectrophotometry, DIA-PH, and DIA-CG analysis were performed. The validation involved linear analytical curves (R² > 0.99) in concentration range of 0.005-0.200 mg mL^-1, as well as homoscedasticity, and normally distributed residuals, using the green channel (G) for DIA methods. DIA-PH exhibited superior sensitivity (LOD/LOQ: 2.0 × 10^-4 / 6.0 × 10^-4 mg mL^-1), indicating its suitability for regulatory monitoring. Aspartame in commercial samples was below the limits by ANVISA-Brazilian (0.75 mg mL^-1) and European Union (1.0 mg mL^-1) legislations. The methods have proven to be low-cost, aligned with green chemistry, and suitable for quality control of aspartame in soft drinks.