Membrane extraction sorbent interface

After this isolation step, analytes are usually concentrated in sorbent traps (membrane extraction sorbent interface [MESI]) and thermally desorbed in a cryofocusing device or directly in a gas chromatographic column. In other cases,no sorbent trap is used, analytes are desorbed directly from the membrane unit cell (thermal membrane desorption [TMD]) and carried by a gas stream onto the front of the chromatographic column of the analytical system. 

Classical LLEs have also been replaced by membrane extractions such as SLM (supported liquid membrane extraction), MMLLE (microporous membrane liquid-liquid extraction) and MESI (membrane extraction with a sorbent interface). All of these techniques use a nonporous membrane, involving partitioning of the analytes [499]. SLM is a sample handling technique which can be used for selective extraction of a particular class of compounds from complex (aqueous) matrices [500]. Membrane extraction with a sorbent interface (MESI) is suitable for VOC analysis (e.g. in a MESI- xGC-TCD configuration) [501,502]. 

MESI Membrane extraction with sorbent interface... 

The use of silicone membranes as an interface in MIMS for direct extraction and analysis by MS has fostered their implementation for extraction purposes that can be combined off-line or on-line with other analytical instrumentation, such as GC. The technique of membrane extraction with sorbent interface (MESI) (Figure 4.2) employs the pervaporation principle in a nonporous polymeric membrane unit, where the membrane is used as a selective barrier for the extraction of VOCs and SVOCs in gaseous or liquid samples. 

Luo, Y.Z. and J. Pawliszyn. 2000. Membrane extraction with a sorbent interface for headspace monitoring of aqueous samples using a cap sampling device. Anal. Chem. 72 1058-1063. 

Segal, A., T. Gorecki, P. Mussche, J. Lips, and J. Pawliszyn. 2000. Development of membrane extraction with a sorbent interface-micro gas chromatography system for field analysis. J. Chromatogr. A 873 13-27. 

Liu, X. and J. Pawliszyn. 2005. On-site environmental analysis by membrane extraction with a sorbent interface combined with a portable gas chromatograph system. Int. J. Environ. Anal. Chem. 85 1189-1200. 

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. 

Membrane SLM MESI MMLLE MIMS PME HF-LPME MASE LGLME Headspace-solid phase dynamic extraction (HS-SPDE) Purge-and-membrane extraction Headspace/membrane extraction w. sorbent interface (HS-MESI) Headspace/membrane inlet mass spectrometry (HS-MIMS)... 

In an attempt to overcome the significant difficulties that the presence of water vapor poses to the analysis of very volatile compounds, purge-and-membrane extraction techniques have been developed that largely prevent the introduction of water into the analytical system. Typical implementations of this form of sample introduction have been called by its developers membrane extraction with a sorbent interface (MESI),97 or membrane introduction mass spectrometry (MIMS).98 " They are based on a silicone hollow-fiber membrane that is inserted into the sample to be monitored, and the passing of a certain volume of inert gas through the membrane. Volatile compounds permeate the membrane and are swept to the adsorbent trap from which they are desorbed into the GC. This method of sample introduction is particularly suited for field and process monitoring and for dirty samples, since it prevents any nonvolatile compounds from entering the analytical system.100... 

Membrane extraction with a sorbent interface (MESI). 

MESI Membrane extraction with a sorbent interface Nonporous Gaseous/polymer/gaseous Liquid/polymer/gaseous... 

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)... 

Y. Luo and J. Pawliszyn, Solid phase microextraction (SPME) and membrane extraction with a sorbent interface (MESI) in organic analysis, in A. J. Handley, ed., Extraction Methods in Organic Analysis, Sheffield Academic Press, Sheffield, Yorkshire, England, 1999, pp. 75-99. 

Membrane extraction with sorbent interface (MESI) is an interesting example of an extraction device, which is the most useful system for interfacing with GC. In this approach, the donor phase is a gas or a liquid sample, and the acceptor phase is a gas. The volatiles are continuously trapped on sorbent and then desorbed into GC [112]. Another solution is a combination of off-line GC-MESI through a cryogenic trap, which allows preparation of environmental samples in the field and performance of GC analysis after transportation to the laboratory [113,114]. MESI allows the extraction of volatile and relatively nonpolar analytes. 

Matz, G., Kibelka, G., Dahl, J., Leimeman, F. Experimental study on solvent-less sample preparation methods - membrane extraction with a sorbent interface, thermal membrane desorption application and purge-and-trap. J. Chromatogr. 830, 365-376 (1999)... 

Note SLM, supported liquid membrane (aq/org/aq) MMLLE, microporous membrane liquid-liquid extraction (aq/org) PME, polymer membrane extraction (aq/polymer/org) MESI, membrane extraction with sorbent interface (aq (or gas)/polymer/gas/sorbent) CFLME, continuous flow liquid membrane extraction (aq/org (in flow)/aq) LPME2, two-phase liquid phase microextraction in hoUow fibers (aq/org) LPME3, three-phase liquid phase microextraction in hollow fibers (aq/org/aq). 

There are different variations of the MASX technique, including supported liquid membrane extraction (SLM), microporous membrane liquid-liquid extraction (MMLLE), polymeric membrane extraction (PME) and membrane extraction with a sorbent interface (MESI). These techniques will be briefly described below. 

Luo, Y. Z., Adams, M., and Pawliszyn, J., Aqueous sample direct extraction and analysis by membrane extraction with a sorbent interface. Analyst, 122(12), 1461-1469, 1997. 

Lord, H. Yn, Y.R Segal, A. Pawliszyn, J., Breath analysis and monitoring by membrane extraction with sorbent interface. Anal. Chem. 2002, 74,5650-5657. 

The techniques mentioned earlier are all characterized by liquid donor and acceptor phases. However, a gaseous acceptor phase is also possible, and that would be the most convenient and compatible arrangement for direct connection with GC. This is realized with the membrane extraction with a sorbent interface (MESI) technique. MESI can be used for either gaseous or aqueous samples, and the equipment employs a membrane module with a (usually) silicone rubber hollow fiber, into which the analytes are extracted from the surrounding liquid or gaseous sample. The carrier gas of a gas chromatograph flows inside the fiber and transports the analyte molecules as they are extracted from the membrane into a cooled sorbent trap where they are trapped. The analytes are subsequently desorbed from the sorbent trap by heating and are transferred to GC analysis. 

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