Multi-turn time-of-flight mass spectrometers with electrostatic sectors

Charge-Dependent Metastable Dissociations of Multiply Charged Decafluorobiphenyl Formed by Femtosecond Laser Pulses

Femtosecond laser ionization is a unique means to produce multiply charged organic molecules in the gas phase. The charge-dependent chemical reactions of such electron-deficient molecules are interesting from both fundamental and applied scientific perspectives. We have reported the production of quadruply charged perfluoroaromatics; however, they were so stable that we cannot obtain information about their chemical reactions. In general, it might be difficult to realize the conflicting objectives of observing multiply charged molecular ion themselves and their metastable dissociations. In this study, we report the first example showing metastable dissociations of several charge states within the measurable time range of a time-of-flight mass spectrometer. Metastable dissociations were analyzed by selecting a precursor ion with a Bradbury-Nielsen ion gate followed by time-of-flight analysis using a reflectron. We obtained qualitative information that triply and quadruply charged decafluorobiphenyl survived at least in the acceleration region but completely decomposed before entering a reflectron. In contrast, three dissociation channels for singly and one for doubly charged molecular ions were discriminated by a reflectron and determined with the help of ion trajectory simulations.

Development of electrostatic-induced charge detector for multiturn time-of-flight mass spectrometer

We developed an autocorrelation function to resolve the overtaking problem in a multiturn time-of-flight mass spectrometer (TOF-MS). The function analyzes the characteristic period for one lap of each ion packet and derives a mass spectrum from a signal pulse train composed of multiturn ion packets. To detect the ion pulse train, a new nondestructive ion detector was developed and installed in the multiturn orbit of MULTUM-S II. This detector is composed of an electrostatically induced charge detector, a preamplifier, and a digitizer. The electrostatic noises are smaller than the single-ion signals owing to the accumulation of the multiturn TOF spectrum. The conventional ion detector of TOF-MS is operated after collecting the signal pulse train. The multiturn TOF spectrum was convolved with an autocorrelation function to derive the mass spectrum. The convolved mass spectrum performed a mass resolving power (MRP) of 28,200 at m/z 69 and mass accuracy of 28 ppm for the perfluorotributylamine (PFTBA) gas sample.

Science Objectives for Flagship-Class Mission Concepts for the Search for Evidence of Life at Enceladus

Cassini revealed that Saturn's Moon Enceladus hosts a subsurface ocean that meets the accepted criteria for habitability with bio-essential elements and compounds, liquid water, and energy sources available in the environment. Whether these conditions are sufficiently abundant and collocated to support life remains unknown and cannot be determined from Cassini data. However, thanks to the plume of oceanic material emanating from Enceladus' south pole, a new mission to Enceladus could search for evidence of life without having to descend through kilometers of ice. In this article, we outline the science motivations for such a successor to Cassini, choosing the primary science goal to be determining whether Enceladus is inhabited and assuming a resource level equivalent to NASA's Flagship-class missions. We selected a set of potential biosignature measurements that are complementary and orthogonal to build a robust case for any life detection result. This result would be further informed by quantifications of the habitability of the environment through geochemical and geophysical investigations into the ocean and ice shell crust. This study demonstrates that Enceladus' plume offers an unparalleled opportunity for in situ exploration of an Ocean World and that the planetary science and astrobiology community is well equipped to take full advantage of it in the coming decades.

A Method for Expanding Mass Range on a Multi-Turn Time-of-Flight Mass Spectrometer by a Lap Superimposed Spectrum

A time-of-flight mass spectrometer that uses a closed-orbit flight path can achieve a high mass resolving power and a high mass accuracy with a small instrument footprint. It has long been known that a drawback to a closed flight path is an obtained spectrum may contain peaks by ions at a different number of laps. A lower m/z ion may overtake higher m/z ions, resulting in the peak being superimposed on an acquired mass spectrum; therefore, such a mass bandwidth of the analyzer is limited to a narrow range given the current situation. However, recent research has documented a solution to the problem based on careful study of the equation of motion of an ion in a closed-path analyzer. All of the ions in the analyzer remain in motion in orbit by the nature of the closed flight path, thus resulting in a superimposed spectrum with the width of the orbital period of the highest mass in the sample matrix, which contains several different lap numbers. When target ions for the sample are known in advance, the time-of-flight for a given m/z can be determined regardless of the lap number under given analyzer conditions, and peak assignment can be self-validated by comparison to a mass spectrum acquired at a different lap condition. Furthermore, the m/z value for an unknown ion can also be determined by comparing time-of-flight values on spectra acquired at different lap conditions.

Non-destructive detection of large molecules without mass limitation

The problem for molecular identification knows many solutions, which include mass spectrometers whose mass sensitivity depends on the performance of the detector involved. The purpose of this article is to show by means of molecular dynamics simulations how a laser-cooled ion cloud, confined in a linear radio-frequency trap, can reach the ultimate sensitivity providing the detection of individual charged heavy molecular ions. In our simulations, we model the laser-cooled Ca⁺ ions as two-level atoms, confined thanks to a set of constant and time oscillating electrical fields. A singly charged molecular ion with a mass of 10⁶ amu is propelled through the ion cloud. The induced change in the fluorescence rate of the latter is used as the detection signal. We show that this signal is due to a significant temperature variation triggered by the Coulomb repulsion and amplified by the radio-frequency heating induced by the trap itself. We identify the optimum initial energy for the molecular ion to be detected, and furthermore, we characterize the performance of the detector for a large range of confinement voltages.

Development of novel projection-type imaging mass spectrometer

We developed a novel imaging mass spectrometer based on our accumulating technology for projection-type imaging mass spectrometry, the simulation of an accurate ion trajectory, and the theory for ion optics. The newly developed apparatus yields high spatial resolution with a substantially shorter image-acquisition time compared with conventional scanning-type imaging mass spectrometers. In order to maintain a high mass resolution, a multi-turn time-of-flight mass spectrometer is combined with post-extraction differential acceleration methods. Consequently, a mass resolution of m/Δm ∼ 10 000 and a spatial resolution of 1 μm were achieved simultaneously in this study. Application of our newly established apparatus to biological samples accomplished successful imaging mass spectrometry by exhibiting an organ-specific distribution of endogenous ions as well as a localized distribution of exogenously applied ions with an ultra-high spatial resolution image in the size of 18.5 megapixels.

Time-of-flight mass spectrometers based on a wedge-shaped electrostatic mirror with a two-dimensional field

RATIONALE

For most of the last two decades, a considerable effort has been made towards improving time-of-flight mass spectrometry (TOF MS), which has become an irreplaceable instrumental platform for the purposes of performing analytical measurements in life sciences, such as molecular biology, proteomics, medicine, etc. This can primarily be attributed to the ability of TOF MS to rapidly detect and identify nearly any targeted chemical trace with both high precision and accuracy. However, multi-span TOF MS experiments are limited due to aberrations arising from multiple reflection; our proposed scheme will minimize these aberrations.

METHODS

The inhomogeneous accelerating field is generated without using meshes by changing the potentials on the electrodes of the mirror. The ions are extracted from the ion source by short impulse activation of the accelerating electric field. Since the ions are extracted from various points of the source, even ions with identical masses acquire different velocities during acceleration.

RESULTS

We have shown that the "rear" ions of the packet catch up with the "front" ions, and packets of ions with identical masses are compressed in the direction of their movement. It is concluded that, by placing the detector in a plane with the greatest compression of ion packets, an enhanced performance of a time-of-flight mass spectrometer is achieved.

CONCLUSIONS

We have shown that effective spatial-temporal focusing allows a small mass spectrometer to achieve high resolution and sensitivity. We also propose and numerically evaluate a new platform for designing multi-stage and multi-reflective time-of-flight analyzers with wedge-shaped mirrors. We applied the simulation results to the modernization of old equipment and showed that by simply replacing the electrostatic mirror with an optimized one, a significant increase in the analyzing power can be achieved.

Mass spectrometry and planetary exploration: A brief review and future projection

Since the inception of mass spectrometry more than a century ago, the field has matured as analytical capabilities have progressed, instrument configurations multiplied, and applications proliferated. Modern systems are able to characterize volatile and nonvolatile sample materials, quantitatively measure abundances of molecular and elemental species with low limits of detection, and determine isotopic compositions with high degrees of precision and accuracy. Consequently, mass spectrometers have a rich history and promising future in planetary exploration. Here, we provide a short review on the development of mass analyzers and supporting subsystems (eg, ionization sources and detector assemblies) that have significant heritage in spaceflight applications, and we introduce a selection of emerging technologies that may enable new and/or augmented mission concepts in the coming decades.

Measurement of Individual Ions Sharply Increases the Resolution of Orbitrap Mass Spectra of Proteins

It is well-known that with Orbitrap-based Fourier-transform-mass-spectrometry (FT-MS) analysis, longer-time-domain signals are needed to better resolve species of interest. Unfortunately, increasing the signal-acquisition period comes at the expense of increasing ion decay, which lowers signal-to-noise ratios and ultimately limits resolution. This is especially problematic for intact proteins, including antibodies, which demonstrate rapid decay because of their larger collisional cross-sections, and result in more frequent collisions with background gas molecules. Provided here is a method that utilizes numerous low-ion-count spectra and single-ion processing to reconstruct a conventional m/ z spectrum. This technique has been applied to proteins varying in molecular weight from 8 to 150 kDa, with a resolving power of 677 000 achieved for transients of carbonic anhydrase (29 kDa) with a duration of only ∼250 ms. A resolution improvement ranging from 10- to 20-fold was observed for all proteins, providing isotopic resolution where none was previously present.

A W-Geometry Ortho-TOF MS with High Resolution and Up to 100% Duty Cycle for MS/MS

Orthogonal injection time-of-flight (orthoTOF) mass spectrometry (MS) is the most prevalent form of TOFMS, owing to its greater control over incoming ion energy, the ability to correct for aberrations in incoming ion velocity and position, and its ability to provide an entire mass spectrum within a single scan. However, the duty cycle of orthoTOFMS is low compared with scanning analyzers, which can have 100% duty cycle when measuring a single type of ion. Typical duty cycles for orthoTOFMS range from 1% to 30%, depending on instrument geometry. Generally, as instrument resolution increases, duty cycle decreases. Additionally, the greatest duty cycle is achieved for the highest m/z ion recorded in the spectrum, and decreases for all other ions as a function of m/z. In a prior publication [Loboda, A.V.; Chernushevich, I.V. J. Am. Soc. Mass Spectrom. 20, 1342-1348 (20)], a novel trapping/release method for restoring the duty cycle of a V-geometry orthoTOFMS to near 100% (referred to as "Zeno pulsing") was presented. Here, we apply that method to a W-TOF geometry analyzer with analog detection. Across a m/z range of 100-2000, sensitivity gains of ~5-20 are observed, for total ion currents approaching ~10⁷ ions·s^-1. Zeno pulsing, or similar strategies for restoring duty cycle, will continue to be important as instrument resolution in orthoTOFMS is increased through the use of ion mirrors. Graphical Abstract ᅟ.

The sTOF, a Favorable Geometry for a Time-of-Flight Analyzer

A new geometry for the flight region in a time-of-flight mass spectrometer is presented. It consists of two opposing electrostatic sectors of about 255° each and straight sections with a length appropriate to the turns. The resulting geometry folds into a compact space. The first-order aberrations for position, angle, and energy are all zero. The transverse focusing properties are also excellent. For an energetic, high-divergence ion source such as laser ablation, the sTOF has higher resolution and ion transmission than a reflectron of similar physical size. Graphical Abstract ᅟ.

High Spatial Resolution Laser Desorption/Ionization Mass Spectrometry Imaging of Organic Layers in an Organic Light-Emitting Diode

To improve the durability of organic materials in electronic devices, an analytical method that can obtain information about the molecular structure directly from specific areas on a device is desired. For this purpose, laser desorption/ionization mass spectrometry imaging (LDI-MSI) is one of the most promising methods. The high spatial resolution stigmatic LDI-MSI with MULTUM-IMG2 in the direct analysis of organic light-emitting diodes was shown to obtain a detailed mass image of organic material in the degraded area after air exposure. The mass image was observed to have a noticeably improved spatial resolution over typical X-ray photoelectron spectroscopy, generally used technique in analysis of electronic devices. A prospective m/z was successfully deduced from the high spatial resolution MSI data. Additionally, mass resolution and accuracy using a spiral-orbit TOF mass spectrometer, SpiralTOF, were also investigated. The monoisotopic mass for the main component, N,N'-di-1-naphthalenyl-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (m/z 588), was measured with a mass resolution of approximately 80,000 and a mass error of about 5 mDa using an external calibrant. This high mass resolution and accuracy data successfully deduced a possible elemental composition of partially remained material in the degraded area, C₃₆H₂₄, which was determined as anthracene, 9-[1,1'-biphenyl]-4-yl-10-(2-naphthalenyl) by combining structural information with high-energy CID data. The high spatial resolution of 1 μm in LDI-MSI along with high mass resolution and accuracy could be useful in obtaining molecular structure information directly from specific areas on a device, and is expected to contribute to the evolution of electrical device durability.

Inductively Coupled Plasma Zoom-Time-of-Flight Mass Spectrometry

A zoom-time-of-flight mass spectrometer has been coupled to an inductively coupled plasma (ICP) ionization source. Zoom-time-of-flight mass spectrometry (zoom-TOFMS) combines two complementary types of velocity-based mass separation. Specifically, zoom-TOFMS alternates between conventional, constant-energy acceleration (CEA) TOFMS and energy-focused, constant-momentum acceleration (CMA) (zoom) TOFMS. The CMA mode provides a mass-resolution enhancement of 1.5-1.7× over CEA-TOFMS in the current, 35-cm ICP-zoom-TOFMS instrument geometry. The maximum resolving power (full-width at half-maximum) for the ICP-zoom-TOFMS instrument is 1200 for CEA-TOFMS and 1900 for CMA-TOFMS. The CMA mode yields detection limits of between 0.02 and 0.8 ppt, depending upon the repetition rate and integration time-compared with single ppt detection limits for CEA-TOFMS. Isotope-ratio precision is shot-noise limited at approximately 0.2% relative-standard deviation (RSD) for both CEA- and CMA-TOFMS at a 10 kHz repetition rate and an integration time of 3-5 min. When the repetition rate is increased to 43.5 kHz for CMA, the shot-noise limited, zoom-mode isotope-ratio precision is improved to 0.09% RSD for the same integration time.

Real time monitoring of gases emitted from soils using a multi-turn time-of-flight mass spectrometer "MULTUM-S II"

Many miniaturized mass spectrometers used for on-site analysis have been designed and developed recently utilizing a broad range of analyzer platforms. These instruments are expected to have widespread applications covering many fields of interest. In our laboratory, a miniaturized multi-turn time-of-flight (TOF) mass spectrometer "MULTUM-S II" was designed and constructed. The size and weight of the developed "MULTUM-S II" are 45 cm × 23 cm × 64 cm and 36 kg. Irrespective of this small platform, it still boasts a high mass resolution capability of more than 30,000. In this study, we attempted to carry out real-time monitoring of gaseous compounds such as N2, O2, CO2, N2O and CH4. Using conventional miniaturized mass spectrometers, CO2 and N2O cannot be detected simultaneously due to the low mass resolution inherent to these established analyzer designs. Using a new method, "GC/high resolution mass spectrometry" described in this paper, real time monitoring of gases emitted from soils can be achieved. In a soil incubation experiment, CO2 and N2O started to increase just after water supplement and these gases varied similarly during the experiment, thus showing that this improved gas analyzing system could monitor the short time response of gaseous production in soil.

Development of a miniaturized multi-turn time-of-flight mass spectrometer with a pulsed fast atom bombardment ion source

A miniaturized multi-turn time-of-flight (TOF) mass spectrometer with a pulsed fast atom bombardment (FAB) ion source (FAB-MULTUM) has been designed and constructed in order to overcome the drawbacks associated with magnetic sector type instruments utilizing a FAB ion source such as size and weight. This instrument consists of a pulsed FAB ion source, a multi-turn TOF mass spectrometer, a detector, vacuum system, and electronic circuits. The size and weight of the system are less than H520 mm x L580 mm x W230 mm and 45 kg (including vacuum pumps and electronic circuits). The achieved resolving power and mass accuracy of this instrument were > 25000 and about 1 ppm, respectively, which are equivalent to those of magnetic sector type instruments, although the size and weight are much smaller than those of magnetic sector type instruments. The experimental results led us to the conclusion that this instrument enables accurate mass measurements and is a powerful tool for the confirmation of synthesized compounds.

Constant-momentum acceleration time-of-flight mass spectrometry with energy focusing

Fundamental aspects of constant-momentum acceleration time-of-flight mass spectrometry (CMA-TOFMS) are explored as a means to improve mass resolution. By accelerating all ions to the same momentum rather than to the same energy, the effects of the initial ion spatial and energy distributions upon the total ion flight time are decoupled. This decoupling permits the initial spatial distribution of ions in the acceleration region to be optimized independently, and energy focus, including ion turn-around-time error, to be accomplished with a linear-field reflectron. Constant-momentum acceleration also linearly disperses ions across time according to mass-to-charge (m/z) ratio, instead of the quadratic relationship between flight time and m/z found in conventional TOFMS. Here, CMA-TOFMS is shown to achieve simultaneous spatial and energy focusing over a selected portion of the mass spectrum. An orthogonal-acceleration time-of-flight system outfitted with a reduced-pressure DC glow discharge (GD) ionization source is used to demonstrate CMA-TOFMS with atomic ions. The influence of experimental parameters such as the amplitude and width of the time-dependent CMA pulse on mass resolution is investigated, and a useful CMA-TOFMS focusing window of 2 to 18 Da is found for GD-CMA-TOFMS.

Design and performance of a desktop time-of-flight mass spectrometer for analyzing metal ions

We have described a home-made desktop orthogonal-injection time-of-flight (O-ToF) mass spectrometer combining a collisional cooling system. This O-ToF consists of a simple electrospray ion source, an atmosphere-vacuum interface, an area of transmission, including a radio-frequency only quadrupole (RF- only quadrupole, RFQ) as a collisional cooling cell and an orthogonal ToF mass analyzer. In order to detect ions of small m/z value, such as small metal ions, the RFQ has been improved to weaken the mass discrimination effect against low mass ions. Metal salt solutions were used in the experiment. The system has shown a satisfactory resolving power in the spectra (m/Δm = 3500), a good mass stability, a limit of detection of 80 fg and a mass accuracy of 48 ppm. The dynamic range is found to be from 10(-8) mol L(-1) to 10(-5) mol L(-1), allowing the semi-quantitative analysis of metal ions.

Development of a stigmatic mass microscope using laser desorption∕ionization and a multi-turn time-of-flight mass spectrometer

A novel stigmatic mass microscope using laser desorption∕ionization and a multi-turn time-of-flight mass spectrometer, MULTUM-IMG, has been developed. Stigmatic ion images of crystal violet masked by a fine square mesh grid with a 12.7 μm pitch as well as microdot patterns with a 5 μm dot diameter and a 10 μm pitch made with rhodamine B were clearly observed. The estimated spatial resolution was about 3 μm in the linear mode with a 20-fold ion optical magnification. Separating stigmatic ion images according to the time-of-flight, i.e., the mass-to-charge ratio of the ions was successfully demonstrated by a microdot pattern made with two different dyes, crystal violet and methylene blue. Stigmatic ion images of a microdot pattern made with crystal violet were observed after circulation in MULTUM-IMG, and the pattern of the ion image was maintained after ten cycles in MULTUM-IMG. A section of a mouse brain stained with crystal violet and methylene blue was observed in the linear mode, and the stigmatic total ion image of crystal violet and methylene blue agreed well with the optical microphotograph of the hippocampus for the same section.

Development of multi-turn time-of-flight mass spectrometers and their applications

The mass resolution of a time-of-flight (ToF) mass spectrometer is directly proportional to its total flight path length. We have developed multi-turn ToF mass spectrometers, where ions are stored in a fixed orbit within electrostatic sectors and allowed to propagate the said orbit numerous times. With each successive orbit, the flight path is correspondingly increasing. The first multi-turn ToF mass spectrometer, the MULTUM Linear plus, was developed for cometary exploration. The spectrometer consists of four cylindrical electrostatic sectors and 28 electrostatic quadrupole lenses. The size of the analyzer is 40 cm square. Mass resolution is demonstrated to increase according to the number of ion cycles. A mass resolution of greater than 350,000 was achieved after 501.5 cycles. Another multi-turn ToF mass spectrometer, the MULTUM II, which consists of only four toroidal electrostatic sectors, was also developed in an effort to reduce the number of quadrupole lenses. We are developing various types of mass spectrometer based on the MULTUM II technology, a ToF/ToF mass spectrometer "MULTUM- TOF/TOF", a stigmatic imaging mass spectrometer "MULTUM-IMG" and miniature mass spectrometers of high mass resolving power, the "MULTUM-S" series.

Design of a new multi-turn ion optical system 'IRIS' for a time-of-flight mass spectrometer

A new multi-turn ion optical system 'IRIS' has been designed for use with a high-performance time-of-flight (TOF) mass spectrometer, which satisfies the new design concepts of time focusing and phase space stability. It has an elliptical flight path composed of four toroidal electric sectors, with a flight path length for one lap of 0.974 m. Dimensions and voltages of sector electrodes have been optimized to satisfy theoretical requirements by simulations using surface charge method. Generally, multi-turn instruments require an injection and ejection system to inject and eject ions. On the basis of this ion optical study, we have designed an injection and ejection ion optical system, which achieves time focusing for the total system. Furthermore, we have designed novel field-adjusting electrodes (FAEs) for the perforated sectors in the injection and ejection systems, which accurately correct the electric potential around the perforated sector's hole. We have also used simulations to evaluate mass resolving power and ion transmissions for various lap numbers or flight path lengths. Through these we have confirmed that mass resolving powers of over 100,000 can be achieved with reasonable ion transmissions for a given set of initial conditions. Usually a multi-turn TOF mass spectrometer with a closed optic axis has mass range limitations from overtaking ions. To solve this problem, a TOF segmentation method is proposed that identifies all peaks in a TOF spectrum, including those from overtaking ions.

Development of an ion trap/multi-turn time-of-flight mass spectrometer with potential- lift

An ion trap/multi-turn time-of-flight (ToF) mass spectrometer with potential-lift has been developed. This system consists of an external ion source, a lens system, an ion trap, a potential-lift, a multi-turn ToF mass spectrometer and a detector. The ion trap consists of hyperbolic electrode cross-sections (Paul trap) and is used as an ion storage device. The potential-lift, which is part of the flight tube, was attached between the ion trap and the multi-turn ToF mass spectrometer. The potential-lift is known to be useful for increasing the kinetic energy of the ions. In order to check the ability of the potential-lift, mass distributions of [(CsI)(n) Cs]+ clusters (n = 1-9) were measured. The relative intensity ratios of the [(CsI)(n)Cs]+ clusters were consistent with the results obtained using other apparatus. To check the properties of the new apparatus, Xe+ isotopes were analyzed using either a linear or multi-turn ToF mass spectrometer. In the linear mode, the mass resolution was 500. In the multi-turn mode, the resolution depended on the number of cycles of the multi-turn ToF mass spectrometer; the mass resolution was 4400 (FWHM) after nine cycles. This new apparatus with a high resolution will be useful for measurements of ion-molecule reactions and photodissociations.

Comparison of mass spectra of peptides in different matrices using matrix-assisted laser desorption/ionization and a multi-turn time-of-flight mass spectrometer, MULTUM-IMG

The mass spectra of peptides obtained with different matrices were compared using a matrix-assisted laser desorption/ionization (MALDI) ion source and a multi-turn time-of-flight (TOF) mass spectrometer, MULTUM-IMG, which has been developed at Osaka University. Two types of solid matrices, alpha-cyano-4-hydroxycinnamic acid (CHCA) and 2,5-dihydroxybenzoic acid (DHB), and a liquid matrix made from a mixture of 3-aminoquinoline and CHCA were used. When measuring the peak signal intensity of human angiotensin II [M+H]+ from a fixed sample position, the liquid matrix produced a stable signal over 1000 laser shots, while the signal obtained with CHCA and DHB decayed after about 300 and 100 shots, respectively. Significant differences in the mass resolving power were not observed between the spectra obtained with the three matrices. Signal peak areas were measured as a function of the cycle number in a multi-turn ion trajectory, i.e., the total flight time over a millisecond time scale. For both [M+H]+ of human angiotensin II and bovine insulin, the decay of the signal peak area was the most significant with CHCA, while that measured with DHB was the smallest. The results of the mean initial ion velocity measurements suggested that the extent of metastable decomposition of the analyte ions increased in order of DHB, the liquid matrix, and CHCA, which is consistent with the difference in the decay of the signal peak area as the total flight time increased.

High-resolution mass spectrometers

Over the past decade, mass spectrometry has been revolutionized by access to instruments of increasingly high mass-resolving power. For small molecules up to approximately 400 Da (e.g., drugs, metabolites, and various natural organic mixtures ranging from foods to petroleum), it is possible to determine elemental compositions (C(c)H(h)N(n)O(o)S(s)P(p)...) of thousands of chemical components simultaneously from accurate mass measurements (the same can be done up to 1000 Da if additional information is included). At higher mass, it becomes possible to identify proteins (including posttranslational modifications) from proteolytic peptides, as well as lipids, glycoconjugates, and other biological components. At even higher mass ( approximately 100,000 Da or higher), it is possible to characterize posttranslational modifications of intact proteins and to map the binding surfaces of large biomolecule complexes. Here we review the principles and techniques of the highest-resolution analytical mass spectrometers (time-of-flight and Fourier transform ion cyclotron resonance and orbitrap mass analyzers) and describe some representative high-resolution applications.

High-energy collision induced dissociation fragmentation pathways of peptides, probed using a multiturn tandem time-of-flight mass spectrometer "MULTUM-TOF/TOF"

A new multiturn tandem time-of-flight (TOF) mass spectrometer "MULTUM-TOF/TOF" has been designed and constructed. It consists of a matrix-assisted laser desorption/ionization ion source, a multiturn TOF mass spectrometer, a collision cell, and a quadratic-field ion mirror. The multiturn TOF mass spectrometer can overcome the problem of precursor ion selection in TOF, due to insufficient time separation between two adjacent TOF peaks, by increasing the number of cycles. As a result, the total TOF increases with the increase in resolving power. The quadratic-field ion mirror allows temporal focusing for fragment ions with different kinetic energies. Product ion spectra from monoisotopically selected precursor ions of angiotensin I, substance P, and bradykinin have been obtained. The fragment ions observed are mainly the result of high-energy collision induced dissociation.

The design and characteristic features of a new time-of-flight mass spectrometer with a spiral ion trajectory

A new time-of-flight (TOF) mass spectrometer with a corkscrew ion trajectory was designed and constructed. The spiral trajectory was realized by using four toroidal electrostatic sectors. Each had fifteen-stories made of sixteen Matsuda plates piled up inside a cylindrical electrostatic sector. The ions passed the four toroidal electrostatic sectors sequentially and revolved along a figure-eight-shaped orbit on a certain projection plane. During the multiple revolutions, each ion trajectory was shifted by 50 mm per cycle on a direction perpendicular to the projection plane, thus generating a spiral trajectory. The flight path length of one cycle was 1.308 m so that the maximum flight path length became approximately 20 m. The mass resolution, mass accuracy, and ion transmission were tested by utilizing an orthogonally coupled electron ionization source. A mass resolution of 35,000 (FWHM) for m/z greater than 300 was achieved. Even in a lower mass region, mass resolutions of more than 20,000 (FWHM) were confirmed with a doublet of (12)C(5)(1)H(5)(14)N(+) and (13)C(12)C(5)(1)H(6)(+). The mass accuracy was also improved such that it was better than 1 ppm with only one internal standard peak. An ion transmission of approximately of 100% was observed for 15 cycles.

High-resolution time-of-flight spectra obtained using the MULTUM II multi-turn type time-of-flight mass spectrometer with an electron ionization ion source

This paper describes experiments demonstrating the high mass-resolving power of the MULTUM II multi-turn type time-of-flight (ToF) mass spectrometer with a 1.308-meter circuit controlled by four toroidal electric sector fields(1) and an electron ionization (EI) ion source. A mass resolution of 250,000 [full-width at half maximum: (FWHM)] was obtained for N(2)(+) after a flight time of 9.0 ms (flight cycles: 1,200, flight length: 1,500 M). A doublet of (12)C(5)H(5)(14)N and (13)C(12)C(5)H(6) (m/Deltam = 9,746; Deltam: mass difference of doublet, m: mass of lighter ion of doublet) was separated and a mass resolution of 91,000 (FWHM) was obtained. A doublet of CDCl(2) and CH(2)Cl(2) (m/Deltam = 54,162) was also separated. A mass resolution of 115,000 (FWHM) was then achieved. When one peak of these doublets was used as a calibrant, the mass of the other peak was determined within a few ppm by mass difference. The ToF depending on the square of m/z was significantly larger than the systematic errors in the ToF, so that good mass accuracy was obtained by one-point mass determination.