Determining Energies and Cross Sections of Individual Ions Using Higher-Order Harmonics in Fourier Transform Charge Detection Mass Spectrometry (FT-CDMS)
A general method for in situ measurements of the energy of individual ions trapped and weighed using charge detection mass spectrometry (CDMS) is described. Highly charged (> 300 e), individual polyethylene glycol (PEG) ions are trapped and oscillate within an electrostatic trap, producing a time domain signal. A segmented Fourier transform (FT) of this signal yields the temporal evolution of the fundamental and harmonic frequencies of ion motion throughout the 500-ms trap time. The ratio of the fundamental frequency and second harmonic (HAR) depends on the ion energy, which is an essential parameter for measuring ion mass in CDMS. This relationship is calibrated using simulated ion signals, and the calibration is compared to the HAR values measured for PEG ion signals where the ion energy was also determined using an independent method that requires that the ions be highly charged (> 300 e). The mean error of 0.6% between the two measurements indicates that the HAR method is an accurate means of ion energy determination that does not depend on ion size or charge. The HAR is determined dynamically over the entire trapping period, making it possible to observe the change in ion energy that takes place as solvent evaporates from the ion and collisions with background gas occur. This method makes it possible to measure mass changes, either from solvent evaporation or from molecular fragmentation (MSn), as well as the cross sections of ions measured using CDMS.
KeywordsCharge detection mass spectrometry Ion mobility Ion energy Megadalton Collision cross section MS^n Harmonics Fourier transform
This material is based upon work supported by the National Science Foundation under CHE-1609866. The authors thank Professor Martin F. Jarrold for helpful discussions and Professor Ryan R. Julian for his innovative contributions to science.
- 12.Hendricks Jr., C. D.: Charged droplet experiments. J. Colloid Sci. 17, 249–259 (1962)Google Scholar
- 13.Stradling, G. L., Idzorek G. C., Shafer B. P., Curling Jr. H. L., Collopy M. T., Blossom A. A. H., Fuerstenau S.: Ultra-high velocity impacts: cratering studies of microscopic impacts from 3 km/s to 30 km/s. Int. J. Impact. Eng. 14, 719–727 (1993)Google Scholar
- 14.Viodé, A., Dagany, X., Kerleroux, M., Dugourd, P., Doussineau, T., Charles, L., Antoine, R.: Coupling of size-exclusion chromatography with electrospray ionization charge-detection mass spectrometry for the characterization of synthetic polymers of ultra-high molar mass. Rapid Commun. Mass Spectrom. 30, 132–136 (2016)CrossRefPubMedGoogle Scholar
- 18.Doussineau, T., Désert, A., Lambert, O., Taveau, J., Lansalot, M., Dugourd, P., Bourgeat-Lami, E., Ravaine, S., Duguet, E., Antoine, R.: Charge detection mass spectrometry for the characterization of mass and surface area of composite nanoparticles. J. Phys. Chem. C. 119, 10844–10849 (2015)CrossRefGoogle Scholar
- 30.Kukreja, A.A., Wang, J.C., Pierson, E., Keifer, D.Z., Selzer, L., Tan, Z., Dragnea, B., Jarrold, M.F., Zlotnick, A.: Structurally similar woodchuck and human hepadnavirus core proteins have distinctly different temperature dependences of assembly. J. Virol. 88, 14105–14115 (2014)CrossRefPubMedPubMedCentralGoogle Scholar
- 37.Elliott, A.G., Harper, C.C., Lin, H.-W., Susa, A.C., Xia, Z., Williams, E.R.: Simultaneous measurements of mass and collisional cross-section of single ions with charge detection mass spectrometry. Anal. Chem. 89, 7701–7708 (2017)Google Scholar
- 40.Smith, S.W.: The scientist and engineer’s guide to digital signal processing, 1st edn. California Technical Publ, Calif (1997)Google Scholar