Continuously operating pre-concentrators for mobile and distributed trace gas analyzers have been investigated. Micro/meso-scale trace gas concentrations increasing by a factor of 10 per stage appear to be realistic. At sampling flow rates of a few tenths of a mL/s the pumping power costs can be as low as 50 mW. Separation membranes based on quantum filtering, size filtering and diffusive mass filtering are compared. Dual function size and diffusive mass filtering membranes are the most attractive possibility. Candidate pumping systems are discussed. Concentration cascades are possible and an illustrative three stage cascade is discussed.

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