Recent methanol poisoning incidents in Brazil have highlighted the urgent need for rapid, reliable, and highly sensitive methods to detect methanol contamination in alcoholic beverages. In this work, we demonstrate that the Z-scan and D4σ nonlinear optical techniques provide an exceptionally sensitive route for quantifying methanol content in water–ethanol–methanol mixtures. Using a femtosecond Ti: sapphire laser operating at 1000 nm, we measured nonlinear transmittance and beam-width variations originating from thermally induced refractive-index modulation. The thermal lens signatures of methanol and ethanol exhibit clear and quantifiable differences, enabling linear, high-precision discrimination between small changes in mixture composition. Both techniques showed excellent reproducibility, with detection sensitivity among the highest reported for optical identification of methanol contamination. These findings establish nonlinear thermal optical methods as powerful tools for real-time compositional analysis, offering a robust platform for quality control and safety assurance in the beverage industry.
Passos et al. (Fri,) studied this question.