Atomic emission detector with gas chromatographic separation and cryogenic pre-concentration (CryoTrap-GC-AED) for atmospheric trace gas measurements

Abstract. A gas detection system has been developed, characterized and deployed for pressurized gas phase sample analyses and near real-time online measurements. It consists of a cryogenic pre-concentrator (CryoTrap), a gas chromatograph (GC), and a new high-resolution atomic emission detector (AED III). Here the CryoTrap–GC–AED instrumental setup is presented and the performance for iodine (1635 ± 135 counts I-atom^-1 pptv^-1), sulfur (409 ± 57 counts S-atom^-1 pptv^-1), carbon (636 ± 69 counts C-atom^-1 pptv^-1), bromine (9.1 ± 1.8 counts Br-atom^-1 pptv^-1) and nitrogen (28 ± 2 counts N-atom^-1 pptv^-1) emission lines is reported and discussed. The limits of detection (LODs) are in the low pptv range (0.5–9.7 pptv) and the signal is linear to at least 4 orders of magnitude, which makes it a suitable method for diverse volatile organic compound (VOC) measurements in the atmosphere, even in remote, unpolluted regions. The new system was utilized in a field study in a boreal forest at Hyytiälä, Finland in late summer 2016 which made monoterpene measurements possible among the other VOCs. Furthermore, pressurized global whole-air sample measurement collected onboard the Lufthansa Airbus A340-600 IAGOS-CARIBIC aircraft in the upper troposphere and lower stratosphere region was carried out with the new setup, providing the observational data of many VOCs, including the long-lived organosulfur compound carbonyl sulfide.