Dynamic headspace analysis of the release of volatile organic compounds from ethanolic systems by direct APCI-MS.

Static equilibrium headspace was diluted with a stream of nitrogen to study the stability of the volatile headspace concentration. The headspace dilution profile of 18 volatile compounds above aqueous and ethanolic solutions was measured in real time using atmospheric pressure chemical ionization-mass spectrometry. Under dynamic conditions the volatiles headspace concentration above water solutions decreased readily upon dilution. The presence of ethanol helped to maintain the volatile headspace concentration when the ethanol solution concentration was above 50 mL/L. This effect was such that under dynamic conditions the absolute volatile concentration above an ethanolic solution was higher than that above an aqueous solution, contrary to results observed in equilibrium studies. The ratio of the headspace concentration of volatiles above ethanolic 120 mL/L and water solutions was correlated to their air/water partition coefficient.