Ethanol determination using pressure mobilization and free solution capillary electrophoresis by photo-oxidation assisted ultraviolet detection

• Capillary electrophoresis and pressure mobilization of ethanol in alkaline buffer.
• Detection by interference with in situ photo-oxidation of carbohydrates.
• Potential pathway of photo-oxidation interference investigated by NMR spectroscopy.
• Application of pressure and CE method to beverage and fermentation samples.

Free solution capillary electrophoresis (CE) can separate and quantify carbohydrates using a simple direct UV detection based on a photo-oxidation reaction taking place in the detection window without any labeling. Ethanol interferes with this photo-oxidation reaction. We thus present the first detection and quantification of ethanol using either a simple pressure mobilization set-up or CE. Ethanol can be detected down to 34.9 mg L−1 and quantified in the range 117–1850 mg L−1 through the interference with photo-oxidization of 2 g L−1 sucrose. CE can thus separate and quantify both carbohydrates and ethanol, for example to monitor a lignocellulosic fermentation process. The method is not limited to ethanol and applies to alkyl amines and other alcohols and likely to most molecules possessing the ability to react with free radicals assuming they can be sufficiently separated from each other.