Properties of a new Ion Funnel

Atmospheric Pressure Ion (API) sources, inductively coupled plasma, corona discharges, lasers, electrospray and ion spray sources, are widely used in mass spectrometry. These sources create ions at atmospheric pressure. To analyze the masses of ions, they are introduced into a mass analyzer that is generally maintained at high vacuum. A differential pumping system involving several stages is commonly used to achieve high transmission efficiencies. Improved transmission through these interfaces is essential for realizing improved sensitivity. A buffer gas cooling in a RF ion guide has been previously used to improve ion transmission in API/MS [1]. However it cannot be implemented at higher than ~200 mTorr due to electric breakdown phenomena. An ion funnel has been developed at our laboratory to overcome the electrical breakdown problem and previous prototypes showed improved transmission efficiency with highmass ions, but also some discrimination against low-mass ions [2, 3]. This report presents improved results with a new ion funnel prototype.