Continuous Flow with Reagent Injection on an Inlaid Microfluidic Platform Applied to Nitrite Determination.

Area of Science:

• Environmental Science
• Analytical Chemistry
• Microfluidics

Background:

• High-frequency monitoring of marine nutrients is vital for understanding ecosystem impacts.
• Existing in-situ systems struggle with high reagent consumption and limited deployment times.
• Nitrite fluctuations are key indicators of marine environmental health.

Purpose of the Study:

• To develop a novel microfluidic platform for continuous, high-frequency nitrite determination in marine environments.
• To minimize reagent consumption while maintaining accurate measurements for in-situ applications.
• To overcome limitations of current systems for nutrient monitoring.

Main Methods:

• A microfluidic device utilizing automatic colorimetric absorbance spectrophotometry (Griess assay) was developed.
• The system incorporates solenoid valves, syringes, LEDs, photodiodes, and an inlaid microfluidic technique.
• Taylor-Aris dispersion was simulated and experimentally validated; signal processing mitigated refractive index differences.

Main Results:

• The microfluidic system achieved a sampling frequency of at least 10 samples per hour with significantly reduced reagent consumption.
• A limit of detection of 94 nM and a limit of quantification of 312 nM were determined for nitrite.
• Calibration curves showed good agreement with literature values for attenuation coefficients.

Conclusions:

• The developed microfluidic platform offers a viable solution for high-frequency, low-reagent nitrite monitoring in marine ecosystems.
• The system's design facilitates in-situ measurements, enabling better understanding of nutrient dynamics.
• Future work includes packaging the device for submersible deployment in marine environments.