Lab-on-chip measurement of nitrate and nitrite for in situ analysis of natural waters.

Microfluidic technology permits the miniaturization of chemical analytical methods that are traditionally undertaken using benchtop equipment in the laboratory environment. When applied to environmental monitoring, these "lab-on-chip" systems could allow high-performance chemical analysis methods to be performed in situ over distributed sensor networks with large numbers of measurement nodes. Here we present the first of a new generation of microfluidic chemical analysis systems with sufficient analytical performance and robustness for deployment in natural waters. The system detects nitrate and nitrite (up to 350 μM, 21.7 mg/L as NO(3)(-)) with a limit of detection (LOD) of 0.025 μM for nitrate (0.0016 mg/L as NO(3)(-)) and 0.02 μM for nitrite (0.00092 mg/L as NO(2)(-)). This performance is suitable for almost all natural waters (apart from the oligotrophic open ocean), and the device was deployed in an estuarine environment (Southampton Water) to monitor nitrate+nitrite concentrations in waters of varying salinity. The system was able to track changes in the nitrate-salinity relationship of estuarine waters due to increased river flow after a period of high rainfall. Laboratory characterization and deployment data are presented, demonstrating the ability of the system to acquire data with high temporal resolution.

[1]  Gillian M. Greenway,et al.  Characterisation of a micro-total analytical system for the determination of nitrite with spectrophotometric detection , 1999 .

[2]  Y. Shim,et al.  Simultaneous analysis of nitrate and nitrite in a microfluidic device with a Cu‐complex‐modified electrode , 2006, Electrophoresis.

[3]  Tommy D. Dickey,et al.  Initial results from the Bermuda Testbed Mooring program , 1998 .

[4]  P. Mozetič,et al.  Phytoplankton responses to freshwater inputs in a small semi-enclosed gulf (Gulf of Trieste, Adriatic Sea) , 1995 .

[5]  Véronique Garçon,et al.  An autonomous nutrient analyzer for oceanic long-term in situ biogeochemical monitoring. , 2003, Analytical chemistry.

[6]  L. Cahoon,et al.  Short-term variability of water quality parameters in two shallow estuaries of North Carolina , 1999 .

[7]  P. Dorval,et al.  CHEMINI: A new in situ CHEmical MINIaturized analyzer , 2009 .

[8]  Paul J Worsfold,et al.  Nitrogen cycling in natural waters using in situ, reagentless UV spectrophotometry with simultaneous determination of nitrate and nitrite. , 2007, Environmental science & technology.

[9]  Wolfgang Frenzel,et al.  Re-Examination of the Cadmium Reduction Method and Optimisation of Conditions for the Determination of Nitrate by Flow Injection Analysis , 2004 .

[10]  David M. Karl,et al.  Nitrate supply from deep to near-surface waters of the North Pacific subtropical gyre , 2010, Nature.

[11]  P. Worsfold,et al.  Flow injection determination of nitrate in estuarine and coastal waters , 1994 .

[12]  J. Lambert,et al.  Differential Colorimetric Determination of Nitrite and Nitrate lons , 1960 .

[13]  R. Compton,et al.  Detection and determination of nitrate and nitrite: a review. , 2001, Talanta.

[14]  Richard G. Compton,et al.  Electrochemical detection of nitrate and nitrite at a copper modified electrode , 2000 .

[15]  F. Nydahl.  On the optimum conditions for the reduction of nitrate to nitrite by cadmium. , 1976, Talanta.

[16]  M. S. Finch,et al.  A low power ultra violet spectrophotometer for measurement of nitrate in seawater: introduction, calibration and initial sea trials , 1998 .

[17]  SONUS: The Southern Nutrients Study 1995-1997 , 1999 .

[18]  Danielle R. Greenhow,et al.  High-resolution in situ analysis of nitrate and phosphate in the oligotrophic ocean. , 2007, Environmental science & technology.

[19]  Matthew C. Mowlem,et al.  Reduction of surface roughness for optical quality microfluidic devices in PMMA and COC , 2010 .

[20]  K. Johnson,et al.  Continuous determination of nitrate concentrations in situ , 1989 .

[21]  H. Melling,et al.  Correcting Nitrate Profiles Measured by the In Situ Ultraviolet Spectrophotometer in Arctic Ocean Waters , 2009 .

[22]  Kenneth S. Johnson,et al.  In situ ultraviolet spectrophotometry for high resolution and long-term monitoring of nitrate, bromide and bisulfide in the ocean , 2002 .

[23]  Hywel Morgan,et al.  Nanomolar detection with high sensitivity microfluidic absorption cells manufactured in tinted PMMA for chemical analysis. , 2011, Talanta.

[24]  J. P. Riley,et al.  The spectrophotometric determination of nitrate in natural waters, with particular reference to sea-water , 1953 .

[25]  Jordi Bartrolí,et al.  Microflow injection system based on a multicommutation technique for nitrite determination in wastewaters. , 2006, The Analyst.

[26]  M. Brzezinski,et al.  New Chemical, Bio-Optical and Physical Observations of Upper Ocean Response to the Passage of a Mesoscale Eddy Off Bermuda , 1999 .

[27]  Adrian P. Martin,et al.  A Novel Integration of an Ultraviolet Nitrate Sensor On Board a Towed Vehicle for Mapping Open-Ocean Submesoscale Nitrate Variability , 2010 .

[28]  D. Diamond,et al.  Wireless sensor networks and chemo-/biosensing. , 2008, Chemical reviews.

[29]  John Gould,et al.  Argo profiling floats bring new era of in situ ocean observations , 2004 .

[30]  K. Lau,et al.  Validation of a fully autonomous phosphate analyser based on a microfluidic lab-on-a-chip. , 2010, Water science and technology : a journal of the International Association on Water Pollution Research.

[31]  Matthew C. Mowlem,et al.  An automated microfluidic colourimetric sensor applied in situ to determine nitrite concentration , 2011 .

[32]  Dominique Birot,et al.  A new chemical analyzer for in situ measurement of nitrate and total sulfide over hydrothermal vent biological communities , 2000 .

[33]  Gillian M. Greenway,et al.  The development of an on-chip micro-flow injection analysis of nitrate with a cadmium reductor , 2001 .

[34]  A. Edwards,et al.  Rainfall events and their influence on nutrient distributions in the Ythan Estuary (Scotland) , 1997 .

[35]  Carole M. Sakamoto,et al.  Improved algorithm for the computation of nitrate concentrations in seawater using an in situ ultraviolet spectrophotometer , 2009 .

[36]  D. C. Webb,et al.  SLOCUM: an underwater glider propelled by environmental energy , 2001 .

[37]  N Avdalovic,et al.  Ion chromatography on-chip. , 2001, Journal of chromatography. A.

[38]  A. Hanson,et al.  A new in situ chemical analyzer for mapping coastal nutrient distributions in real time , 2000, OCEANS 2000 MTS/IEEE Conference and Exhibition. Conference Proceedings (Cat. No.00CH37158).

[39]  F. A. Richards,et al.  Determination of nitrate in sea water by cadmium-copper reduction to nitrite , 1967, Journal of the Marine Biological Association of the United Kingdom.

[40]  H. Paerl,et al.  Regulation of estuarine primary production by watershed rainfall and river flow , 1993 .

[41]  Stephen C. Riser,et al.  Chemical Sensor Networks for the Aquatic Environment , 2007 .

[42]  Matthew C. Mowlem,et al.  Determination of nitrate and phosphate in seawater at nanomolar concentrations , 2008 .

[43]  Carole M. Sakamoto,et al.  Submersible, Osmotically Pumped Analyzer for Continuous Determination of Nitrate in situ , 1994 .

[44]  K. Uchiyama,et al.  A polymeric master replication technology for mass fabrication of poly(dimethylsiloxane) microfluidic devices , 2005, Electrophoresis.

[45]  Matthew C. Mowlem,et al.  Microfluidic colourimetric chemical analysis system: application to nitrite detection. , 2010 .

[46]  K. Takeda,et al.  Determination of nitrate in natural waters with the photo-induced conversion of nitrate to nitrite , 1993 .

[47]  M. Mowlem,et al.  Temporal optimization of microfluidic colorimetric sensors by use of multiplexed stop-flow architecture. , 2011, Analytical chemistry.

[48]  P. Tréguer,et al.  A submersible flow-injection analyser for the in-situ determination of nitrite and nitrate in coastal waters , 1995 .

[49]  Dermot Diamond,et al.  Autonomous microfluidic system for phosphate detection. , 2007, Talanta.

[50]  A. Fischer,et al.  Corn leaf nitrate reductase--a nontoxic alternative to cadmium for photometric nitrate determinations in water samples by air-segmented continuous-flow analysis. , 2002, Environmental science & technology.

[51]  J. D. Winefordner,et al.  Limit of detection. A closer look at the IUPAC definition , 1983 .

[52]  Kenneth S. Johnson,et al.  Mapping the spatial variability of plankton metabolism using nitrate and oxygen sensors on an autonomous underwater vehicle , 2008 .

[53]  Paul J. Worsfold,et al.  An automated spectrophotometric field monitor for water quality parameters: determination of nitrate , 1987 .

[54]  E. Orive,et al.  Day-to-day variability in the plankton community of a coastal shallow embayment in response to changes in river runoff and water turbulence , 1990 .

[55]  James Davis,et al.  Current strategies in nitrite detection and their application to field analysis. , 2002, Journal of environmental monitoring : JEM.

[56]  Dermot Diamond,et al.  Autonomous field-deployable device for the measurement of phosphate in natural water , 2007, SPIE Optics East.

[57]  D. Kaniansky,et al.  Determination of Chloride, Nitrate, Sulfate, Nitrite, Fluoride, and Phosphate by Online Coupled Capillary Isotachophoresis-Capillary Zone Electrophoresis with Conductivity Detection , 1994 .

[58]  Ali Mohammad Haji Shabani,et al.  Field measurement of nitrate in marine and estuarine waters with a flow analysis system utilizing on-line zinc reduction. , 2011, Talanta.

[59]  C. Slater,et al.  An Autonomous Microfluidic Sensor for Phosphate: On-Site Analysis of Treated Wastewater , 2008, IEEE Sensors Journal.

[60]  O. Zielinski,et al.  A new nitrate continuous observation sensor for autonomous sub-surface applications: Technical design and first results , 2007, OCEANS 2007 - Europe.