Chromatographic Sample Collection from Two Phase (gas + liquid) Flows
Thomas J. Bruno, Bret Windom
A particularly challenging sample presentation in analytical chemistry is a flowing stream that consists of both a gas and liquid phase, in the situation in which an analysis is needed for both phases, separately. In these cases, the vapor and liquid must be physically separated before the individual phases can be collected and analyzed; it is not possible to analyze two phase flows otherwise. Though the two phases are at equilibrium, it is imperative that no liquid contaminate the vapor, and no vapor be entrained in the liquid at a given temperature and pressure. In this paper, we describe a simple device that can individually separate and collect the vapor and liquid phases of a two phase flow. The apparatus, called P2SC, uses an adaptation of the branch point separator used in natural gas transmissions lines, with vapor collection done downstream in a metal bellows. The liquid collection is done in a length of Teflon tube. The separated vapor and liquid phases are then easily transferred into any desired analytical instrument with a syringe, although any sample introduction method, such as a valve, could be used as well. We discuss the application of this device with a stream of thermally stressed rocket kerosene.