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Low cost microstructures for preconcentration of polar and non-polar organic compounds

Silva, L.M. ; Lima, R.R. ; Carvalho, A.T. ; Silva, M.L.P. ; Mendes, J. C. ; Pereira, L.P.

Advanced Materials Vol. 514-516, Nº --, pp. 1250 - 1254, May, 2006.

ISSN (print): 0935-9648
ISSN (online): 1521-4095

Scimago Journal Ranking: 6,15 (in 2006)

Digital Object Identifier: 10.4028/

Films produced by plasma polymerization of ethyl ether and methyl or ethyl acetate show good adsorption characteristic for polar and non-polar organic compounds. These films when used in microchannels machined in a 3D-structure present some preconcentration of organic compounds. Therefore, the aim of this work is to investigate the physical-chemical preconcentration mechanisms on this structure. The test molecules used were n-hexane and 2-propanol. Quartz crystal microbalance and mass spectrometry were used to measure preconcentration. Two different procedures for reactant injection on the structure were used: a continuous flow during several minutes or a small amount injected on a single pulse and in a few seconds. The microchannels were also modified by the introduction of small ceramic particles for enhancement of the flow dispersion. It was possible to notice for all films a similar kinetic of retention. The main removal mechanism is adsorption. Although all films can provide the removal of the adsorbents molecules, the most important characteristic for the adsorption and/or retention is the surface condition. Thus, the retention of polar compound can be troubled if a non-polar compound was used previously. The most promising films for retention are ethyl ether and ethyl acetate when n-hexane and 2-propanol are used as test molecules. The results using n-hexane or 2-propanol point out the use of low-cost microchannels for preconcentration development.