Halogenated compound response in an oxygen doped ion mobility detector for capillary gas chromatography

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Abstract
An ion mobility detector that has been specifically developed for interfacing with capillary gas chromatography is investigated in the negative ion mode. Like the electron capture detector, to which this instrument is closely related, the ion mobility detector shows an enhanced response to low molecular weight halogenated compounds when a small quantity of oxygen is doped into the make‐up gas flow. Under O2 doping conditions, the device can operate in a reactant ion monitoring mode responding universally to compounds capable of capturing thermal electrons and in a tunable selective product ion mode providing increased selectivity over that achieved by the ECD. At an oxygen concentration of 0.5%, minimum detectable amounts as low as 600 femtograms have been realized for carbon tetrachloride. Selectivity of chloro‐ versus bromo‐ compounds is demonstrated using a mixture of p‐dichlorobenzene and p‐dibromobenzene.