| Title: | Evaluation of a New Reagent-Ion Source and Focusing Ion-Molecule Reactor for Use in Proton-Transfer-Reaction Mass Spectrometry |
| Author(s): | Krechmer J; Lopez-Hilfiker F; Koss A; Hutterli M; Stoermer C; Deming B; Kimmel J; Warneke C; Holzinger R; Jayne J; Worsnop D; Fuhrer K; Gonin M; de Gouw J; |
| Address: | "Aerodyne Research Inc. , Billerica , Massachusetts 01821 , United States. TOFWERK AG , 3600 Thun , Switzerland. Cooperative Institute for Research in Environmental Sciences , University of Colorado , Boulder , Colorado United States. Earth System Research Laboratory , NOAA , Boulder , Colorado 80305-3337 , United States. Department of Chemistry and Biochemistry , University of Colorado , Boulder , Colorado 80309 , United States. Institute for Marine and Atmospheric Research , Utrecht University , 3584 CC Utrecht , The Netherlands" |
| DOI: | 10.1021/acs.analchem.8b02641 |
| ISSN/ISBN: | 1520-6882 (Electronic) 0003-2700 (Linking) |
| Abstract: | "We evaluate the performance of a new chemical ionization source called Vocus, consisting of a discharge reagent-ion source and focusing ion-molecule reactor (FIMR) for use in proton-transfer-reaction time-of-flight mass spectrometry (PTR-TOF) measurements of volatile organic compounds (VOCs) in air. The reagent ion source uses a low-pressure discharge. The FIMR consists of a glass tube with a resistive coating, mounted inside a radio frequency (RF) quadrupole. The axial electric field is used to enhance ion collision energies and limit cluster ion formation. The RF field focuses ions to the central axis of the reactor and improves the detection efficiency of product ions. Ion trajectory calculations demonstrate the mass-dependent focusing of ions and enhancement of the ion collision energy by the RF field, in particular for the lighter ions. Product ion signals are increased by a factor of 10 when the RF field is applied (5000-18?ª+000 cps ppbv(-1)), improving measurement precision and detection limits while operating at very similar reaction conditions as traditional PTR instruments. Because of the high water mixing ratio in the FIMR, we observe no dependence of the sensitivity on ambient sample humidity. In this work, the Vocus is interfaced to a TOF mass analyzer with a mass resolving power up to 12?ª+000, which allows clear separation of isobaric ions, observed at nearly every nominal mass when measuring ambient air. Measurement response times are determined for a range of ketones with saturation vapor concentrations down to 5 x 10(4) mug m(-3) and compare favorably with previously published results for a PTR-MS instrument" |
| Notes: | "PubMed-not-MEDLINEKrechmer, Jordan Lopez-Hilfiker, Felipe Koss, Abigail Hutterli, Manuel Stoermer, Carsten Deming, Benjamin Kimmel, Joel Warneke, Carsten Holzinger, Rupert Jayne, John Worsnop, Douglas Fuhrer, Katrin Gonin, Marc de Gouw, Joost eng Research Support, Non-U.S. Gov't 2018/09/18 Anal Chem. 2018 Oct 16; 90(20):12011-12018. doi: 10.1021/acs.analchem.8b02641. Epub 2018 Oct 1" |
