Orthogonal Acceleration Research Articles

Combining Enhanced Resolving Power with Duty Cycle Improvements on a Multi-Reflecting Time-of-Flight Mass Spectrometer.

The combination of enhanced resolving power and improved duty cycle on a multireflecting time-of-flight mass spectrometer is described. Resolving power increases are achieved by extending the effective ion path length from 47 m to greater than 200 m. Path length increases are achieved through containment of ions within the analyzer for up to N = 5 passes using a pulsed deflection electrode. Resolving power was shown to increase from 220,000 to 402,000 (fwhm) at m/z 785 for N = 1 and N = 4 analyzer passes, respectively. Due to the timing of the pulsed deflection electrode, the approach is particularly suited to high resolution analysis over a targeted m/z range. Duty cycle enhancements are achieved for ions of the targeted m/z range via accumulation prior to orthogonal acceleration, providing signal improvements of 2 orders of magnitude. Achieving such high resolving powers at fast scan rates (30 Hz) can yield additional information such as fine isotope structure; when combined with ppb mass measurement accuracy, high confidence in analyte identification can be achieved. The technique is applied for N = 2 analyzer passes, demonstrating fine isotope structure for a typical UHPLC metabolite identification experiment at a 10 Hz acquisition rate. Additionally, mass spectrometry imaging data is acquired using DESI, demonstrating the improved image clarity achieved at >300,000 (fwhm).

Influence of polarity mode switching and standby times on signal stability and detection of aspirated droplet signatures in electrospray mass spectrometry

Electrospray ionization plays a central role in modern analytical chemistry. It is often used in combination with an HPLC system and is able to transfer large molecules, such as proteins and complexes, into the gas phase. A liquid solution containing the analyte is sprayed in a strong electric field. Charged droplets generated by this process release the analyte molecules which can ultimately be analyzed by the mass spectrometer system. However, the exact mechanisms of droplet generation and ion release are still not fully understood and are under investigation. Recent literature puts the focus on droplet disintegration and shows that the analyte ions are not exclusively released from the droplets within the ionization chamber but rather in the whole mass spectrometer system. Previous experiments allow the direct observation of the signatures of fragmented droplets within the analyzer region of a time-of-flight mass spectrometer: An oscilloscope was connected to a secondary electron multiplier which serves as an auxiliary ion detector, located downstream of the orthogonal acceleration stage of a time-of-flight mass spectrometer. The oscilloscope is thus able to monitor the time-resolved ion current in the mass analyzer region. Pulses of extraordinarily high ion currents are observable here which are attributed to aspirated charged droplets.This work provides insights into long-term experiments with this experimental setup. There is a focus on signal stability, in the presence of such droplet signatures. It is apparent that the standby time of the instrument between individual measurements and the time since a switch of the polarity mode, has a significant influence on the signal stability. There are also indications that the observations of droplet signatures and the MS signal stability are correlated.

Observation of Large, Charged Droplet Signatures within the High-Vacuum Region of a Commercial Electrospray TOF-MS.

Electrospray ionization (ESI) is one of the most prominent atmospheric pressure ionization techniques in modern mass spectrometry. It generates charged droplets from an analyte-containing solution as an initial step in the ionization process. Textbooks and the majority of the articles assume the entire droplet evaporation and release of bare analyte ions within the ionization chamber. However, non-mass-spectrometry-related literature and recent reports demonstrate droplet observation in regions of the vacuum systems of a variety of mass spectrometers. In this work, we report on the observation of large droplet fragments within the orthogonal acceleration stage of a Bruker micrOTOF by connecting an oscilloscope to an auxiliary ion current detector downstream of the acceleration stage. Moreover, we detected fragment debris even with the MCP TOF detector by evaluating individual TOF spectra. Droplet fragments appear as pronounced and intensive pulses of the ion current. This observation is clearly connected to ESI, as other atmospheric pressure ionization methods do not show this behavior. The recorded droplet signatures show clear dependencies on the ion source and transfer stage parameters. The existence of large and highly charged droplets may adversely affect or at least impact the analytical performance of the instrument due to space charge or complex heterogeneous chemical reactions. Furthermore, the penetration of large charged aggregates into the vacuum system explains the reported surface contamination after multipole stages. This contamination of critical components leads to substantially higher maintenance efforts.

Improvement of methods of interception of enemy UAVs

The main result of this work is the creation of a methodology for determining the coordinates, velocities and trajectories of spatial movements of moving objects by means of kinematic design and the development of principle schemes for the optimal placement of radar search equipment for the successful detection of enemy UAVs. Its purpose is to increase the defense capability of military units, populated areas of Ukraine and their infrastructure by resisting attacks by attack and sabotage reconnaissance unmanned aerial vehicles (UAVs). The protection scheme is based on the determination of coordinates, movement speeds and trajectories of spatial movements of enemy aircraft by means of kinematic design. The established coordinates of enemy UAVs are reported to command posts equipped with liquidator drones (kamikaze) and small arms or to control points of anti-aircraft missile systems (SAMS), which eliminate these aircraft. The proposed improvement of the widespread method of radar search for moving objects is based on the introduction of additional search radar equipment and mathematical apparatus for precise calculations of coordinates and parameters of spatial movements of moving objects by means of kinematic design. Two paired radar search systems, equipped with modern high-speed computing equipment with appropriate software, are able to "screen out" false return electromagnetic signals. This makes it possible to clearly single out the wanted moving object and subsequently track its movement in space. Corresponding mathematical dependencies are proposed for calculating the distance of a moving object to radar stations, its coordinates in the introduced orthogonal coordinate system, speed and acceleration of movement, that is, instantaneous coordinates and parameters of spatial movements of moving objects. This makes it possible to increase the effectiveness of detecting enemy attack and sabotage-reconnaissance unmanned aerial vehicles, including Iranian-made drones of the Sahed-136 model.

Evaluation of acquisition modes for semi-quantitative analysis by targeted and untargeted mass spectrometry.

RationaleAnalyte quantitation by mass spectrometry underpins a diverse range of scientific endeavors. The fast‐growing field of mass spectrometer development has resulted in several targeted and untargeted acquisition modes suitable for these applications. By characterizing the acquisition methods available on an ion mobility (IM)‐enabled orthogonal acceleration time‐of‐flight (oa‐ToF) instrument, the optimum modes for analyte semi‐quantitation can be deduced.MethodsSerial dilutions of commercial metabolite, peptide, or cross‐linked peptide analytes were prepared in matrices of human urine or Escherichia coli digest. Each analyte dilution was introduced into an IM separation‐enabled oa‐ToF mass spectrometer by reversed‐phase liquid chromatography and electrospray ionization. Data were acquired for each sample in duplicate using nine different acquisition modes, including four IM‐enabled acquisitions modes, available on the mass spectrometer.ResultsFive (metabolite) or seven (peptide/cross‐linked peptide) point calibration curves were prepared for analytes across each of the acquisition modes. A nonlinear response was observed at high concentrations for some modes, attributed to saturation effects. Two correction methods, one MS1 isotope‐correction and one MS2 ion intensity‐correction, were applied to address this observation, resulting in an up to twofold increase in dynamic range. By averaging the semi‐quantitative results across analyte classes, two parameters, linear dynamic range (LDR) and lower limit of quantification (LLOQ), were determined to evaluate each mode.ConclusionA comparison of the acquisition modes revealed that data‐independent acquisition and parallel reaction monitoring methods are most robust for semi‐quantitation when considering achievable LDR and LLOQ. IM‐enabled modes exhibited sensitivity increases, but a simultaneous reduction in dynamic range required correction methods to recover. These findings will assist users in identifying the optimum acquisition mode for their analyte quantitation needs, supporting a diverse range of applications and providing guidance for future acquisition mode developments.

Simultaneous on-line vacuum single- and multi-photon ionization on an orthogonal acceleration time-of-flight mass spectrometer platform.

The development of orthogonal acceleration time-of-flight (oa-tof) technology is driven forward due to higher mass accuracy and resolving power than conventional linear/reflectron tof instruments. This is achieved with a more accurate definition of starting energies and coordinates of ions by spatial separation of ion generation and orthogonal ion extraction. Consequently, the ability to cover the whole mass spectral range without scanning is not given anymore. Therefore, continuous ion sources are favored for ensuring high duty cycles and thus high temporal resolution. For pulsed ion sources, high repetition rates are mandatory for covering large m/z ranges without losing their high temporal resolution. We have combined an oa-tof with deuterium lamp single-photon ionization (SPI) as a continuous ion source together with a pulsed 2000 Hz excimer (KrF) laser for resonance enhanced multi-photon ionization (REMPI). These two ionization techniques can be used simultaneously. To the best of our knowledge, this system is the first of its kind in combining a vacuum pulsed ionization source with an oa-tof instrument without any other ion storage hardware. The combination of a soft broadband ionization for organics (SPI) in combination with a very sensitive and selective soft ionization (REMPI) can be used for covering the whole mass range or in targeted on-line monitoring cases one or several smaller mass ranges. To demonstrate the simultaneous SPI/REMPI-oa-tof technique, two applicative areas are explored: on-line monitoring of coffee roast gas emissions and e-cigarette vapor. The complementary information from SPI and REMPI signals are combined in a way to exploit the advantages of both ionization types. In a further development step, a second data acquisition card is built into the system. This modification allows the independent storage of data from both ionization methods without mixing. For demonstration, a third example with a GC measurement is provided. The last example shows the possibility of modified sensitivities for different mass regions in REMPI data acquisition without affecting the SPI channel. The newly developed system shows high robustness in terms of measurements in real industrial environments. The simultaneous measurement technique provides a higher density of information in a single measurement, saving time and resources.

A New Pathway for Intersystem Crossing: Unexpected Products in the O(3P) + Cyclopentene Reaction.

We investigated the reaction of O(3P) with cyclopentene at 4 Torr and 298 K using time-resolved multiplexed photoionization mass spectrometry, where O(3P) radicals were generated by 351 nm photolysis of NO2 and reacted with excess cyclopentene in He under pseudo-first-order conditions. The resulting products were sampled, ionized, and detected by tunable synchrotron vacuum ultraviolet radiation and an orthogonal acceleration time-of-flight mass spectrometer. This technique enabled measurement of both mass spectra and photoionization spectra as functions of time following the initiation of the reaction. We observe propylketene (41%), acrolein + ethene (37%), 1-butene + CO (19%), and cyclopentene oxide (3%), of which the propylketene pathway was previously unidentified experimentally and theoretically. The automatically explored reactive potential energy landscape at the CCSD(T)-F12a/cc-pVTZ//ωB97X-D/6-311++G(d,p) level and the related master equation calculations predict that cyclopentene oxide is formed on the singlet potential energy surface, whereas propylketene is first formed on the triplet surface. These calculations provide evidence that significant intersystem crossing can happen in this reaction not only around the geometry of the initial triplet adduct but also around that of triplet propylketene. The formation of 1-butene + CO is initiated on the triplet surface, with bond cleavage and hydrogen transfer occurring during intersystem crossing to the singlet surface. At present, we are unable to explain the mechanistic origins of the acrolein + ethene channel, and we thus refrain from assigning singlet or triplet reactivity to this channel. Overall, at least 60% of the products result from triplet reactivity. We propose that the reactivity of cyclic alkenes with O(3P) is influenced by their greater effective degree of unsaturation compared with acyclic alkenes. This work also suggests that searches for minimum-energy crossing points that connect triplet surfaces to singlet surfaces should extend beyond the initial adducts.

A convolution approach to calculating the m/z-dependent mass analyzer response in orthogonal acceleration time-of-flight mass spectrometers

A novel computational method is developed to calculate the mass bias of orthogonal acceleration time-of-flight mass spectrometers (OA-TOFMS) by evaluating the m/z-dependent transmission efficiency with which ions strike the surface of the detector and the m/z-dependent ion sampling efficiency with which ions are selected for mass analysis. The theory considers the initial ion energy distribution of the primary ion beam and utilizes mathematical convolution to establish the subsequent trajectory of all ions extracted into the OA-TOFMS. By considering the energy-dependent transmission of ions and the ion sampling efficiency together, the resultant mass bias is estimated. The mathematical description is developed for OA-TOFMS using different ionization sources and ion energy distributions, and several examples covering possible time-of-flight conditions and aspects of their application are considered.

Control of time front tilts in planar multi-reflection time-of-flight mass analyzers by local wedge fields

It is shown that an electrostatic field structure including a local wedge field in the area of small ion kinetic energies, followed by a planar accelerating field, allows to efficiently vary and control the inclination angle of time fronts (isochronous surfaces) in essentially parallel ion beams. When combined with deflectors, wedge fields allow independent control of the trajectory inclination angle and of the time front inclination angle. Two particular applications of local wedge fields are shown for improvement of planar multi-reflecting time-of-flight (MR-TOF) analyzers. One is a combination of an orthogonal accelerator and a deflector arranged for dense folding of ion trajectories. The other is a combination of an ion mirror and a deflector for reversing the ion motion and elongation of the flight paths.

From the discovery of field ionization to field desorption and liquid injection field desorption/ionization-mass spectrometry-A journey from principles and applications to a glimpse into the future.

The discovery of the ionizing effect of strong electric fields in the order of volts per Ångstrom in the early 1950s eventually led to the development of field ionization-mass spectrometry (FI-MS). Due to the very low ion currents, and thus, limited by the instrumentation of the 1960s, it took some time for the, by then, new technique to become adopted for analytical applications. In FI-MS, volatile or at least vaporizable samples mainly deliver molecular ions, and consequently, mass spectra showing no or at least minor numbers of fragment ion signals. The next major breakthrough was achieved by overcoming the need to evaporate the analyte prior to ionization. This was accomplished in the early 1970s by simply depositing the samples onto the field emitter and led to field desorption-mass spectrometry (FD-MS). With FD-MS, a desorption ionization method had become available that paved the road to the mass spectral analysis of larger molecules of low to high polarity and even of organic salts. In FD-MS, all of these analytes deliver spectra with no or at least few fragment ion peaks. The last milestone was the development of liquid injection field desorption/ionization (LIFDI) in the early 2000s that allows for sample deposition under the exclusion of atmospheric oxygen and water. In addition to sampling under inert conditions, LIFDI also enables more robust and quicker operation than classical FI-MS and FD-MS procedures. The development and applications of FI, FD, and LIFDI had mutual interference with the mass analyzers that were used in combination with these methods. Vice versa, the demand for using these techniques on other than magnetic sector instruments has effectuated their adaptation to different types of modern mass analyzers. The journey started with magnetic sector instruments, almost skipped quadrupole analyzers, encompassed Fourier transform ion cyclotron resonance (FT-ICR) and orthogonal acceleration time-of-flight (oaTOF) analyzers, and finally arrived at Orbitraps. Even interfaces for continuous-flow LIFDI have been realized. Even though being niche techniques to some degree, one may be confident that FI, FD, and LIFDI have a promising future ahead of them. This Account takes you on the journey from principles and applications of the title methods to a glimpse into the future.

Detection of Chemical Compositions of Ultrafine Nanoparticles by a Vacuum Ultraviolet Photoionization Nucleation Aerosol Mass Spectrometer

Abstract A vacuum ultraviolet photoionization nucleation aerosol mass spectrometer (VUVPI-AMS) was developed for detection of chemical compositions of ultrafine nanoparticles with size of less than 100 nm. A commercial nano-scanning mobility particle sizer (Nano-SMPS) was employed for size-selection of ultrafine nanoparticles, as well as the size distribution was measured. A special aerodynamic lens was designed to transfer and focus the ultrafine nanoparticles into the vacuum. On arriving on the hot surface of the heater, the ultrafine nanoparticles were vaporized and changed into gas-phase molecules, which were then softly photoionized at their ionization energy thresholds by the VUV photons emitted from a commercial 10.6 eV krypton discharge lamp. A home-made orthogonal acceleration reflectron time-of-flight mass analyzer was adopted to measure the mass of ions. As representative examples, the dioctyl phthalate (DOP) ultrafine nanoparticles and the nucleation nanoparticles from the ozonolysis reaction of α-pinene were measured and their chemical compositions were obtained with molecular information.

Atmospheric Pressure Chemical Ionisation study of selected Volatile Organic Compounds (VOCs) by Ion Mobility Spectrometry coupled with orthogonal acceleration Time Of Flight Mass Spectrometry

In this work, we present an Atmospheric Pressure Chemical Ionisation (APCI) study of several organic solvents relevant to Thin Layer Chromatography (TLC) (methanol, ethanol, propan-2-ol, acetone, ethyl acetate, diethylamine). The solvents were investigated using an Ion Mobility Spectrometry (IMS) combined with orthogonal acceleration Time Of Flight Mass Spectrometry (IMS-oaTOF MS). The solvents were iononised by Reactant Ions (RI – H+.(H2O)3,4 m/z 55 and 73). The ions were analysed using IMS and IMS-oaTOF technique was used to assign the ion mobility peaks to ions according to their m/z. IMS spectra of methanol, ethanol, propan-2-ol and diethylamine exhibited only one peak (reduced ion mobilities of 2.19, 2.07, 1.98, 2.06 cm2s−1V−1 respectively) whereas acetone and ethyl acetate were characterised by two peaks (2.15, 1.85 and 1.94, 1.53 cm2s−1V−1 respectively). The IMS-oaTOF spectrometry assigned IMS peaks of VOCs to M⋅H+(H2O)n. n = 0,1,2 or M2⋅H+ ions, where M represents the solvent molecule.

Fast quantification of whisky lactone in oak wood by ion mobility spectrometer

An Ion Mobility Spectrometry (IMS) apparatus has been used to detect the β-methyl-γ-octalactone (Whisky Lactone – WL) standard in the air and as well WL vapours originating from the oak wood samples. The IMS was equipped with Atmospheric Pressure Chemical Ionisation (APCI) ion source based on a Corona Discharge (CD) and was operated in the positive polarity. The IMS spectrum of WL exhibits two peaks, a monomer with reduced ion mobility value K0 = 1.39 cm2V−1s−1 and dimer K0 = 1.09 cm2V−1s−1. Using Ion Mobility orthogonal acceleration Time of Flight mass spectrometer (IMS-oaTOF MS) these peaks were identified as protonated monomer M.H+.(H2O)0,1 and dimer M2.H+ ions respectively. The limit of detection study resulted in LOD for WL of 50 ppbv. Detection of WL from oak wood samples of different “Quality Level” (QL) categories (categories 1 to 10), indicated strong correlation between the QL category number and the response of the IMS.

An Analytical Perspective on Protein Analysis and Discovery Proteomics by Ion Mobility-Mass Spectrometry.

Ion mobility combined with mass spectrometry (IM-MS) is a powerful technique for the analysis of biomolecules and complex mixtures. This chapter reviews the current state-of-the-art in ion mobility technology and its application to biology, protein analysis, and quantitative discovery proteomics in particular, from an analytical perspective. IM-MS can be used as a technique to separate mixtures, to determine structural information (rotationally averaged cross-sectional area) and to enhance MS duty cycle and sensitivity. Moreover, IM-MS is ideally suited for hyphenating with liquid chromatography, or other front-end separation techniques such as, GC, microcolumn LC, capillary electrophoresis, and direct analysis, including MALDI and DESI, providing an semiorthogonal layer of separation, which affords the more unambiguous and confident detection of a wide range of analytes. To illustrate these enhancements, as well as recent developments, the principle of in-line IM separation and hyphenation to orthogonal acceleration time-of-flight mass spectrometers are discussed, in addition to the enhancement of biophysical MS-based analysis using typical proteomics and related application examples.

A comparison of collision cross section values obtained via travelling wave ion mobility-mass spectrometry and ultra high performance liquid chromatography-ion mobility-mass spectrometry: Application to the characterisation of metabolites in rat urine

A comprehensive Collision Cross Section (CCS) library was obtained via Travelling Wave Ion Guide mobility measurements through direct infusion (DI). The library consists of CCS and Mass Spectral (MS) data in negative and positive ElectroSpray Ionisation (ESI) mode for 463 and 479 endogenous metabolites, respectively. For both ionisation modes combined, TWCCSN2 data were obtained for 542 non-redundant metabolites. These data were acquired on two different ion mobility enabled orthogonal acceleration QToF MS systems in two different laboratories, with the majority of the resulting TWCCSN2 values (from detected compounds) found to be within 1% of one another. Validation of these results against two independent, external TWCCSN2 data sources and predicted TWCCSN2 values indicated to be within 1–2% of these other values. The same metabolites were then analysed using a rapid reversed-phase ultra (high) performance liquid chromatographic (U(H)PLC) separation combined with IM and MS (IM-MS) thus providing retention time (tr), m/z and TWCCSN2 values (with the latter compared with the DI-IM-MS data). Analytes for which TWCCSN2 values were obtained by U(H)PLC-IM-MS showed good agreement with the results obtained from DI-IM-MS. The repeatability of the TWCCSN2 values obtained for these metabolites on the different ion mobility QToF systems, using either DI or LC, encouraged the further evaluation of the U(H)PLC-IM-MS approach via the analysis of samples of rat urine, from control and methotrexate-treated animals, in order to assess the potential of the approach for metabolite identification and profiling in metabolic phenotyping studies. Based on the database derived from the standards 63 metabolites were identified in rat urine, using positive ESI, based on the combination of tr, TWCCSN2 and MS data.

Fault Identification Method of Diesel Engine in Light of Pearson Correlation Coefficient Diagram and Orthogonal Vibration Signals

In order to select fault feature parameters simply and quickly and improve the identification rate of diesel engine faults by using the vibration signals, this paper proposes a diesel engine fault identification method on the basis of the Pearson correlation coefficient diagram (PCC Diagram) and the orthogonal vibration signals. At first, the orthogonal vibration acceleration signals are synchronously acquired in the direction of the top and side of the cylinder head. And the time-domain feature parameters are extracted from the orthogonal vibration acceleration signals to obtain the Pearson correlation coefficient (PCC). Then, the correlation coefficient diagram used to do feature parameter screening is constructed by selecting the feature parameters with the correlation coefficient of more than 0.9. Finally, generalized regression neural network (GRNN) is adopted to classify and identify fuel supply fault in diesel engine. The results show that using the PCC Diagram can simplify the selection process of the feature parameters of the orthogonal vibration signals quickly and effectively. It can also improve the fault identification rate of diesel engine significantly with the help of adding the newly proposed cross-correlation coefficient of the orthogonal vibration signals into the GRNN input feature vector set.

Product Detection of the CH Radical Reactions with Ammonia and Methyl-Substituted Amines.

Reactions of the methylidyne (CH) radical with ammonia (NH3), methylamine (CH3NH2), dimethylamine ((CH3)2NH), and trimethylamine ((CH3)3N) have been investigated under multiple collision conditions at 373 K and 4 Torr. The reaction products are detected by using soft photoionization coupled to orthogonal acceleration time-of-flight mass spectrometry at the Advanced Light Source (ALS) synchrotron. Kinetic traces are employed to discriminate between CH reaction products and products from secondary or slower reactions. Branching ratios for isomers produced at a given mass and formed by a single reaction are obtained by fitting the observed photoionization spectra to linear combinations of pure compound spectra. The reaction of the CH radical with ammonia is found to form mainly imine, HN═CH2, in line with an addition-elimination mechanism. The singly methyl-substituted imine is detected for the CH reactions with methylamine, dimethylamine, and trimethylamine. Dimethylimine isomers are formed by the reaction of CH with dimethylamine, while trimethylimine is formed by the CH reaction with trimethylamine. Overall, the temporal profiles of the products are not consistent with the formation of aminocarbene products in the reaction flow tube. In the case of the reactions with methylamine and dimethylamine, product formation is assigned to an addition-elimination mechanism similar to that proposed for the CH reaction with ammonia. However, this mechanism cannot explain the products detected by the reaction with trimethylamine. A C-H insertion pathway may become more probable as the number of methyl groups increases.

Chatter detection based on wavelet coherence functions in micro-end-milling processes

Micro-end-milling is used for the fabrication of complex geometrical features with high precision on a wide variety of materials. One of the main challenges is related to chatter vibrations, which are detrimental to the productivity and overall quality of the manufactured parts. In this article, a novel chatter-detection method based on wavelet coherence functions is proposed to evaluate the stability of the micro-end-milling process. Then, the method is experimentally tested under different cutting conditions. The results show that the wavelet coherence functions of two orthogonal acceleration signals are sensitive enough and applicable for chatter detection. When chatter occurs, the two orthogonal acceleration signals are highly correlated at the chatter frequency, resulting in a sharp increase in the magnitude of the wavelet coherence functions to values approaching unity.

Computing the Parameters of an Orthogonal Accelerator Based on a Wedge-Shaped Electrostatic Mirror with a 2D Field

A wedge-shaped mirror with a two-dimensional field, used as an orthogonal ion accelerator and a time-of-flight mass spectrometer, is considered. A nonuniform electric field is generated in the mirror by varying the potentials on its boundary electrodes without electrostatic grids. An ion bunch extracted from the source is accelerated by a field pulse in the mirror, and its size along the direction of motion is considerably reduced. The characteristics of the proposed time-of-flight spectrometer are obtained via a Monte Carlo simulation, allowing for the thermal spread of ion velocities.

Development of an ion guide device in orthogonal acceleration time-of-flight mass spectrometer coupled with laser resonance ionization source

Laser-resonance-ionization time-of-flight mass spectrometer (LRI-TOF-MS) has been widely used in the analysis of trace isotopes because of its advantages such as high isotope selectivity, high sensitivity, and capability to receive all isotopes in a single measurement. A LRI-TOF-MS was built in our laboratory to search for efficient laser resonance ionization scheme of some elements and analyse their isotopic composition. To improve the resolution and suppress the peak tail, the orthogonal-acceleration technology was used in LRI-TOF-MS for the first time, and the design method of electrical parameters of TOF mass analyser with dual-stage reflectrons was derived. The developed ion guide device consisted of several different electrostatic lenses and was manufactured through theoretical analysis, SIMION simulation and experimental evaluation. The results show that the LRI source and the TOF mass analyser matched well in performance.