Ion mobility studies on the negative ion-molecule chemistry of pentachloroethane

•Investigation of the negative ion-molecule chemistry of PCE in IMS and IMS-MS.•Observed product ions are Cl− and Cl−.HOO.•Product ions are observed as a doublet in a 'dry' system.•Product ions are observed as a singlet in a 'wet' system.•Care must be taken in interpreting even simple chemical systems in IMS instruments.

In this study we present an investigation of the negative ion-molecule chemistry of pentachloroethane (PCE) in air based ion mobility spectrometry and ion mobility spectrometry-mass spectrometry systems. The observed product ions are Cl−, produced by dissociative electron attachment, and Cl−·HOO resulting from a reaction with O2−. Based upon the moisture content of the system, these ions can be observed as a doublet in a 'dry' system or as a singlet in a 'wet' system. The nature of the Cl−·HOO product ion was investigated by using isoflurane (ISOF) as a probe to monitor the changing ratios of Cl− and Cl−·HOO as the PCE concentration decreased. This confirmed the origins of the two product anions. Electronic structure calculations are provided. These have aided the understanding of the reaction processes observed.

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