title: A highly reproducible solenoid micropump system for the analysis of total inorganic carbon and ammonium using gas-diffusion with conductimetric detection.
abstract: In this work, a simple, economic, and miniaturized flow-based analyzer based on solenoid micropumps is presented. It was applied to determine two parameters of high environmental interest: ammonium and total inorganic carbon (TIC) in natural waters. The method is based on gas diffusion (GD) of CO₂ and NH3 through a hydrophobic gas permeable membrane from an acidic or alkaline donor stream, respectively. The analytes are trapped in an acceptor solution, being slightly alkaline for CO₂ and slightly acidic for NH₃. The analytes are quantified using a homemade stainless steel conductimetric cell. The proposed system required five solenoid micro-pumps, one for each reagent and sample. Two especially made air bubble traps were placed down-stream of the solendoid pumps, which provided the acceptor solutions, by this increasing the method's reproducibility. Values of RSD lower than 1% were obtained. Achieved limits of detection were 0.27 µmol L⁻¹ for NH₄⁺ and 50 µmol L⁻¹ for TIC. Add-recovery tests were used to prove the trueness of the method and recoveries of 99.5 ± 7.5% were obtained for both analytes. The proposed system proved to be adequate for monitoring purpose of TIC and NH₄⁺ due to its high sample throughput and repeatability.
authors.affiliation: Laboratory of Environmental Analytical Chemistry, University of Balearic Island, CP: 07122 Palma de Mallorca, Spain. Electronic address: cameliahenriquez@gmail.com.
authors.forename: Camelia
authors.initials: C
authors.lastname: Henríquez
authors.forename: Burkhard
authors.initials: B
authors.lastname: Horstkotte
authors.forename: Víctor
authors.initials: V
authors.lastname: Cerdà
mesh_terms: D064751:Ammonium Compounds / Q000032:analysis*; D002245:Carbon Dioxide / Q000032:analysis*; D004058:Diffusion; D004553:Electric Conductivity; D017022:Flow Injection Analysis / Q000379:methods*; D005740:Gases / Q000737:chemistry*; D055616:Microtechnology / Q000295:instrumentation*
chemical_list: D064751:Ammonium Compounds; D005740:Gases; D002245:Carbon Dioxide
keywords: Ammonium; Conductimetric detection; Gas difussion; Multipumping flow system; Solenoid micropumps; Total inorganic carbon