Elimination of matrix effects for static headspace analysis of ethanol.

The intention of this work was to develop a simple and fast procedure for a determination of small amounts of ethanol in aqueous protein containing solutions based on combined headspace gas chromatography. In order to provide for short analysis time static headspace methodology was considered for this purpose. In this context the influence of the matrix composition onto the analytical results has been established and internal standardization as well as a full evaporation technique have been evaluated as promising alternatives for a compensation of matrix effects. With respect to speed of analysis, simplicity of sample handling as well as the quality of the analytical performance parameters, precision and accuracy, the full evaporation technique proved to be superior. Thus, the static equilibration of a 20 microliters sample aliquot in a conventional headspace sample vial for 5 min at 100 degrees C is sufficient to obtain equilibrium conditions for gas chromatographic analysis. The accuracy of this method was verified by robust regression analysis and exhibited excellent robustness within the required limits of sample composition ranging from 0 to 20% (w/w) protein content and up to 5 g/l salt content.