Study of Controlled Atmosphere FµTP Soft Ionization Mass Spectrometry for the Detection of Volatile Organic Compounds as Potential Biomarkers in Saliva for Cancer

A new soft ionization device for mass spectrometry is presented using the Flexible Micro Tube Plasma under controlled atmospheric conditions. The Controlled Atmosphere-Flexible Micro Tube Plasma consists of the plasma source itself, connected to a gas chromatograph and a mass spectrometer using a borosilicate glass cross piece. Controlled atmosphere, for example nitrogen and/or oxygen mixture is introduced to the system to create a clean ionization environment. Reproducibility issues are discussed and solutions are presented manipulating the gas flow in the cross piece. A proof of concept is shown using a ketone mixture introduced to the mass spectrometer to optimize atmospheric conditions. Furthermore, the application of the presented device for the sensitive and non fragmenting ionization of volatile organic biomarkers relevant for cancer is carried out. Sample treatment for human saliva is described and relevant candidate biomarkers are measured in the saliva matrix, showing very good ionization efficiency and neglectable matrix effects with limits of detection below 80 ppt.