title: A novel flow-based procedure for automation of respirometric assays in soils.
abstract: A flow-based strategy involving a gas-diffusion sampling probe was proposed for evaluating the respiration rate in soils. The amount of CO2 collected after a pre-defined time interval was proportional to the free CO2 released by the soil ecosystem. The 500-mL incubation flasks typically used for soil respirometric assays were adapted and a special cover was designed for connecting a tubular gas diffusion membrane, a fan, and a septum for adding the CO2(g) standards required for calibration. The method relied on the pH-dependent absorbance variations resulting from the CO2 collection. A 1.3mmolL(-1) bromothymol blue solution (pH 7.0) acted as both acceptor and carrier streams. In order to widen the dynamical working range to 0.003-0.2mmol CO2, two analytical curves were obtained, each related to a different time interval for the CO2 collection. Kinetic curves related to CO2 release by the soil samples were straightforwardly attained. Repeatability and detection limit were estimated as 2.0% and 0.001mmol CO2 (n=10), and accuracy was assessed in relation to a recommended titrimetric procedure.
authors.affiliation: Centre for Nuclear Energy in Agriculture, University of Sao Paulo, Piracicaba, SP, Brazil.
authors.forename: Claudineia R
authors.initials: CR
authors.lastname: Silva
authors.affiliation: Centre for Nuclear Energy in Agriculture, University of Sao Paulo, Piracicaba, SP, Brazil.
authors.forename: Eliezer
authors.initials: E
authors.lastname: Oliveira
authors.affiliation: Centre for Nuclear Energy in Agriculture, University of Sao Paulo, Piracicaba, SP, Brazil.
authors.forename: Elias A G
authors.initials: EAG
authors.lastname: Zagatto
authors.affiliation: Centre for Nuclear Energy in Agriculture, University of Sao Paulo, Piracicaba, SP, Brazil. Electronic address: cameliahenriquez@gmail.com.
authors.forename: Camelia
authors.initials: C
authors.lastname: Henriquez
mesh_terms: D001331:Automation; D002245:Carbon Dioxide / Q000032:analysis*; D004058:Diffusion; D012987:Soil / Q000737:chemistry; D012988:Soil Microbiology
chemical_list: D012987:Soil; D002245:Carbon Dioxide
keywords: Flow analysis; Gas diffusion; Respirometric assays; Sampling probe; Soils