On-line flow injection analysis of volatile organic compounds in seawater by membrane introduction mass spectrometry.

The combination of flow injection analysis with membrane introduction mass spectrometry for analysis of volatile organic compounds (VOCs) in seawater is examined and is compared to measurements made in water. Membrane introduction mass spectrometry is performed using a benchtop ion trap mass spectrometer, and characterization of various aspects of the flow injection and ion trap combination for the analysis of volatile organic compounds (including anthropogenic halocarbons) in seawater is carried out. The analyte responses are shown to be linear over several orders of magnitude (e.g. for methylene chloride), independent of seawater pH (e.g. for chlorobenzene) and independent of matrix effects for the VOCs studied. A comparison of the performance of a microporous (Teflon) membrane with that of an amorphous silicone membrane is made, and the former is shown to provide lower detection limits which are in the parts-per-trillion range (300 ppt for chlorobenzene, 190 ppt for trans-1,2-dichloroethene). The microporous membrane provides faster response times by a factor of four to five for relatively more polar compounds, such as chlorobenzene. An analysis of a seven-component mixture demonstrates the ability of this on-line combination to allow multicomponent analysis of mixtures of some complexity.