Collision-induced signal enhancement (CISE): The use of boundary activation to effect non-resonant CISE

Abstract

An alternative to resonant excitation collision-induced signal enhancement (CISE) is presented. This alternative utilizes boundary activation instead of resonant excitation to effect CISE and is called boundary activated collision induced signal enhancement (BA-CISE). There are three ways to effect BA-CISE to enhance the signal for an MS nϩ1 experiment. Each technique utilizes the ␤ z ϭ 0 boundary, which ions encounter from high to low mass/charge ratio. BA-CISE is shown to produce an almost 900% increase in the C 2 ion of [maltohexaose ϩ Li] ϩ . The use of a heavy collision gas in addition to the helium bath gas generally produced a signal enhancement inferior to the same experiment without the heavy gas. (J Am Soc Mass Spectrom 2002, 13, 650 -658) © 2002 American Society for Mass Spectrometry C ollision-induced signal enhancement (CISE) is a process whereby the abundance of a second generation, or higher, parent ion for an MS n experiment is increased. The signal increase occurs via two stages of excitation and subsequent dissociation of ions of higher mass/charge ratio than the next generation parent ion. The first stage of excitation/dissociation is of the n-1 generation parent ion and the second stage of excitation/dissociation is of the n-1 generation product ions of higher mass/charge ratio than the n generation parent ion. The viability of CISE as an effective technique depends on the existence of dissociation pathways from ions present in a product ion spectrum to the next generation parent ion. CISE through the use of single frequency and broadband waveform resonance excitation has been reported previously [1]. Another method to increase the kinetic energy of ions and effect dissociation to perform CISE in a quadrupole ion trap is explored in this work.Boundary activation via the manipulation of a z values has been previously investigated and characterized [2][3][4][5][6] and is the method evaluated here. a z is a parameter of the Mathieu second-order differential equations of motions of ions in a quadrupole ion trap. It is defined in equation 1 a z ϭ Ϫ16eUwhere (m) is the mass of the ion, (e) is the electronic charge, (r 0 ) and (z 0 ) are the radial and axial ion trap dimensions, respectively, (⍀) is the ac radial frequency of the trapping voltage, and (U) is the dc voltage amplitude. Since r o , z o , and ⍀ are constants of a given quadrupole ion trap, for a given mass/charge ratio, the a z value is only dependent upon the dc voltage. The other parameter in the Mathieu equations is q z and it is defined in equation 2.

Energetics and efficiencies of collision‐induced dissociation achieved during the mass acquisition scan in a quadrupole ion trap

“…Of the alternative electrodynamic approaches to on‐resonance excitation, boundary‐activated dissociation (BAD)15, 18, 25, 26 and direct current (dc) excitation27–32 have been amongst the most widely studied. BAD has the advantage that product ions spanning a wide range of m/z values can be efficiently recaptured following CID.…”