Microfluidic technology has great potential to fulfil the increasing demand for environmental monitoring. Through the minimisation of reagents, standard solutions and power consumption, compact autonomous instruments have been developed to perform in situ monitoring of remote locations over long deployable lifetimes.

The objective of this research is to produce autonomous chemical sensing platforms with a price performance index that creates a significant impact on the existing market. The main focus is on developing a detection platform for ammonium, nitrate and nitrite for water and wastewater using colorimetric techniques. The goal is to integrate polymer actuators valves into the microfluidic chip, to drive down the overall cost

Cleary, John

Cogan, Deirdre

Diamond, Dermot

Maher, Damien

English

Irish Universities

Next generation autonomous chemical sensors for environmental monitoring

Microfluidic technology has great potential to fulfil the increasing demand for environmental monitoring. Through the minimisation of reagents, standard solutions and power consumption, compact autonomous instruments have been developed to perform in situ monitoring of remote locations over long deployable lifetimes.\ud
The objective of this research is to produce autonomous chemical sensing platforms with a price performance index that creates a significant impact on the existing market. The main focus is on developing a detection platform for ammonium, nitrate and nitrite for water and wastewater using colorimetric techniques. The goal is to integrate polymer actuators valves into the microfluidic chip, to drive down the overall cost

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Fig 2: Benchtop nitrite detection system.  (1) Reagent storage (2) Sample storage (3) Micro-pump (4) Mixing chip (5) Detector (6) Control board (7) Battery (8) Easy-Radio (9) Waste storage. Fig 4: Prototype for next generation micro analyser platform. Micropumps based on electro-responsive polymer actuators are used to deliver sample and reagent to the LED and photodiode based optical detector. •Latest phosphate platform (fig 1) currently €200 (component cost). •Drive this to €20 by the introduction of biomimetic materials •New platform technology that can be applied to many environmental targets (fig 4).  • Minimisation /Multi-Analyser • Phosphate Sensor Deployment The system was placed in situ at Broadmeadow Water Estuary, Co. Dublin for the period 22Feb2012 - 2March2012 (fig 5).  Fig 5: Image of sensor in situ.  Fig 6: Data from the phosphate analyser and manual calibration samples (red) during the Broadmeadow trial.  Testing of the nitrite reagent chemistry set with the platform (fig 2). Absorbance is proportional to nitrite concentration at 540nm  (fig 8 & 9).   • Nitrite (NO2-)  Analyser Based on Griess Reagent  Fig 8: Cuvettes showing the change in colour intensity of nitrite samples with Griess reagent.  Fig 9: Prototype Calibration of Nitrite Standards 0-1.2mg/L • Nitrate (NO3-) Colorimetric Analysis Based on Chromotropic Acid  A yellow colour is developed when nitrate is treated with chromotropic acid in the presence of concentrated sulphuric acid (fig 10). The absorbance, measured at 430nm, is proportional  to NO3-. Calibration was done (fig 11) using UV-Vis followed by  a novel Paired Emitter-Detector Diode (PEDD) as a photometric  detector (fig 3) .       References • Diamond, D., Cleary, J., Maher, D., Kin, J. and Lau, K.T. 2011. Autonomous Analyser Platforms for Remote Monitoring of Water Quality.  • O’ Toole, M., Shepherd, R., Lau, K.T. and Diamond, D. 2007. Detection of Nitrite by flow injection analysis using a novel Paired Emitter-Detector Diode (PEDD) as a photometric Detector.   We acknowledge support for this research from The Questor Centre (grant code DCU9/11/14) and Enterprise Ireland (grant code CFTD/08/111) and also the Centre for Freshwater Studies (CFS) based in the Department of Applied Sciences at DkIT .    Fig 7: Data from the phosphate analyser during the Glaslough  trial.   Fig 11: Calibration curve of 0-80mg/L NO3-  using UV-Vis and compared to Paired Emitter-Detector Diode. Fig 10: Cuvettes showing the change in colour intensity of nitrate samples with chromotropic acid.  NEXT GENERATION AUTONOMOUS CHEMICAL SENSORS FOR ENVIRONMENTAL MONITORING  Deirdre Cogan,  John Cleary,  Damien Maher,  Dermot Diamond Dublin City University  The phosphate analyser (fig 1) is a fully integrated system incorporating fluid handling, microfluidic technology, colorimetric chemical detection, and real time wireless communications in a compact and rugged portable device. A second trial is on-going at the Integrated Constructed Wetland System in Glaslough, Co. Monaghan.  Fig 3: Paired Emitter-Detector Diode (PEDD). Microfluidic technology has great potential to fulfil the increasing demand for environmental monitoring. Through the minimisation of reagents, standard solutions and power consumption, compact autonomous instruments have been developed to perform in situ monitoring of remote locations over long deployable lifetimes.  The objective of this research is to produce autonomous chemical sensing platforms with a price performance index that creates a significant impact on the existing market. The main focus is on developing a detection platform for ammonium, nitrate and nitrite for water and wastewater using colorimetric techniques. The goal is to integrate polymer actuators valves into the microfluidic chip, to drive down the overall cost.  Fig 1: GEN2 Nutrient Analyser Design. 

NEXT GENERATION AUTONOMOUS CHEMICAL SENSORS FOR ENVIRONMENTAL MONITORING  Deirdre Cogan,  John Cleary,  Damien Maher,  Dermot Diamond Dublin City University Phosphate Sensor Deployment  • The system was placed in situ at Broadmeadow Water Estuary, Co. Dublin for the period 22Feb2012- 2March2012 (fig 4). •  This site is known to have high nutrient levels present due mostly to inputs from industry, agriculture and a wastewater treatment plant situated close by .   • A sample reading was taken in 20 minute intervals. The sensor performed 350 autonomous measurements (fig 5) and 14 manual samples were collected for lab analysis and validation.  Miniaturisation  Nitrite (NO2- ) Analyser Based on Griess Reagent  Testing of the nitrite reagent chemistry set with the platform (fig 2). Two micro pumps deliver the nitrite sample and Griess reagent through a mixing chip and through to a detector chip where the LED and photodiode measure absorbance at 540nm. Absorbance is proportional to nitrite concentration (fig 6).  NO2- levels in the samples can be established from a calibration  curve  (fig 7).   Fig 6: Cuvettes showing the change in colour intensity of 0.2 - 1.8 mg/L nitrite samples with Griess reagent. Fig 7: Prototype Calibration of Nitrite Standards 0-1.2mg/L.   Nitrate (NO3-) Colorimetric Analysis Based on Chromotropic Acid A yellow colour is developed when nitrate is treated with chromotropic acid in the presence of concentrated sulphuric acid (fig 8). The absorbance, measured at a wavelength of 430nm, is proportional  to NO3- (fig 9). Fig 8: Cuvettes showing the change in colour intensity of 0.5 – 3.5 mg/L nitrate samples with chromotropic acid reagent.  Fig 9: Calibration Curve of Nitrate standards 0-3.5mg/L. References • Diamond, D., Cleary, J., Maher, D., Kin, J. and Lau, K.T. 2011. Autonomous Analyser Platforms for Remote Monitoring of Water Quality.  • O’ Toole, M., Shepherd, R., Lau, K.T. and Diamond, D. 2007. Detection of Nitrite by flow injection analysis using a novel Paired Emitter-Detector Diode (PEDD) as a photometric Detector.  We acknowledge support for this research from The Questor Centre (grant code DCU9/11/14) and Enterprise Ireland (grant code CFTD/08/111).   Fig 4: Image of sensor in situ. Fig 5: Data from the phosphate analyser and manual calibration samples (red) during the trial. 

Microfluidic technology has great potential to fulfil the increasing demand for environmental monitoring. Through the minimisation of reagents, standard solutions and power consumption, compact autonomous instruments have been developed to perform in situ monitoring of remote locations over long deployable lifetimes.
The objective of this research is to produce autonomous chemical sensing platforms with a price performance index that creates a significant impact on the existing market. The main focus is on developing a detection platform for ammonium, nitrate and nitrite for water and wastewater using colorimetric techniques. The goal is to integrate polymer actuators valves into the microfluidic chip, to drive down the overall cost

DCU Online Research Access Service

Next Generation Autonomous Chemical Sensors for Environmental Monitoring  Deirdre Cogan, Dr. John Cleary, Dr. Damien Maher, Prof.  Dermot Diamond Dublin City University In a world where there is increasing demand for environmental monitoring, driven largely by European legislation, monitoring of remote locations has proven to be a major challenge.  Microfluidic technology has great potential as a solution to this problem as it allows minimization of reagents, standards, power consumption, and enables the development of compact autonomous instruments which can perform in situ monitoring of remote locations over long deployable lifetimes. The objective of this research is to produce next generation autonomous chemical sensing platforms with a price capability that creates a significant impact on the existing market. The projects begins with deployments of the existing phosphate platform in order to develop familiarity with all aspects of the analytical platform. Following this, the focus will be on developing a detection platform for ammonium, nitrate and nitrite in water and wastewater. The final task will be to integrate biomimetic actuators on the microfluidic platform.  Nitrite Analyser Based on Griess Reagent Testing of the nitrite reagent chemistry and detection system has been carried out using the prototype set up shown in Fig. 2. With two micro pumps delivering nitrite sample and Griess reagent through a mixing chip and hence through a detector chip where the LED and photodiode take an absorbance reading after 2 minutes.  The absorbance is proportional to nitrite concentration in the original sample. Using standards of 0.0 – 1.8 mg/L nitrite, the results are shown below in Fig. 5. The reaction time used was 2 minutes. The error bars represent ± one standard deviation with n = 5 at each concentration.  Based on this data, the detection limit of the system was determined to be approximately 0.003 mg/L.   Further Development: Nitrate/Nitrite Reduction  Following on from the excellent promise of the prototype platform, a reduction column can be introduced to enable sample nitrate to be reduced in-line to nitrite. Switching the sample line alternatively from a direct channel to the Griess reagent and detector, to a channel bringing the sample through the reduction column to the reagent and the detector enables sample nitrate to be estimated. Fig 1: First and second generation phosphate systems.  (1) Sample inlet; (2) IP68 Enclosure; (3) Reagent storage; (4) Pumps; (5) Microfluidic detection system; (6) Control board; (7) Communications. Fig 2: Benchtop nitrite detection system.  (1) Reagent storage (2) Sample storage (3) Micro-pump (4) Mixing chip (5) Detector (6) Control board (7) Battery (8) Easy-Radio (9) Waste storage. Fig 3: Prototype for next generation micro analyser platform. Micropumps based on electro-responsive polymer actuators are used to deliver sample and reagent to the LED and photodiode based optical detector. Fig 7: Cuvettes showing the change in colour intensity of 0.2 - 1.8 mg/L nitrite samples with Griess reagent that were measured with UV/Vis spectrometry shown in Fig. 6.  NO3-  + Cd + 2H+ → NO2- + Cd2+  + H2O + e-  1. NO2-  + (Griess) → Azo Colour Dye   2.  NO3-* → NO2-*  3.  (NO2-* + NO2- ) + (Griess)   4.  Steps 3-1  → NO2-* = NO3- Fig 5: Absorbance of a series of nitrite solutions measured using the nitrite detection system.   Fig 4: Reaction scheme for optical detection of nitrite using the Griess reaction. Acknowledgements  We acknowledge support for this research from The Questor Centre (grant code DCU9/11/14) and Enterprise Ireland (grant code CFTD/08/111).   Fig. 8. Reaction scheme for conversion of nitrate to nitrite using a cadmium column.   The Nitrate (NO3- ) is first reduced to nitrite (NO2-) and then total NO2- (converted NO3- plus NO2-) can be detected via colorimetric Griess reaction as seen in the prototype nitrite analyser.   Fig 6: Absorbance of a series of nitrite solutions as measured using UV/Vis spectrometry.   

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Next generation autonomous chemical sensors for environmental monitoring

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