A Lab-on-Chip Analyzer for in Situ Measurement of Soluble Reactive Phosphate: Improved Phosphate Blue Assay and Application to Fluvial Monitoring

Abstract

Here, we present a new in situ microfluidic phosphate sensor that features an improved "phosphate blue" assay which includes polyvinylpyrrolidone in place of traditional surfactants-improving sensitivity and reducing temperature effects. The sensor features greater power economy and analytical performance relative to commercially available alternatives, with a mean power consumption of 1.8 W, a detection limit of 40 nM, a dynamic range of 0.14-10 μM, and an infield accuracy of 4 ± 4.5%. During field testing, the sensor was continuously deployed for 9 weeks in a chalk stream, revealing complex relations between flow rates and phosphate concentration that suggest changing dominance in phosphate sources. A distinct diel phosphorus signal was observed under low flow conditions, highlighting the ability of the sensor to decouple geochemical and biotic effects on phosphate dynamics in fluvial environments. This paper highlights the importance of high resolution in situ sensors in addressing the current gross under-sampling of aquatic environments.

A Lab-On-Chip Phosphate Analyzer for Long-term In Situ Monitoring at Fixed Observatories: Optimization and Performance Evaluation in Estuarine and Oligotrophic Coastal Waters

“…The molybdophosphoric acid is then reduced to phosphomolybdenum blue using ascorbic acid and its absorbance is quantified at 700 nm. The molybdenum blue assay implemented in this work has been optimized for in situ work using microfluidics (Clinton-Bailey et al, 2017).…”

Emerging Trends in Microfluidics Based Devices

“…FDS have the advantages of being capable of being used in‐situ and continuously function for a long duration of time without any external assistance. [ 103 ] Nightingale et al. fabricated a pen‐sized system utilizing a MFs chip operating on the standard Griess method for continuous analysis of nitrates and nitrites in river water.…”

Toward a Harmonization for Using in situ Nutrient Sensors in the Marine Environment

“…However, wet chemical analyzers may not always be suitable for long-term deployment due to limited lifetime of reagents and standards and waste disposal concerns. Most wet chemical sensors have been deployed on platforms for the collection of high-frequency timeseries of surface coastal waters at a fixed station (NAS3X, Mills et al, 2005;CHEMINI, Répécaud et al, 2009;WIZ, Vuillemin et al, 2009b;LoC, Beaton et al, 2017;Clinton-Bailey et al, 2017;Grand et al, 2017). FerryBox-systems (Petersen et al, 2011) also provide a compatible observing infrastructure for wet chemical analyzers to collect surface nutrient data on board Ships of Opportunity.…”

“…Mills et al, 2005) -Digiscan(Plant et al, 2009) -ANAIS(Thouron et al, 2003) -Alchemist (LeBris et al, 2000) -CHEMINI(Vuillemin et al, 2009a) -LoC(Beaton, 2012;Nightingale et al, 2015;Beaton et al, 2017;Clinton-Bailey et al, 2017;Grand et al, 2017;Vincent et al, 2018…”