Supercritical Fluid Nanospray Mass Spectrometry

Area of Science:

• Analytical Chemistry
• Mass Spectrometry
• Supercritical Fluid Technology

Background:

• Traditional electrospraying of supercritical fluids (SF) often uses organic solvent makeup flow, leading to sample dilution and reduced sensitivity.
• Premixing SF with organic solvents can improve electrospray efficiency and analyte charge state, but presents challenges.

Purpose of the Study:

• To develop and evaluate a novel nanospray mass spectrometry (nSF-MS) system for supercritical fluids.
• To overcome limitations of conventional SF electrospray methods, aiming for enhanced sensitivity and efficiency.

Main Methods:

• A split-flow nSF-MS system was designed using small-bore capillaries, a heated interface, inline frit, and submicron emitter tips.
• Quaternary alkyl amines in supercritical CO2 with a 10% methanol modifier were electrosprayed and analyzed.
• Analyte signal response was assessed across varying flow rates, linear flow rates, and pressure ranges.

Main Results:

• The nSF system demonstrated mass-sensitive detection, with signal intensity increasing with capillary inner diameter and analyte injection volume.
• A 10-fold signal intensity enhancement was observed compared to conventional SF makeup flow electrospray ionization (ESI).
• Carrier additives generally reduced signal intensity, suggesting efficient solvent evaporation is key.

Conclusions:

• The developed nSF-MS system effectively enhances mass spectrometry detection sensitivity for supercritical fluid analysis.
• Rapid solvent evaporation at the emitter point, facilitated by nanoemitters and low modifier percentages, is crucial for improved sensitivity.
• This system offers a promising alternative for analyzing analytes in supercritical fluids with increased efficiency.