Development and optimization of a membrane-inlet-photoionization mass spectrometer for real-time analysis of (poly)aromatic and halogenated compounds in aquatic systems

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Fast and sensitive analysis of (poly)aromatic and halogenated compounds is of high importance due to their environmental behavior, high biological activity and toxicity. Very low concentrations of such compounds in marine environments make their detection and monitoring difficult. Therefore, currently laborious enrichment techniques (such as purge-and-trap and extraction) are applied. A promising alternative in this regard is resonance-enhanced multiphoton ionization (REMPI) coupled to time-of-flight mass spectrometry. As a result of the specific ionization scheme REMPI provides selective and sensitive detection of (poly)aromatic species. A challenge for the utilization of REMPI in aquatic systems is the transfer of dissolved analytes to the gas phase. An auspicious approach constitutes the application of membrane inlets. For membrane inlet mass spectrometry (MIMS) analytes are transported selectively from the liquid phase through a semipermeable membrane into the vacuum of the mass spectrometer, losing the matrix in the process. Advantages are enrichment of the analytes on the membrane surface and a considerable reduction of analysis time. In the framework of the proposed project a REMPI-MIMS system for real-time analysis of (poly)aromatic and halogenated compounds in sea water will be developed and optimized for employment on a research ship cruise in the Baltic Sea. Besides planning and construction of a membrane inlet the development and characterization of a robust coupling of the inlet to a mass spectrometer is put forward. By doing this, improvement of limits of detection takes center stage. Furthermore several parameters such as temperature and salinity will be investigated with respect to the performance of the new analytical system. Validation of the system will be cross-checked by GC-MS measurements.