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 HR). Here the CryoTrap-GC-AED instrumental setup is presented, and the performance for iodine (1635±135 counts I atom-1pptv-1), sulfur (409±57 counts S atom-1pptv-1), carbon (636±69 countsC atom-1pptv-1), bromine (9.1±1.8 counts Br atom-1pptv-1), and nitrogen (28±2 countsNatom-1pptv-1) emission lines is reported and discussed. The limits of detection (LODs) are in the low parts per trillion by volume 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 other VOCs. Furthermore, pressurized global whole-air samples, collected on board the Lufthansa Airbus A340-600 IAGOS-CARIBIC aircraft in the upper troposphere and lower stratosphere region, were measured with the new setup, providing data for many VOCs, including the long-lived organosulfur compound carbonyl sulfide.