Preconcentration in gas or liquid phases using adsorbent thin films

Abstract

The possibility of preconcentration on microchannels for organic compounds in gas or liquid phases was evaluated. Microstructures with different geometries were mechanically machined using poly(methyl methacrylate) - PMMA as substrates and some cavities were covered with cellulose. The surfaces of the microchannels were modified by plasma deposition of hydrophilic or hydrophobic films using 2-propanol and hexamethyldisilazane (HMDS), respectively. Double layers of HMDS + 2-propanol were also used. Adsorption characterization was made by Quartz Crystal Measurements (QCM) technique using reactants in a large polarity range that showed the adsorption ability of the structures depends more on the films used than on the capillary phenomena. Cellulose modified by double layer film showed a high retention capacity for all gaseous compounds tested. However, structures without plasma deposition showed low retention capacity. Microchannels modified with double layers or 2-propanol plasma films showed higher retention than non-modified ones on gas or liquid phase

Comparison of adsorbent films obtained by plasma polymerization of oxygenated organic compounds

“…Quartz crystal measurements (QCM) were carried out [19][20][21][22][23]26] with organic compounds in a large range of polarity in order to determine adsorption characteristics of thin films, deposited on piezoelectric quartz crystal (PQC) and on microchannels. The procedures consist only in an injection of small quantities (28 mg of n-hexane and/or 0.29 mg of 2-propanol) into the system or microstructure.…”

“…Plasma deposited thin films have been used on many applications, such as surface protection and/or modification [16][17][18] and recently organic thin films were tested for adsorption of volatile organic 0925 compounds (VOCs). These films were obtained using monomers in a large range of polarity: ethyl ether, ethyl or methyl acetate, acetone, acetaldehyde and 2-propanol [19][20][21][22][23] and using 40 kHz power supply.…”

Produção de filmes compósitos a partir de tetraetilortossilicato para aplicação em estruturas miniaturizadas e em detecção de VOCs/umidade.

“…Assim, filmes porosos obtidos a partir de organo-silanos(HATTON, 2005) ou a partir de metais(BRAUNSTEIN, 2000), filmes nanoestruturados(SCHMID, 1999), ou mesmo metais depositados sobre óxido(FU, 2005) já foram testados, sendo os nanoestruturados, até o momento, os mais promissores. Outro fator a ser comentado é que muitas estruturas usadas na retenção e/ou pré-concentração requerem filmes adsorventes, e muitos destes são obtidos por polimerização por plasma.Um dos métodos muito utilizados para o desenvolvimento de estruturas miniaturizadas é a redução escalonada de estruturas macroscópicas utilizadas em plantas químicas (NASCIMENTO FILHO d , 2006;LIMA b , 2005;. SIMÕES, 2006; SILVA e , 2010).…”