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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\u20134 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.<\/jats:p>","DOI":"10.1007\/s00216-020-02846-8","type":"journal-article","created":{"date-parts":[[2020,8,31]],"date-time":"2020-08-31T13:28:29Z","timestamp":1598880509000},"page":"7131-7140","update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":9,"title":["Effects of modular ion-funnel technology onto analysis of breath VOCs by means of real-time mass spectrometry"],"prefix":"10.1007","volume":"412","author":[{"given":"Giovanni","family":"Pugliese","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Felix","family":"Piel","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Phillip","family":"Trefz","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Philipp","family":"Sulzer","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jochen K.","family":"Schubert","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Wolfram","family":"Miekisch","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"297","published-online":{"date-parts":[[2020,8,13]]},"reference":[{"key":"2846_CR1","doi-asserted-by":"crossref","unstructured":"Ellis AM, Mayhew CA. 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The other authors declare that they have no conflict of interest.","order":2,"name":"Ethics","group":{"name":"EthicsHeading","label":"Conflict of interest"}},{"value":"All experiments were performed in accordance with the guidelines laid down in the Declaration of Helsinki and approved by the ethics committee at University Medical Center Rostock.","order":3,"name":"Ethics","group":{"name":"EthicsHeading","label":"Research involving human participants"}},{"value":"Informed consent was obtained from all volunteers.","order":4,"name":"Ethics","group":{"name":"EthicsHeading","label":"Informed consent"}}]}}