Integrated Electrodes and Electrospray Emitter for Polymer Microfluidic Nanospray-MS Interface.

Area of Science:

• Analytical Chemistry
• Microfluidics
• Mass Spectrometry

Background:

• Microfluidic devices face challenges interfacing with mass spectrometry (MS), including dilution, fragile electrodes, and dead volumes.
• These limitations hinder optimal performance and widespread adoption of chip-MS systems.
• Existing interfaces often compromise sensitivity and stability.

Purpose of the Study:

• To develop a stable nanospray chip-MS interface.
• To integrate electrodes and a capillary emitter directly into the microfluidic chip.
• To mitigate common problems associated with current chip-MS interfaces.

Main Methods:

• Utilized a hybrid polystyrene-poly(dimethylsiloxane) (PS-PDMS) microfluidic platform.
• Incorporated an embedded electrode and a capillary emitter for nanospray ionization.
• Evaluated performance using two chip designs and direct infusion mass spectrometry.
• Demonstrated on-chip reaction capabilities, specifically glutathione oxidation.

Main Results:

• Achieved low limits of detection (LODs) for glutathione (GSH) at 9 nM and caffeine at 1 nM.
• Demonstrated high linearity with R² values of 0.996 and 0.992.
• Exhibited good sensitivity, with 12 counts/nM for GSH and 332 counts/nM for caffeine.
• Successfully performed and detected on-chip glutathione oxidation to GSSG using H₂O₂.

Conclusions:

• The developed hybrid PS-PDMS chip-MS interface offers a stable and robust nanospray solution.
• The integrated design effectively addresses challenges of dilution, electrode fragility, and dead volumes.
• The system demonstrates potential for sensitive analysis and on-chip reaction monitoring with online MS detection.