An external secondary ion source for fourier transform mass spectrometry

AbstractA differentially pumped external secondary ion source for Fourier transform mass spectrometry is described. Installation does not interfere with other experiments such as laser desorption or photodissociation. Spectra of cesium iodide clusters (with ions up to m/z 8187), polyethylene glycol 1000, and histidine from both glycerol and dithiothreitol-dithioerythritol matrices are reported. The ion with m/z 156 from histidine was recorded with mass resolution of 160,000

A low voltage ion transport system for external ionization fourier transform mass spectrometry

AbstractAn efficient ion transport system that interfaces external ion sources with a commercial dual-cell Fourier transform mass spectrometry (FTMS) system so as to retain maximum experimental flexibility has been constructed. Electrostatic lenses were used for ion transfer with potentials less than 200 V to preclude discharges. Spectra were recorded by thermal ionization and by electrospray ionization. Other high pressure ionization methods can be easily added to the external ion source chamber, making this a general solution for ion transport into an FTMS system. The efficiency of ion transfer was measured to be approximately 30%. A pressure ratio of 105 between the external ion source chamber and the second cell has been demonstrated. The system incorporates a computer-controlled gate valve to isolate the cell regions from the external ion source chamber, permitting optimal conditions for ion injection and accumulation, and then after closing the valve, recording spectra at low pressure with high resolution. Spectra of Gramicidin S (resolution 90,000 at m/z 1164), aprotinin (resolution 410,000 at m/z 1304), and horse heart cytochrome c (resolution 50,000 at m/z 1546) are shown