Optical detection methods for mass spectrometry of macroions

Abstract

I. Introduction 00 II. Macroion Detection Methods 00 A. Energy‐Sensitive Detection 00 B. Charge‐Sensitive Detection 00 C. Photon‐Sensitive Detection 00 1. ELS 00 2. LIF 00 III Applications to Micron‐Sized and Nano‐Sized Particles 00 A. Ion Sources 00 B. Mass Analyzers 00 C. Detectors 00 1. ELS/Ellipsoidal Reflector 00 2. LIF/Ion Trap 00 IV. Conclusions and Outlook 00 Acknowledgments 00 References 00 Detection of macroions has been a challenge in the field of mass spectrometry. Conventional ionization‐based detectors, relying on production and multiplication of secondary electrons, are restricted to detection for charged particles of m/z < 1 × 106. While both energy‐sensitive and charge‐sensitive detectors have been developed recently to overcome the limitation, they are not yet in common use. Photon‐sensitive detectors are suggested to be an alternative, with which detection of macroions (or charged particles) by either elastic light scattering (ELS) or laser‐induced fluorescence (LIF) has been possible. In this article, we provide a critical review on the developments of novel optical detection methods for mass spectrometry of macroions, including both micron‐sized and nano‐sized synthetic polymers as well as high‐mass biomolecules. Design and development of new spectrometers making possible observations of the mass spectra of macroions with sizes in the range of 10–103 nm or masses in the range of 1–106 MDa are illustrated. The potential and promise of this optical approach toward macroion detection with high efficiency are discussed in practical aspects. © 2004 Wiley Periodicals, Inc.,Mass Spec Rev

Gas-Phase Fluorescence Excitation and Emission Spectroscopy of Three Xanthene Dyes (Rhodamine 575, Rhodamine 590 and Rhodamine 6G) in a Quadrupole Ion Trap Mass Spectrometer

“…Recently, our group [1][2][3][4] and several others [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] have presented works focusing upon the development, characterization and applications of instrumentation for measuring laser-induced fluorescence from molecular ions in the gas phase. The majority of these studies have used highly fluorescent molecules such as the xanthene-based rhodamine dyes.…”

“…The instrumentation developed features laser light sources coupled into trapping mass spectrometers that are used to mass-select the ion population of interest and to store the selected ion population for extended periods of time. Several types of mass spectrometers have been employed, including 3-D Paul-type quadrupole ion traps (QIT) [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17], Fourier transform ion cyclotron resonance mass spectrometers (FT-ICR-MS) [18][19][20][21][22][23], and linear radiofrequency ion traps (LIT) [24]. Detection of integrated gas-phase fluorescence has been accomplished using high-sensitivity photomultiplier tubes [5-7, 9-11, 13-17, 21-24] or avalanche photodiodes [18,19,25], while dispersed fluorescence has been measured using spectrographs with charge-coupled device (CCD) detectors [1-4, 8, 12, 22].…”

Molecular weight determination of high molecular mass (glyco)proteins using CGE‐on‐a‐chip, planar SDS‐PAGE and MALDI‐TOF‐MS

“…Today, all commercial CGE-on-a-chip protein assays are limited to a sizing range of about 250 kDa. MALDI-TOF-MS is a well-established analytical method for the MW determination of biopolymers [1][2][3][4][5][6][21][22][23]. The linear TOF mass analyzer offers a large analyzable MW range, high sensitivity and high mass accuracy, which cannot be obtained with other biochemical or electrophoretic methods so far.…”

Processing and classification of protein mass spectra

“…* Mass-dependent sensitivity: Most of the currently used ion detectors are based on the electron multiplier technology. The signal produced by these detectors depends on the speed of the ion and not on its kinetic energy (Peng, Cai, & Chang, 2004). Since all ions of the same charge have the same kinetic energy after acceleration, heavier ions are slower and produce a weaker signal (the signal intensity should approximately diminish with the inverse square root of m/z).…”