title: Development and application of a microfluidic in-situ analyzer for dissolved Fe and Mn in natural waters.
abstract: The redox sensitive trace metals iron and manganese are two important elements that help shape the biogeochemistry of aquatic systems and thus their measurement is important. Current laboratory methods are expensive, time consuming and cannot provide the spatial and temporal resolution needed to characterize these elements in natural waters. Here we describe the first autonomous analyzer capable of providing vertical profiles as well as routine in-situ determinations of dissolved Fe(II) and Mn in aquatic environments. The spectrophotometric sensor uses microfluidic methods (Lab-on-a-chip technology) and mixes reagents and samples using a novel in-cell diffusion process. Fe(II) and Mn can be measured with a frequency of up to 12 and 6 samples per hour respectively with limits of detection of 27nM for Fe(II), 2.1% precision (n=20), and 28nM for Mn, 2.4% precision (n=19). The device combines relatively low cost, low power usage, low reagent consumption, portability, and tolerance to pressures up to at least 170 bars, with high precision and accuracy. We present data from a successful demonstration of the sensor during a cruise to the Gotland and Landsort Deep Basins of the Baltic Sea.
authors.affiliation: National Oceanography Centre, University of Southampton Waterfront Campus, Southampton SO14 3ZH, United Kingdom; Ocean and Earth Science, University of Southampton Waterfront Campus, Southampton SO14 3ZH, United Kingdom. Electronic address: ambra.milani@gmail.com.
authors.forename: Ambra
authors.initials: A
authors.lastname: Milani
authors.affiliation: Ocean and Earth Science, University of Southampton Waterfront Campus, Southampton SO14 3ZH, United Kingdom.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Statham
authors.affiliation: National Oceanography Centre, University of Southampton Waterfront Campus, Southampton SO14 3ZH, United Kingdom.
authors.forename: Matt C
authors.initials: MC
authors.lastname: Mowlem
authors.affiliation: National Oceanography Centre, University of Southampton Waterfront Campus, Southampton SO14 3ZH, United Kingdom.
authors.forename: Douglas P
authors.initials: DP
authors.lastname: Connelly
mesh_terms: D007501:Iron / Q000032:analysis*; D008345:Manganese / Q000032:analysis*; D044085:Microfluidics; D009792:Oceans and Seas; D012623:Seawater / Q000032:analysis*
chemical_list: D008345:Manganese; D007501:Iron
keywords: In-situ sensor; Iron; Lab-on-a-chip; Manganese; Trace metal analysis