A submersible phosphate analyzer for marine environments based on inlaid microfluidics

Morgan, Sean; Luy, Edward; Furlong, Arnold; Sieben, Vincent J.

doi:10.1039/d1ay01876k

Cited by 11 publications

(16 citation statements)

References 32 publications

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“…The NP Sensor architecture is based on the orthophosphate sensor system described in our previous work (Morgan et al, 2022), with differences noted here. All alterations to the previous system that were needed to realize the combined dual-species instrument will be highlighted as such.…”

Section: Sensor Descriptionmentioning

confidence: 99%

“…Consequently, development of automated in situ sensors have focused on the most abundant fixed forms of N or P that directly limit primary production: nitrate (NO − 3 ) or dissolved orthophosphate (PO 3− 4 ). The gold-standard approaches toward nitrate and dissolved orthophosphate measurement rely on reagent-based colorimetry and have been shown to achieve nanomolar limits of detection (Murphy et al, 2021;Morgan et al, 2022). These techniques have been applied towards benchtop & portable nutrient detection platforms (McCaul et al, 2021), mixing one or several specifically crafted reagents with sample to generate a colored complex.…”

Section: Introductionmentioning

confidence: 99%

“…However, the fluid consumption rate (i.e., the volume of fluid consumed per measurement) limits the total possible number of samples before servicing; therefore, many sensors utilize microfluidics to maximize fluid efficiency. A wide array of microfluidic sensors have Frontiers in Sensors frontiersin.org been presented in recent literature, applied to measure nutrients (Clinton-Bailey et al, 2017;Beaton et al, 2022;Morgan et al, 2022), pH (Yin et al, 2021), silicate (Cao et al, 2018), or various other key ocean variables. Furthermore, these microfluidic platforms have been demonstrated to deep ocean depths (> 4,800 m) (Beaton et al, 2022), have performed thousands of samples per deployment (Grand et al, 2017), and present significant potential towards widespread ocean monitoring (Fukuba and Fujii, 2021;Li et al, 2022).…”

Section: Introductionmentioning

confidence: 99%

“…For simplicity, dissolved orthophosphate will be referred to simply as "phosphate" henceforth. Our dual chemistry "NP Sensor" is derived from a submersible phosphate analyzer architecture described in a previous publication, which was deployed in the Bedford Basin in Nova Scotia, Canada to acquire over 300 in situ dissolved orthophosphate measurements (Morgan et al, 2022) and has since been deployed for several multi-month periods. The novel NP Sensor combines the "fluid engine" of our previous design with a custom designed lab-on-chip that was built to perform two chemistries within the same instrument.…”

Section: Introductionmentioning

confidence: 99%

“…The novel NP Sensor combines the "fluid engine" of our previous design with a custom designed lab-on-chip that was built to perform two chemistries within the same instrument. Both nutrients are measured using two different reagent-based colourimetric assays: a modified Griess assay for nitrate detection via vanadium (III) chloride reduction to nitrite (Nightingale et al, 2018;Murphy et al, 2021), and the phosphomolybdenum blue (PMB) assay for phosphate (Grand et al, 2017;Morgan et al, 2022). A detailed discussion on the specificity of these assays in the context of marine environments can be found in the Supplementary Material.…”

Section: Introductionmentioning

confidence: 99%

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Two chemistries on a single lab-on-chip: Nitrate and orthophosphate sensing underwater with inlaid microfluidics

Luy

Smith²,

Grundke³

et al. 2022

Front. Sens.

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Autonomous in situ sensors are required to monitor high-frequency nutrient fluctuations in marine environments on a mass-scale. We present a submersible, dual-chemistry sensor that performs multiple colourimetric assays simultaneously on a fluid sample for multi-parameter in situ analysis. Based on a highly configurable architecture that has been successfully deployed for several multi-month periods, the sensor utilizes 10 solenoid valves, 4 syringes, 3 stepper motors, 2 LEDs, 4 photodiodes, and “inlaid” microfluidics to permit optical measurements of microliter fluid volumes. Fluid pathways are machined into a modular two-layer microfluidic lab-on-chip (LOC) fabricated from poly (methyl methacrylate) (PMMA) with two parallel inlaid optical cells of 10.4 mm and 25.4 mm path lengths (1.7 µl and 4 μl, respectively). Different LOC designs can be used to implement a wide variety of colorimetric assays. We demonstrate application of our dual-chemistry sensor towards simultaneous measurement of nitrate and dissolved orthophosphate: two nutrients fundamental to primary production. The performance of the dual-species nitrate and phosphate “NP Sensor” is characterized first in a controlled laboratory environment. Combined nutrient standards containing nitrate and phosphate concentrations ranging from 2.5 µM–100 µM NO3− and 0.25 µM–10 µM PO43− were analyzed, reporting detection limits of 97 nM NO3− and 15 nM PO43−. Calibrations were repeated under 3 fixed temperature conditions, T = 5°C, 10°C, 15°C, to determine the temperature-dependent sensitivity relations for both species needed to calculate concentrations during field deployments. Finally, an 8-day field deployment in Fish Hatchery Park, NS, Canada followed, acquiring a total of 592 nitrate and dissolved orthophosphate measurements. An on-board combined nutrient standard was measured periodically to assess the in situ accuracy of the sensor, with an average relative uncertainty of 15% across the deployment. Measured nitrate and dissolved orthophosphate levels in the river reached as high as 10 µM and 3.6 µM, respectively. Fast Fourier transform analysis suggests a strong out-of-phase relationship between measured phosphate and water level, with a shared frequency peak in both data agreeing within a 3.2% difference. This trend is due to conventional mixing at the river mouth to neighboring Bedford Basin. A spike in the measured nitrate to phosphate (N:P) ratio was also observed, synchronized to a precipitation event and indicative of runoff. The novel sensor will enable high-frequency dual-nutrient monitoring in many aquatic environments.

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Section: Sensor Descriptionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Two chemistries on a single lab-on-chip: Nitrate and orthophosphate sensing underwater with inlaid microfluidics

Luy

Smith²,

Grundke³

et al. 2022

Front. Sens.

Self Cite

View full text Add to dashboard Cite

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Recent advances and prospects in on-site spectrophotometric nutrient measurement in aquatic ecosystems

Zhu,

Fang,

et al. 2024

TrAC Trends in Analytical Chemistry

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An Automated Microfluidic Analyzer for In Situ Monitoring of Total Alkalinity

et al. 2023

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We have designed, built, tested, and deployed an autonomous in situ analyzer for seawater total alkalinity. Such analyzers are required to understand the ocean carbon cycle, including anthropogenic carbon dioxide (CO2) uptake and for mitigation efforts via monitoring, reporting, and verification of carbon dioxide removal through ocean alkalinity enhancement. The microfluidic nature of our instrument makes it relatively lightweight, reagent efficient, and amenable for use on platforms that would carry it on long-term deployments. Our analyzer performs a series of onboard closed-cell titrations with three independent stepper-motor driven syringe pumps, providing highly accurate mixing ratios that can be systematically swept through a range of pH values. Temperature effects are characterized over the range 5–25 °C allowing for field use in most ocean environments. Each titration point requires approximately 170 μL of titrant, 830 μL of sample, 460 J of energy, and a total of 105 s for pumping and optical measurement. The analyzer performance is demonstrated through field data acquired at two sites, representing a cumulative 25 days of operation, and is evaluated against laboratory measurements of discrete water samples. Once calibrated against onboard certified reference material, the analyzer showed an accuracy of −0.17 ± 24 μmol kg–1. We further report a precision of 16 μmol kg–1, evaluated on repeated in situ measurements of the aforementioned certified reference material. The total alkalinity analyzer presented here will allow measurements to take place in remote areas over extended periods of time, facilitating affordable observations of a key parameter of the ocean carbon system with high spatial and temporal resolution.

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A submersible phosphate analyzer for marine environments based on inlaid microfluidics

Abstract: In situ sensors are needed to further our understanding of phosphate flux dynamics in marine environments during short term events such as tidal cycles, algae blooms and runoff periods. Here,...

Cited by 11 publications

References 32 publications

Two chemistries on a single lab-on-chip: Nitrate and orthophosphate sensing underwater with inlaid microfluidics

Two chemistries on a single lab-on-chip: Nitrate and orthophosphate sensing underwater with inlaid microfluidics

Recent advances and prospects in on-site spectrophotometric nutrient measurement in aquatic ecosystems

An Automated Microfluidic Analyzer for In Situ Monitoring of Total Alkalinity

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