A reagentless flow injection system for the quantification of ethanol in beverages based on the schlieren effect measurement

• Simple and reagentless flow-injection system based on the schlieren effect measurement
• The analyte is separated from the sample matrix prior to analysis by means of a gas-diffusion unit.
• The intrinsic absorption of the sample matrix is eliminated by means of the membrane-based separation technique.
• Successful application to red and white table wine, port wine, beers, liquors, spirits and brandies

A flow injection system comprising a gas-diffusion unit and schlieren effect detection was arranged in order to develop a simple methodology for the quantification of ethanol in different alcoholic beverages. It was possible to establish a linear range up to 25% (v/v), with a LOD and a LOQ of 0.6% and 2.0% (v/v), respectively; with good repeatability, RSD < 4.6%. Only 80 μL of sample was needed for quantification with a determination rate of one determination per minute.To evaluate the accuracy of the proposed method, a total of 43 alcoholic beverages, red and white table wine, port wine, beers, liquors, spirits and brandies were analysed. The results obtained by the developed method were in good agreement with the ones obtained by the reference method.