Determination of Ethanol in Gel Hand Sanitizers Using Mid and Near Infrared Spectroscopy

Alcohol-based gel hand sanitizers became very popular during the COVID-19 (coronavirus disease 2019) pandemic. In Brazil, several irregular factories emerged requiring an efficient control by the police and regulatory agencies to guarantee product quality. This problem required a method to determine ethanol content, which led to the development of two methods employing mid and near infrared spectroscopy associated with chemometrics. Partial least squares (PLS) models were built and presented satisfactory results with mean absolute percentage error of prediction and root mean square error of prediction (RMSEP) of 1.12 and 0.76% (m/m), respectively, for mid-infrared (MIR) and 1.83 and 1.18% (m/m) for near-infrared (NIR). The analysis of commercial and seized samples of hand sanitizers showed that only 7 out of 34 samples had an ethanol content of 70% (m/m) or higher. This result reinforces the need for constant vigilance by authorities to ensure that the products have the required specifications.