Measuring VOCs and HOMs with a Single Instrument: Comprehensive Analysis of Complex Gas Mixtures by Multi-Pressure Chemical Ionization Mass Spectrometry
HENNING FINKENZELLER, Aleksei Shcherbinin, Jyri Mikkilä, Jussi Kontro, Netta Vinkvist, Juha Kangasluoma, Matti P. Rissanen, University of Helsinki
Abstract Number: 642
Working Group: Instrumentation and Methods
Abstract
Multiple CIMS instrument configurations, distinguished particularly regarding the IMR pressure, have been required to analyze the complex mixture of atmospherically relevant trace gases that differ regarding chemical properties and therefore require different ionization approaches. For polar, functionalized compounds, very sensitive detection schemes are provided by high-pressure adduct-forming chemical ionization techniques (e.g., NO3--CIMS), whereas for non-functionalized, non-polar compounds, low-pressure chemical ionization techniques (e.g., PTR) have consistently demonstrated superior performance. Here, using a MION2 chemical ionization inlet and an Orbitrap Exploris 120 mass spectrometer, we present Multi-Pressure Chemical Ionization Mass Spectrometry (MPCIMS), the combination of high- and low-pressure ionization schemes in a single instrument, enabling the quantification of trace gases across compound classes from the same unaltered gas stream. We demonstrate the performance of the new methodology in a laboratory experiment employing a-pinene, a monoterpene relevant to atmospheric particle formation, where MPCIMS allows to measure the spectrum of compounds ranging from the volatile precursor hydrocarbon to highly functionalized condensable reaction products. MPCIMS carries the potential as an all-in-one method for the analysis of complex gas mixtures, reducing technical complexities and the need for multiple instruments without compromise of sensitivity.