Determination of dissolved zinc in seawater using micro-Sequential Injection lab-on-valve with fluorescence detection

Area of Science:

• Analytical Chemistry
• Environmental Science
• Microfluidics

Background:

• Accurate determination of trace metals like zinc (Zn2+) in seawater is crucial for environmental monitoring.
• Traditional methods often require sample preconcentration or acidification, complicating shipboard analysis.
• Lab-on-valve (LOV) systems offer miniaturization and automation potential for complex analytical tasks.

Purpose of the Study:

• To design and optimize a micro-Sequential Injection lab-on-valve (μSI-LOV) system for direct trace Zn2+ determination.
• To evaluate the impact of sample and reagent sequencing on analytical sensitivity and signal quality.
• To achieve low detection limits for Zn2+ in an unacidified seawater matrix suitable for open ocean studies.

Main Methods:

• Development of a μSI-LOV system integrated with fluorescence detection using FluoZin-3.
• Systematic optimization of reaction conditions, blank signal sources, and physical μSI-LOV parameters.
• Investigation of sample and reagent aspiration order for maximizing sensitivity and peak shape.

Main Results:

• Optimized μSI-LOV protocol achieved a Zn2+ detection limit of 0.3 nM with high precision (RSD < 2.5%).
• Aspirating a larger sample volume (75 μL) last in the sequence yielded the best peak shape and sensitivity.
• The system demonstrated a linear quantification range up to 40 nM with a rapid analytical cycle of ~1 minute per sample.

Conclusions:

• The μSI-LOV system successfully enables direct trace Zn2+ determination in unacidified seawater, approaching open ocean requirements.
• The optimized system offers low reagent consumption, full automation, and minimal maintenance, ideal for shipboard and unattended monitoring.
• This μSI-LOV approach provides a robust platform for advancing trace element analysis in challenging environmental matrices.