Glow flow ionization (GFI) mass spectrometry of small molecules. A comparison of a glow flow ionization source "GlowFlow" to electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI).

RATIONALE: Ionization by atmospheric pressure gas discharge has been employed for a long time in mass spectrometry. Inductively coupled plasma mass spectrometry is an exemplar, and widely used for elemental analysis. The technique has less uptake in organic mass spectrometry. We describe a simple source design that can be readily implemented in most atmospheric pressure ionization (API) systems and compare its performance with electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI).

METHODS: An in-house designed helium gas discharge source (referred to as "GlowFlow") was used on a Xevo G2-S time-of-flight mass spectrometer. The GlowFlow source was transferred to a compatible Xevo TQ-S triple quadrupole mass spectrometer using a UHPLC inlet. Its performance was compared to Waters ESI and APCI sources.

RESULTS: Preliminary results of GlowFlow on the Swansea instrument are presented to establish context and include analysis of low molecular mass polymers, benzoic and cinnamic acids. Comparison of performance on the Xevo TQ-S triple quadrupole mass spectrometer involved three test mixtures. The method limits of detection (six-mix) for positive-ion GlowFlow source were between 0.03 to 10.00 pg with good linear response over two-to-four orders of magnitude and R2 values > 0.98. The GlowFlow ionization source provided a signal intensity that was an order of magnitude greater than ESI for the atmospheric pressure gas chromatography (APGC) standard mix and ionised several compounds that ESI could not.

CONCLUSIONS: The current GlowFlow design is relatively simple to retrofit to most API systems due to its small size. The sensitivity of the GlowFlow design is typically an order of magnitude less than ESI in positive ion mode, but similar in sensitivity in negative ion mode and comparable to APCI.