Monitoring Microbial Activities Using Membrane Inlet Mass Spectrometry

Monitoring microbial activities in the environment is difficult owing to the lack of suitable methods. For a technique to be useful for monitoring in situ activities, it must possess the following properties: sensitivity, selectivity, stability, the ability to make continuous real-time measurements, and be noninvasive or perturbing to the microorganisms or to the environment being studied. Currently used methods include manometric techniques, microsensors, chemical assays, gas chromatography and high-performance liquid chromatography, but all have their limitations and usually require substantial disruption to the environment being studied. The principles of membrane inlet mass spectrometry (MIMS) have been described elsewhere (1 ,2 ), and are summarized in detail here. Although MIMS allows measurements of numerous gases to be made in both the liquid and gas phases, only liquid phase measurements are detailed in this example.