Highly sensitive trace analysis of paraquat using a surface-enhanced Raman scattering microdroplet sensor

Area of Science:

• Analytical Chemistry
• Environmental Science
• Materials Science

Background:

• Paraquat (PQ) is a widely used herbicide with significant toxicity.
• Accurate and sensitive detection of PQ in environmental samples is crucial for monitoring and risk assessment.
• Existing analytical methods for PQ detection often lack the required sensitivity or speed.

Purpose of the Study:

• To develop a rapid and highly sensitive trace analysis method for paraquat (PQ) in water.
• To utilize a surface-enhanced Raman scattering (SERS)-based microdroplet sensor for PQ detection.
• To overcome limitations of conventional analytical methods in terms of sensitivity and memory effects.

Main Methods:

• A microfluidic system was employed to create microdroplets containing PQ, silver nanoparticles, and NaCl.
• A continuous oil phase encapsulated the aqueous droplets, isolating them and preventing aggregation on channel walls.
• Paraquat molecules were adsorbed onto silver nanoparticle surfaces within the isolated microdroplets.
• Surface-enhanced Raman scattering (SERS) spectroscopy was used for signal detection and quantification.

Main Results:

• The SERS-based microdroplet sensor achieved a limit of detection (LOD) for PQ below 2×10(-9) M.
• The developed sensor demonstrated enhanced sensitivity, one to two orders of magnitude higher than conventional methods.
• Complete isolation of aqueous droplets by the oil phase effectively eliminated memory effects from nanoparticle aggregates.

Conclusions:

• The SERS-based microdroplet sensor offers a rapid, highly sensitive, and robust platform for trace analysis of paraquat in water.
• This innovative approach significantly improves detection limits and mitigates common analytical challenges.
• The method holds promise for effective environmental monitoring and toxicological studies of paraquat.