Modified ionspray interface for supercritical fluid chromatography/mass spectrometry: Interface design and initial results

A pneumatically assisted electrospray liquid chromatography/mass spectrometry interface has been modified for use with open‐tubular supercritical fluid chromatography (SFC). The modified interface houses the SFC flow restrictor within the spray device. A sheath‐flow liquid of methanol or methanol/water containing ammonium acetate flows coaxially to the restrictor. The addition of the sheath‐flow liquid results in the ionization of analytes known to be in a neutral charge state during the chromatographic separation. The sheath‐flow liquid also allows for the independent operation of the chromatograph and the mass spectrometer. Both could be operated under optimum conditions. The operation of the interface was optimized using a solution of poly(dimethylsiloxane) in CO 2 introduced by continuous infusion. We also report the application of the modified instrument to samples containing amines and propoxylated alcohols.