Instrumentation, applications, and energy deposition in quadrupole ion-trap tandem mass spectrometry

Underwater mass spectrometry systems can be used for direct in situ detection of volatile organic compounds and dissolved gases in oceans, lakes, rivers and waste-water streams. In this work we describe the design and operation of (1) a linear quadrupole mass filter and (2) a quadrupole ion trap mass spectrometer interfaced, in each case, with a membrane introduction/fluid control system and packaged for underwater operation. These mass spectrometry systems can operate autonomously, or under user control via a wireless rf link. Detection limits for each system were determined in the laboratory using pure solutions. The quadrupole mass filter system provides detection limits in the 1-5 ppb range with an upper mass limit of 100 amu. Its power requirement is approximately 95 Watts. The ion trap system has detection limits well below 1 ppb, an upper mass limit of 650 amu and MS/MS capability. Its power consumption is on the order of 150 Watts. The present membrane limits analysis to non-polar compounds (Ͻ300 amu) with analysis cycles of 5-15 minutes. Deployments of both types of instruments are described, along with a discussion of the challenges associated with in-water mass spectrometry and descriptions of alternative in-water mass spectrometer configurations. (J Am Soc Mass Spectrom 2001, 12, 676 -682 ) © 2001 American Society for Mass Spectrometry S tandard methods for analysis of aqueous systems typically involve collection of samples and delivery to a laboratory for analysis [1]. Inherent in this practice is the possibility of both contamination and loss of analytes, particularly in the case of highly reactive or volatile species. In addition, this type of sampling severely limits both spatial and temporal sampling densities. A particularly important limitation of long collection/analysis cycles is the inability to implement adaptive sampling. Appropriate monitoring of dynamic biogeochemical systems requires rapid sampling adaptations in response to rapidly varying analyte distributions [2]. Intelligent sampling strategies are required to adequately characterize vast bodies of water that influence, and are influenced by, human activities. Since mass spectrometry is arguably the most versatile of chemical sensors, we have undertaken development of in situ mass spectrometry systems capable of real-time, adaptive in-water analyses.Although mass spectrometry has been used in the laboratory for an extremely wide variety of chemical analyses, from precise isotopic ratio measurements [3] to DNA sequencing [4 -6], no single configuration of mass analyzer and sample interface is appropriate for all types of measurements. This is evidenced in recent reviews of field analytical techniques [7] and advances in miniaturization of mass spectrometers [8]. Accordingly, we have chosen a modular approach for development of immersion mass spectrometers. Initially, simpler designs are used to integrate available components, and simultaneously new subsystems are being developed for evolving reconfigurations capable of accessing a w...

Section: Underwater Membrane Introduction/ion Trap Mass Spectrometer mentioning

confidence: 99%

Underwater mass spectrometers for in situ chemical analysis of the hydrosphere

Short

Fries

Kerr

et al. 2001

“…A widely used activation method is collisional activation in quadrupole ion traps [14]. This is a very slow activation method with activation times approaching a fraction of a second and with low-energy-transfer to the reactant ions [12,13].…”

mentioning

confidence: 99%

Fragmentation of protonated dipeptides containing arginine. Effect of activation method

Forbes

Jockusch

Young

et al. 2007

The fragmentation reactions of the protonated dipeptides Gly-Arg and Arg-Gly have been studied using collision-induced dissociation (CID) in a quadrupole ion trap, by in-source CID in a single-quadrupole mass spectrometer and by CID in the quadrupole cell of a QqTOF mass spectrometer. In agreement with earlier quadrupole ion trap studies (Farrugia, J. M.; O'Hair, R. A. J., Int. J. Mass Spectrom., 2003, 222, 229), the CID mass spectra obtained with the ion trap for the MH ϩ ions and major fragment ions are very similar for the two isomers indicating rearrangement to a common structure before fragmentation. In contrast, in-source CID of the MH ϩ ions and QqTOF CID of the MH ϩ , [MH Ϫ NH 3 ] ϩ and [MH Ͻ23 HN ϭ C(NH 2 ) 2 ] ϩ ions provide distinctly different spectra for the isomeric dipeptides, indicating that rearrangement to a common structure has not occurred to a significant extent under these conditions even near the threshold for fragmentation in the QqTOF instrument. Clearly, under normal operating conditions significantly different fragmentation behavior is observed in the ion trap and beam-type experiments. This different behavior probably can be attributed to the shorter observation times and concomitant higher excitation energies in the in-source and QqTOF experiments compared to the long observation times and lower excitation energies relevant to the ion trap experiments. Based largely on elemental compositions derived from accurate mass measurements in QqTOF studies fragmentation schemes are proposed for the MH ϩ , [MH Ϫ

“…With conventional resonance excitation CID ions fragment while the excitation voltage is still being applied whereas for "fast excitation" CID a higher proportion of the ions fragment in the ion cooling time following the excitation pulse. The fragmentation of the (M ϩ 17H) 17ϩ of horse heart myoglobin is also shown to illustrate the application of "fast excitation" CID to [1] by applying to the end-cap electrodes a small supplementary RF voltage, at the same secular frequency as the ion of interest. This produces an increased amplitude of ion motion for ions of that particular mass-to-charge, which then fragment after collisions with the helium buffer gas.…”

mentioning

confidence: 99%

“Fast excitation” CID in a quadrupole ion trap mass spectrometer

Murrell

Despeyroux

Lammert

et al. 2003

Collision-induced dissociation (CID) in a quadrupole ion trap mass spectrometer is usually performed by applying a small amplitude excitation voltage at the same secular frequency as the ion of interest. Here we disclose studies examining the use of large amplitude voltage excitations (applied for short periods of time) to cause fragmentation of the ions of interest. This process has been examined using leucine enkephalin as the model compound and the motion of the ions within the ion trap simulated using ITSIM. The resulting fragmentation information obtained is identical with that observed by conventional resonance excitation CID. "Fast excitation" CID deposits (as determined by the intensity ratio of the a 4 /b 4 ion of leucine enkephalin) approximately the same amount of internal energy into an ion as conventional resonance excitation CID where the excitation signal is applied for much longer periods of time. The major difference between the two excitation techniques is the higher rate of excitation (gain in kinetic energy) between successive collisions with helium atoms with "fast excitation" CID as opposed to the conventional resonance excitation CID. With conventional resonance excitation CID ions fragment while the excitation voltage is still being applied whereas for "fast excitation" CID a higher proportion of the ions fragment in the ion cooling time following the excitation pulse. The fragmentation of the (M ϩ 17H) 17ϩ of horse heart myoglobin is also shown to illustrate the application of "fast excitation" CID to [1] by applying to the end-cap electrodes a small supplementary RF voltage, at the same secular frequency as the ion of interest. This produces an increased amplitude of ion motion for ions of that particular mass-to-charge, which then fragment after collisions with the helium buffer gas. This has been the most popular method used for CID in the quadrupole ion trap mass spectrometer and has been used to study an extremely large range of species. Alternative methods for fragmenting ions within a quadrupole ion trap mass spectrometer have been reported and these include surface induced dissociation [2], photo induced dissociation [3,4], boundary activated dissociation [5][6][7], and red shift off resonance large amplitude excitation [8]. All of these methods, to a greater or lesser extent, have sought to improve the ease of performing CID, the amount of fragmentation information obtained, and the mass range of the product ion spectrum. Here we report studies aimed at increasing the speed of performing a single CID experiment. In a conventional resonance excitation CID experiment a small voltage (e.g., 1 Volt peak-peak ) is applied for a set period of time (e.g., 30 ms) followed by a short cooling time prior to analysis. Here we apply a large voltage (e.g., 20 Volts peak-peak ) for a very short period of time (e.g., 90 s) followed by a short cool time prior to analysis.