Electrospray ionization interface to high pressure mass spectrometry and related methods
摘要
說(shuō)明書(shū)
In the simplest form, a drive RF signal 88d of constant RF frequency can be applied to the center electrode 33 relative to the two end cap electrodes 31, 32. The amplitude of the center electrode signal can be ramped up linearly in order to selectively destabilize different m/z of ions held within the ion trap. This amplitude ejection configuration may not result in optimal performance or resolution. However, this amplitude ejection method may be improved upon by applying a second signal differentially across the end caps 31, 32. This axial RF signal, where used, causes a dipole axial excitation that can result in the resonant ejection of ions from the ion trap when the ions' secular frequency of oscillation within the trap matches the end cap excitation frequency.
The ion trap 30 or mass filter can have an equivalent circuit that appears as a nearly pure capacitance. The amplitude of the voltage to drive the ion trap 30 may be high (e.g., 100 V-1500 Volts) and can employ a transformer coupling to generate the high voltage. The inductance of the transformer secondary and the capacitance of the ion trap can form a parallel tank circuit. Driving this circuit at resonant frequency may be desired to avoid unnecessary losses and/or an increase in circuit size.
The buffer gas can be provided as a pressurized canister of buffer gas as the source (160,
