A new ion source for liquid chromatography/thermospray mass spectrometry with a magnetic sector field mass spectrometer

A new and simple ion source for thermospray on a sector field mass spectrometer has been designed, which is based on two sets of electrostatic quadrupole lenses to focus the divergent ion beam that emanates from the extraction cone into the ion source region. To illustrate the performance of the source, the on‐line separation and detection of a few samples are shown using scanning and single‐ion monitoring techniques. Examples are a mixture of phena‐zines and samples of caffeine and adenosine. With single ion motoring, 5 ng of a phenazine, 300 pg of caffeine and ∼1 ng of adenosine were detected. Further, it is shown that declustering and collision‐induced fragmentation occur inside the sampling cone, resulting in peak broadening on the low‐mass side of signals of protonated species. Minimizing the collision‐induced dissociation of erythromycin was used to optimize the flow‐rate of the liquid chromatograph and the pressure in the source housing.