Abstract
Hadamard transform time-of-flight mass spectrometry (HT-TOFMS) is based on the pseudorandom gating of ion packets into a time-of-flight mass-to-charge analyzer. In its typical implementation, the technique is able to monitor continuous ion sources with a 50% duty cycle, independent of all other figures of merit. Recently, we have demonstrated that the duty cycle can be extended to 100% using patterned, two-channel detection. Two-channel HT-TOFMS involves the simultaneous optimization of paired one-channel experiments and imposes more stringent conditions to achieve high-quality spectra. An ion modulation device, known as Bradbury-Nielson Gate (BNG), is central to HT-TOFMS. It is an ideal deflection plate, capable of transmitting or deflecting an ion beam according to a known binary sequence without changing the times-of-flight of the ions. Analytical equations are derived that accurately describe the ion modulation process of the BNG as confirmed by good agreement with SimIon simulations and ion beam imaging experiments. From these expressions, the duty cycle and ion modulation efficiency were calculated for various BNG parameters, ion beam characteristics, and detector dimensions, which permit the optimum conditions to be chosen for the two-channel experiment. We conclude that the outer detector should be three times the maximum deflection angle to detect all deflected ions (100% duty cycle) and that the difference between the modulated ion counts in the sequence elements 0 and 1 should be maximized to achieve high modulation efficiency. This condition is best achieved by tight focusing of the ion beam in the center of the inner detector. When both channels are optimized, the two-channel advantage can be exploited to achieve a further improvement over a single-channel experiment.
Article PDF
Similar content being viewed by others
References
Zare, R. N.; Fernandez, F. M.; Kimmel, J. R. High-Speed Mass Spectrometry Hadamard Transform Time-of-Flight Mass Spectrometry: More Signal, More of the Time. Angew. Chem. Int. Ed. 2003, 42, 30–35.
Trapp, O.; Kimmel, J. R.; Yoon, O. K.; Zuleta, I. A.; Fernandez, F. M.; Zare, R. N. Continuous Two-Channel Time-of-Flight Mass Spectrometric Detection of Electrosprayed Ions. Angew. Chem. Int. Ed. 2004, 43, 6541–6544.
Guilhaus, M.; Selby, D.; Mlynski, V. Orthogonal Acceleration Time-of-Flight Mass Spectrometry. Mass Spectrom. Rev. 2000, 19, 65–107.
Verentchikov, A. N.; Ens, W.; Standing, K. G. Reflecting Time-of-Flight Mass Spectrometer with an Electrospray Ion Source and Orthogonal Extraction. Anal. Chem. 1994, 66, 126–133.
Kimmel, J. R.; Yoon, O. K.; Zuleta, I. A.; Trapp, O.; Zare, R. N. Peak Height Precision in Hadamard Transform Time-of-Flight Mass Spectra. J. Am. Soc. Mass Spectrom. 2005, 16, 1117–1130.
Bradbury, N. E.; Nielsen, R. A. Absolute Values of the Electron Mobility in Hydrogen. Phys. Rev. 1936, 49, 388–393.
Kimmel, J. R.; Engelke, F.; Zare, R. N. Novel Method for the Production of Finely Spaced Bradbury-Nielson Gates. Rev. Sci. Instrum. 2001, 72, 4354–4357.
Harwit, M. D.; Sloane, N. J. Hadamard Transform Optics; Academic Press: London, 1979, pp 55–61.
Trapp, O.; Pearce, E. W.; Kimmel, J. R.; Yoon, O. K.; Zuleta, I. A.; Zare, R. N. A. Soft On-Column Metal Coating Procedure for Robust Sheathless Electrospray Emitters Used in Capillary Electrophoresis/Mass Spectrometry. Electrophoresis 2005, 26, 1358–1365.
Bethe, H. Über den Durchgang von Kathodenstrahlen durch Gitterförmige Elektrische Felder. Z. Phys. 1929, 54, 703–710.
Yang, Z. Performance Advantages of Maximum Likelihood Methods in PRBS-Modulated Time-of-Flight Electron Energy Loss; Ph.D. Thesis, University of Maine, Orono, ME, 2003, pp 37–39.
Sedlacek, M. Electron Physics of Vacuum and Gaseous Devices; Wiley and Sons: New York, 1996, p. 103.
Dahl, D. A. SIMION for the Personal Computer in Reflection. Int. J. Mass Spectrom. 2000, 200, 3–25.
Brock, A.; Rodriguez, N.; Zare, R. N. Characterization of a Hadamard Transform Time-of-Flight Mass Spectrometer. Rev. Sci. Instrum. 2000, 71, 1306–1318.
Rodriguez, N. Hadamard Transform Time-of-Flight Mass Spectrometry: Implementation and Characteristics; Ph.D. Thesis, Stanford University, Stanford, CA, 1999.
Author information
Authors and Affiliations
Corresponding author
Additional information
Published online September 29, 2005
An erratum to this article is available at http://dx.doi.org/10.1007/BF03215900.
Rights and permissions
About this article
Cite this article
Yoon, O.K., Zuleta, I.A., Kimmel, J.R. et al. Duty cycle and modulation efficiency of two-channel hadamard transform time-of-flight mass spectrometry. J Am Soc Mass Spectrom 16, 1888–1901 (2005). https://doi.org/10.1016/j.jasms.2005.07.025
Received:
Revised:
Accepted:
Issue Date:
DOI: https://doi.org/10.1016/j.jasms.2005.07.025