AlcoLab: Accessible Methanol Screening in Hydroalcoholic Solutions by Relative Density and Viscosity

Methanol contamination of alcoholic beverages is a persistent and frequently neglected global public health emergency. Practical detection remains largely restricted to expensive laboratory instrumentation with limited availability. This paper presents AlcoLab, a free, open-source Progressive Web Application (PWA) that performs semi-quantitative methanol screening in hydroalcoholic solutions using only a commercial 20 mL syringe, a kitchen scale (0.1 g resolution), and a smartphone. The method combines two physical properties — relative density and relative viscosity — to estimate the ternary composition (water / ethanol / methanol) of the sample. Measurements are compared against a pre-computed three-dimensional reference mesh that maps compositions as a function of density and viscosity at 20 °C. The closest composition is then tested against adjacent compositions through a Z-test for comparison of means and Monte Carlo probabilistic simulation, considering experimental uncertainty. This systematic approach ensures that all statistically plausible ternary compositions consistent with the experimental data are included in the reported results. All scientific processing occurs entirely within the user's browser via Python/Pyodide (WebAssembly), with no data transmitted to external servers. AlcoLab extends the reach of methanol screening beyond laboratories, enabling its use by health surveillance agents, health professionals, forensic investigators, distributors, and consumers. This method is intended for preliminary screening and not for confirmatory chemical analysis.