Atmospheric pressure thermospray ionization using a heated microchip nebulizer.

Area of Science:

• Analytical Chemistry
• Mass Spectrometry
• Ionization Techniques

Background:

• Atmospheric pressure ionization techniques like APCI and APPI are standard in mass spectrometry.
• Atmospheric pressure thermospray ionization (APTSI) is an underutilized ionization phenomenon.
• Miniaturization of ionization sources offers potential advantages in sensitivity and sample consumption.

Purpose of the Study:

• To miniaturize and evaluate atmospheric pressure thermospray ionization (APTSI) using a microchip nebulizer.
• To investigate the performance of microchip-APTSI (microAPTSI) for various compounds.
• To compare microAPTSI with established ionization techniques like ESI and APCI.

Main Methods:

• Development of a microchip-based nebulizer for APTSI.
• Optimization of microAPTSI parameters including chip positioning, temperature, and gas flow rates.
• Analysis of test compounds and comparison of mass spectra with ESI and APCI.

Main Results:

• MicroAPTSI successfully ionized various compounds using only heat and gas flow.
• The technique produced ESI-like mass spectra with low background noise, favoring protonated/deprotonated molecules.
• MicroAPTSI demonstrated tolerance to mobile phase additives like TFA, unlike ESI, and enabled multiple charging of peptides without fragmentation.

Conclusions:

• Microchip-APTSI is a viable and novel alternative ionization technique for mass spectrometry.
• The microAPTSI source is compatible with standard mass spectrometer hardware.
• This miniaturized approach offers unique advantages over existing interfacing techniques, particularly in its tolerance to mobile phase additives.