title: A critical comparison of constant and pulsed flow systems exploiting gas diffusion.
abstract: Considering the beneficial aspects arising from the implementation of pulsed flows in flow analysis, and the relevance of in-line gas diffusion as an analyte separation/concentration step, influence of flow pattern in flow systems with in-line gas diffusion was critically investigated. To this end, constant or pulsed flows delivered by syringe or solenoid pumps were exploited. For each flow pattern, two variants involving different interaction times of the donor with the acceptor streams were studied. In the first one, both the acceptor and donor streams were continuously flowing, whereas in the second one, the acceptor was stopped during the gas diffusion step. Four different volatile species (ammonia, ethanol, carbon dioxide and hydrogen sulfide) were selected as models. For the flow patterns and variants studied, the efficiencies of mass transport in the gas diffusion process were compared, and sensitivity, repeatability, sampling frequency and recorded peak shape were evaluated. Analysis of the results revealed that sensitivity is strongly dependent on the implemented variant, and that flow pattern is an important feature in flow systems with in-line gas diffusion.
authors.affiliation: Center for Nuclear Energy in Agriculture, University of Sao Paulo, 13400-970 Piracicaba, SP, Brazil; Laboratory of Environmental Analytical Chemistry, University of Balearic Islands, 07122 Palma de Mallorca, Spain.
authors.forename: Claudineia Rodrigues
authors.initials: CR
authors.lastname: Silva
authors.affiliation: Center for Nuclear Energy in Agriculture, University of Sao Paulo, 13400-970 Piracicaba, SP, Brazil; Laboratory of Environmental Analytical Chemistry, University of Balearic Islands, 07122 Palma de Mallorca, Spain.
authors.forename: Camelia
authors.initials: C
authors.lastname: Henriquez
authors.affiliation: Center for Nuclear Energy in Agriculture, University of Sao Paulo, 13400-970 Piracicaba, SP, Brazil; Laboratory of Environmental Analytical Chemistry, University of Balearic Islands, 07122 Palma de Mallorca, Spain.
authors.forename: Rejane Mara
authors.initials: RM
authors.lastname: Frizzarin
authors.affiliation: Center for Nuclear Energy in Agriculture, University of Sao Paulo, 13400-970 Piracicaba, SP, Brazil. Electronic address: ezagatto@cena.usp.br.
authors.forename: Elias Ayres Guidetti
authors.initials: EA
authors.lastname: Zagatto
authors.affiliation: Laboratory of Environmental Analytical Chemistry, University of Balearic Islands, 07122 Palma de Mallorca, Spain.
authors.forename: Victor
authors.initials: V
authors.lastname: Cerda
keywords: Constant flow; Flow analysis; Gas diffusion; Pulsed flow