Low Cost Microstructures for Preconcentration of Polar and Non-Polar Organic Compounds
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.
Paula Maria Vilarinho
L. M. Silva, R. R. Lima, A. T. Carvalho, M. L. P. Silva, J. C. Madaleno, L. Pereira, "Low Cost Microstructures for Preconcentration of Polar and Non-Polar Organic Compounds", Materials Science Forum, Vols. 514-516, pp. 1250-1254, 2006