ONLINE 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. M embrane introduction mass spectrometry is performed using a benchtop i on trap mass spectrometer, and characterization of various aspects of the flow injection and ion trap combination for the analysis of volati le organic compounds (including anthropogenic halocarbons) in seawater is carried out. The analyte responses are shown to be linear over sev eral orders of magnitude (e.g. for methylene chloride), independent of seawater pH (e.g. for chlorobenzene) and independent of matrix effect s for the VOCs studied. A comparison of the performance of a microporo us (Teflon) membrane with that of an amorphous silicone membrane is ma de, and the former is shown to provide lower detection limits which ar e in the parts-per-trillion range (300 ppt for chlorobenzene, 190 ppt for trans-1,2-dichloroethene). The microporous membrane provides faste r response times by a factor of four to five for relatively more polar compounds, such as chlorobenzene. An analysis of a seven-component mi xture demonstrates the ability of this on-line combination to allow mu lticomponent analysis of mixtures of some complexity.