Nano-Spray Ionization Source Isolation on Proteomic Mass Spectrometers for Siloxane Contaminant Removal

Abstract

Direct infusion experiments of Glu-Fibrinopeptide showed a non-stationarity in the signal that appeared to be inversely related to the presence of low mass contaminants, later determined to be polysiloxanes. Monitoring of these contaminants revealed a cyclical temporal profile with a period of approximately 22 minutes. This particular contaminant had the effect of suppressing peptides present at the same time. Further investigation led to the suspected source of the contaminant, the HVAC unit in the building which was also operating at a 22 minutes period. It was suspected that the polysiloxane contaminants ionize by contacting either the high voltage ionization needle or ionized sample. This led to the design and construction of an enclosure to isolate the mass spectrometer’s ionization source from the surrounding atmosphere. An airtight enclosure mounted against the inlet of the mass spectrometer effectively sealed off the front end of the instrument. A small port was connected to an activated carbon cartridge to filter the incoming air from contaminants. This design had the effect of removing the polysiloxane from the air, without introducing turbulence or detrimentally impacting the intensity of the signal.