Effects of modular ion-funnel technology onto analysis of breath VOCs by means of real-time mass spectrometry

• Published in: Analytical and bioanalytical chemistry Vol. 412; no. 26; pp. 7131 - 7140
• Main Authors: Pugliese, Giovanni, Piel, Felix, Trefz, Phillip, Sulzer, Philipp, Schubert, Jochen K., Miekisch, Wolfram
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.10.2020; Springer; Springer Nature B.V
• Subjects: Adult; air; Alcohols; Aldehydes; Analytical Chemistry; Aromatic compounds; Aromatic hydrocarbons; Biochemistry; Biomarkers; Breath Tests; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Direct current; Drift tubes; electric field; Electric fields; Electric potential; electric potential difference; Electrodes; Female; Food Science; Humans; Ions; Ketones; Laboratory Medicine; Limit of Detection; Low pressure; Male; Mass spectrometry; Mass Spectrometry - methods; Mass spectroscopy; Middle Aged; Monitoring; Monitoring/Environmental Analysis; Organic compounds; Orifices; Proof of Concept Study; Radio frequency; radio waves; Reaction time; Real time; Research Paper; Scientific imaging; Sensitivity; Spectroscopy; Technology assessment; VOCs; Volatile organic compounds; Volatile Organic Compounds - analysis; Voltage; Young Adult; Austria; Real-time mass spectrometry; VOCs; Ion-funnel; PTR-ToF-MS; Breath analysis
• ISSN: 1618-2642; 1618-2650; 1618-2650
• DOI: 10.1007/s00216-020-02846-8

Proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS) is a powerful tool for real-time monitoring of trace concentrations of volatile organic compounds (VOCs). The sensitivity of PTR-ToF-MS also depends on the ability to effectively focus and transmit ions from the relatively high-pressure drift tube (DT) to the low-pressure mass analyzer. In the present study, a modular ion-funnel (IF) is placed adjacent to the DT of a PTR-ToF-MS instrument to improve the ion-focusing. IF consists of a series of electrodes with gradually decreasing orifice diameters. Radio frequency (RF) voltage and direct current (DC) electric field are then applied to the electrodes to get the ions focused. We investigated the effect of the RF voltage and DC field on the sensitivity of a pattern of VOCs including hydrocarbons, alcohols, aldehydes, ketones, and aromatic compounds. In a proof-of-concept study, the instrument operating both as normal DT (DC-mode) and at optimal IF conditions (RF-mode) was applied for the breath analysis of 21 healthy human subjects. For the range of investigated VOCs, an improvement of one order of magnitude in sensitivity was observed in RF-mode compared with DC-mode. Limits of detection could be improved by a factor of 2–4 in RF-mode compared with DC-mode. Operating the instrument in RF-mode allowed the detection of more compounds in the exhaled air compared with DC-mode. Incorporation of the IF considerably improved the performance of PTR-ToF-MS allowing the real-time monitoring of a larger number of potential breath biomarkers. Graphical abstract