Single Particle Analyzer of Mass: A Charge Detection Mass Spectrometer with a Multi-Detector Electrostatic Ion Trap

Abstract

A new charge detection mass spectrometer that combines array detection and electrostatic ion trapping to repeatedly measure the masses of single ions is described. This instrument has four detector tubes inside an electrostatic ion trap with conical electrodes (cone trap) to provide multiple measurements of an ion on each pass through the trap resulting in a signal gain over a conventional trap with a single detection tube. Simulations of a cone trap and a dual ion mirror trap design indicate that more passes through the trap per unit time are possible with the latter. However, the cone trap has the advantages that ions entering up to 2 mm off the central axis of the trap are still trapped, the trapping time is less sensitive to the background pressure, and only a narrow range of energies are trapped so it can be used for energy selection. The capability of this instrument to obtain information about the molecular weight distributions of heterogeneous high molecular weight samples is demonstrated with 8 MDa polyethylene glycol (PEG) and 50 and 100 nm amine modified polystyrene nanoparticle samples. The measured mass distribution of the PEG sample is centered at 8 MDa. The size distribution obtained from mass measurements of the 100 nm nanoparticle sample is similar to the size distribution obtained from transmission electron microscopy (TEM) images, but most of the smaller nanoparticles observed in TEM images of the 50 nm nanoparticles do not reach a sufficiently high charge to trigger the trap on a single pass and be detected by the mass spectrometer. With the maximum trapping time set to 100 ms, the charge uncertainty is as low as ±2 charges and the mass uncertainty is approximately 2% for PEG and polystyrene ions.

Direct observation of ion emission from charged aqueous nanodrops: effects on gaseous macromolecular charging

“…Charge detection mass spectrometry (CDMS) can weigh individual ions well into the 100's of megadaltons (MDa) corresponding to molecules or molecular assemblies with diameters over 100 nm. [34][35][36][37][38][39][40] Sample heterogeneity and salt adduction can lead to overlapping ion signals that can prevent conventional mass spectrometry measurements of ion ensembles. 41,42 This problem with high sample heterogeneity is overcome with CDMS measurements of individual ions, making it an ideal technique for probing charged nanodrops.…”

Mass and charge distributions of amyloid fibers involved in neurodegenerative diseases: mapping heterogeneity and polymorphism

“… 35 , 36 Single-molecule CDMS technique, where mass and charge are measured simultaneously, has previously been used for DNA, polymers and various virus capsids. 37 – 45 In our previous study, samples containing a single population of amyloid fibrils have been characterized. 27 This provided important information about amyloid fibrils, such as their mass, charge density and the number of proteins involved.…”

The aerosol impact spectrometer: a versatile platform for studying the velocity dependence of nanoparticle-surface impact phenomena

“…The image charge waveform also yields the particle time-of-flight (TOF) and velocity through the pickup providing the mass-to-charge ratio for fixed energy particles [15]. This method has been used in accelerator experiments since at least 1960 [9], and with the increasing interest in studies of massive biomolecules, cells and nanoparticles it has seen more recent applications in mass spectrometry measurements [16][17][18][19][20][21][22][23][24], with the state of the art recently described by Keifer and Jarrold [25]. In our own laboratory, we make use of a variant of this approach, applying a charge-pickup electrode in an electrostatic fast-ion beam trap to monitor the ion density oscillating in the trap and carry out Fourier-transform (FT) mass spectrometry on ensembles of molecular ions [26,27].…”