Synchronised variation of source conditions of an atmospheric pressure chemical ionisation mass spectrometer coupled to a gas chromatograph

摘要

A mass spectrometer comprises a gas chromatography separation device, an atmospheric pressure ionisation ion source and a control system to operate the atmospheric pressure ionisation ion source at one or more first settings for a first period of time whilst one or more solvents elute from the gas chromatography separation device during a solvent front; and then operating the atmospheric pressure ionisation ion source at one or more second different settings for a second subsequent period of time whilst one or more analytes elute from the gas chromatography separation device. The atmospheric ionisation device may be a corona discharge device. The control system can vary the current or corona current as a function of time during the first period and the second period. The control system can operate the atmospheric ionisation source at one or more first settings for a first period of time upon detecting one or more substances eluting from the gas chromatography separation device and upon detecting one or more changes in an operating condition.