SYNCHRONISED VARIATION OF SOURCE CONDITIONS OF AN ATMOSPHERIC PRESSURE CHEMICAL IONISATION MASS SPECTROMETER COUPLED TO A GAS CHROMATOGRAPH TO IMPROVE STABILITY DURING ANALYSIS

摘要

A mass spectrometer is disclosed comprising a gas chromatography separation device, an atmospheric pressure ionisation ion source and a control system arranged and adapted: (i) 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 (ii) to operate 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.