A novel flow-based procedure for automation of respirometric assays in soils

• Published in: Talanta (Oxford) 2016-09, Vol.158, p.14-20
• Main Authors: Silva, Claudineia R., Oliveira, Eliezer, Zagatto, Elias A.G., Henriquez, Camelia
• Format: Article
• Language: English
• Subjects: Assaying; Automation; Carbon dioxide; Carbon Dioxide - analysis; Collection; Diffusion; Flow analysis; Gas diffusion; Intervals; Respirometric assays; Sampling; Sampling probe; Soil - chemistry; Soil Microbiology; Soils
• ISSN: 0039-9140; 1873-3573
• DOI: 10.1016/j.talanta.2016.05.026

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. [Display omitted] •Gas diffusion tubular membrane as a probe for respirometric assay automation.•Several accumulation times for widen the concentration dynamical range.•Simple, rugged and low-cost analytical flow system.•Strategy readily applicable to routine respirometric assays.•Simultaneous sample handling for investigating the kinetics of CO2 release.