A high performance microfluidic analyser for phosphate measurements in marine waters using the vanadomolybdate method

Area of Science:

• Environmental Science
• Analytical Chemistry
• Oceanography

Background:

• Accurate measurement of soluble reactive phosphorus (SRP) is crucial for understanding marine biogeochemical cycles.
• Existing portable systems for SRP determination often lack sensitivity or require complex operation.
• The vanadomolybdate method is a standard technique for phosphate analysis.

Purpose of the Study:

• To develop and validate a high-performance, autonomous analytical system for determining SRP in seawater.
• To improve the limit of detection and portability of SRP measurement systems.
• To assess the system's performance in diverse marine environments.

Main Methods:

• A microfluidic chip system was designed using tinted poly (methyl methacrylate) (PMMA).
• The system integrated a custom syringe pump, control electronics, and on-board calibration.
• The vanadomolybdate method was employed for phosphorus determination.

Main Results:

• The autonomous system demonstrated comparable results to a reference auto-analyser in coastal and open ocean waters.
• The limit of detection was improved by two orders of magnitude (52 nM) due to optical technology.
• A wide linear dynamic range (0.1–60 μM) and good precision (13.6% at 0.4 μM) were achieved.
• Silicate interferences were corrected, and a sampling throughput of up to 20 samples/hour was possible.

Conclusions:

• The developed portable micro-analytical system provides accurate, high-resolution SRP measurements in seawater.
• The system offers significant advantages in terms of sensitivity, portability, and low reagent/power consumption.
• This technology enables enhanced monitoring of phosphorus in marine ecosystems.