A fully integrated monolithic microchip electrospray device for mass spectrometry

Area of Science:

• Analytical Chemistry
• Microfluidics
• Mass Spectrometry

Background:

• Electrospray ionization is crucial for interfacing liquid samples with mass spectrometry.
• Current methods using pulled capillaries can suffer from reproducibility and stability issues.
• Microfluidic devices offer miniaturization and precise fluid control.

Purpose of the Study:

• To develop and characterize a novel microfabricated nozzle for electrospray from microfluidic devices.
• To evaluate the performance of the microfabricated nozzle in terms of reproducibility, stability, and sensitivity.
• To compare the microfabricated nozzle with traditional pulled capillaries for mass spectrometry applications.

Main Methods:

• Fabrication of micro nozzles using deep reactive ion etching on a monolithic silicon substrate.
• Integration of microfluidic channels and reservoirs within the silicon device.
• Interfacing the electrospray device with an atmospheric pressure ionization time-of-flight mass spectrometer.
• Testing with various solvent compositions and analyte concentrations (e.g., cytochrome c).

Main Results:

• Demonstrated nozzle diameters as small as 15 micrometers.
• Achieved nozzle-to-nozzle signal reproducibility of 12% and single-nozzle stability <4% relative standard deviation (RSD).
• Showed 1.5-3 times increased sensitivity and improved signal stability (2-4% RSD) compared to pulled capillaries.
• Reported a signal-to-noise ratio of 450:1 for 10 nM cytochrome c in water.
• Device lifetime exceeded 8 hours with a total volume <25 pL.

Conclusions:

• The microfabricated electrospray nozzle provides a reproducible, controllable, and robust platform for nano-electrospray.
• This technology offers significant advantages in sensitivity and stability over conventional pulled capillaries for mass spectrometry.
• The device is well-suited for integration with microfluidic separation systems, enabling miniaturized analytical workflows.