New membraneless vaporization unit coupled with flow systems for analysis of ethanol

This work presents the development of a new design for a membraneless vaporization (MBL-VP) unit, called dual chamber MBL-VP for measurement of volatile compounds. With this unit, exact volumes of sample and reagent are introduced into their respective cone-shaped chambers from the base of the cones. Diffusion of volatile analyte then takes place. After an appropriate time interval, the acceptor solution is withdrawn from the chamber into the detector flow-cell, while the sample solution is withdrawn to waste. Unlike the previous MBL-VP design, problems with overflow of solutions are eliminated by precise control of the input volume to be less than the volume of the chamber. The developed flow system with the dual chamber MBL-VP unit was applied to the determination of the ethanol content of various liquid samples, using the oxidation reaction between potassium dichromate and the diffused ethanol. In addition, in order to accelerate the gas diffusion process, the donor chamber was aerated. As the result, relatively short analysis time of 144. s was achieved for ethanol content in the range of 5-50% (v/v). The proposed method was successfully validated against a gas chromatographic method for 17 alcoholic samples. Percentage recovery was in the range of 96-109%.