A cylindrical capacitor ionization source: droplet generation and controlled charge reduction for mass spectrometry

A cylindrical capacitor ionization source was used in conjunction with coro na discharge charge reduction for generation of singly charged ions for mas s spectrometric analysis. The source consists of a fused-silica capillary t hreaded with a platinum wire and placed inside a stainless steel tube. Appl ication of an electric potential to the wire results in the production of a linear stream of charged droplets when an aqueous solution is pumped throu gh the capillary. Subsequent solvent evaporation yields ions, providing a c ontinuous ion source for mass spectrometry. passage of the ions through a c orona discharge charge reduction chamber permits reduction of the charge st ate to predominantly singly charged species, facilitating analysis of DNA a nd protein mixtures. The change from production of multiply charged ions to production of singly charged ions is extremely simple, requiring only modu lation of the voltage applied to the corona discharge electrode. A simple t echnique for construction of the ionization source is reported. Copyright ( C) 2001 John Wiley & Sons, Ltd.