Pulse introduction membrane extraction

Juan, A.S., X. Guo, and S. Mitra. 2001. On-site and on-line analysis of chlorinated solvents in ground water using pulse introduction membrane extraction gas chromatography (PIME-GC). J. Sep. Sci. 24 599-605. 

Guo, X. and S. Mitra. 1999. Theoretical analysis of non-steady-state, pulse introduction membrane extraction with a sorbent trap interface for gas chromatographic detection. Anal. Chem. 71 4587 1593. 

Collection of analytes from a stream of gas on a sorbent bed and their release by thermal decomposition priori to the final determination stage, Membrane Extraction with Sorbent ) Interface - MESI), (Hollow Fiber Sampling Analysis -HFSA), (On-line Membrane Extraction Microtrap -OLME), (Membrane Purge and Trap - MPT), (Pulse Introduction Membrane Extraction - PIME), (Semi Permeable Membrane Devices - SPMD)... 

Guo, X. M. and Mitra, S., Development of pulse introduction membrane extraction for analysis of volatile organic compounds in individual aqueous samples, and for continuous online monitoring, J. Chromatogr. A, 826(1), 39-47, 1998. 

MESI operation requires processing of the whole sample to be extracted and has to reach steady-state permeation, which usually takes a long time. Thus, a new technical modification of MESI, called pulse introduction (flow injection-type) membrane extraction (PIME), has been developed, in which the sample is introduced to the membrane as a pulse pushed by a stream of eluent (usually water).55 This means that attaining a steady state is no longer crucial. PIME therefore provides not only a faster response and higher sensitivity, but also allows extraction of individual samples via discrete injections in addition to continuous on-line monitoring by sequential injection of a series of samples. Guo et al.56 described a mathematical model for the PIME permeation process, which showed that (a) there was a trade-off between the sensitivity and the time lag (the time taken to complete the permeation process) and (b) a large sample volume and a low flow rate enhance the sensitivity but also increase the time lag. 

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