Commercial Mass Spectrometer Research Articles

Dueling electrospray implemented on a traveling-wave ion mobility/time-of-flight mass spectrometer: Towards a gas-phase workbench for structural biology

The traveling wave trap cell of a commercial ion mobility mass spectrometer (IM/MS) was used as a gas-phase reactor for covalent chemistry by making a simple modification to a standard nanoelectrospray source. Reagents and analytes were generated from pulsed opposite polarity nanoelectrospray sources and isolated by their m/z prior to reaction. Covalent bond formation was first observed with the model peptide angiotensin I. The modification site was identified as the N-terminus of the peptide by collision induced dissociation (CID). The IM cell separated the covalent reaction product from the proton transfer product by their respective ion mobilities. Next, the effects of several trapping parameters, including the trap traveling wave height, the trap RF voltage, and the trap pressure, were evaluated. Decreasing traveling wave height and increasing RF voltage and pressure increased the number of proton transfer events from apomyoglobin to reagent anions. The 6+ charge state of ubiquitin generated from nanospray under native-like conditions was covalently modified in the gas phase through ion/ion reactions. Probing the reacted protein with CID led to the assignment of lysine 29 and arginine 54 as reactive nucleophiles accessible to the reagent. IM analysis of the unmodified native-like 6+ charge state revealed that the gas-phase structure of the protein in the trap was in its compact form. Overall, we introduce a promising method for three-dimensional structural characterization of biomacromolecules.

Development of a robotics platform for automated multi-ionization mass spectrometry.

Successful coupling of a multi-ionization automated platform with commercially available mass spectrometers provides improved coverage of compounds in complex mixtures through implementation of new and traditional ionization methods. The versatility of the automated platform is demonstrated through coupling with mass spectrometers from two different vendors. Standards and complex biological samples were acquired using electrospray ionization (ESI), solvent-assisted ionization (SAI) and matrix-assisted ionization (MAI). The MS™ prototype automated platform samples from 96- or 384-well plates as well as surfaces. The platform interfaces with Thermo Fisher Scientific mass spectrometers by replacement of the IonMax source, and on Waters mass spectrometers with additional minor source inlet modifications. The sample is transferred to the ionization region using a fused-silica or metal capillary which is cleaned between acquisitions using solvents. For ESI and SAI, typically 1 μL of sample solution is drawn into the capillary tube and for ESI slowly dispensed near the inlet of the mass spectrometer with voltage placed on the delivering syringe barrel to which the tubing is attached, while for SAI the sample delivery tubing inserts into the inlet without the need for high voltage. For MAI, typically, 0.2 μL of matrix solution is drawn into the syringe before drawing 0.1 μL of the sample solution and dispensing to dry before insertion into the inlet. A comparison study of a mixture of angiotensin I, verapamil, crystal violet, and atrazine representative of peptides, drugs, dyes, and herbicides using SAI, MAI, and ESI shows large differences in ionization efficiency of the various components. Solutions of a mixture of erythromycin and azithromycin in wells of a 384-microtiter well plate were mass analyzed at the rate of ca 1 min per sample using MAI and ESI. In addition, we report the analysis of bacterial extracts using automated MAI and ESI methods. Finally, the ability to perform surface analysis with the automated platform is also demonstrated by directly analyzing dyes separated on a thin-layer chromatography (TLC) plate and compounds extracted from the surface of a beef liver tissue section. The prototype multi-ionization automated platform offers solid matrix introduction used with MAI, as well as solution introduction using either ESI or SAI. The combination of ionization methods extends the types of compounds which are efficiently ionized and is especially valuable with complex mixtures as demonstrated for bacterial extracts. While coupling of the automated multi-ionization platform to Thermo and Waters mass spectrometers is demonstrated, it should be possible to interface it with most commercial mass spectrometers.

Microdroplet Fusion Chemistry for Charge State Reduction of Synthetic Polymers via Bipolar Dual Spray with Anionic Reagents.

Microdroplet fusion chemistry is an emerging area of analyte manipulation that utilizes the ion source region of a mass spectrometer to covalently derivatize or manipulate the charge state distribution. This technique utilizes two electrospray emitters in close proximity, where the droplets from each electrospray plume fuse and undergo the subsequent chemistry. In this study, microdroplet fusion chemistry via bipolar dual spray has demonstrated the ability to reduce the average charge state of polyethylene glycol (PEG) cations using anionic reagents. Bipolar dual spray was implemented on a commercial mass spectrometer with limited hardware modifications to the ion source. Reagents including ammonium hydroxide, formic acid, and lithium chloride showed dramatic shifts in the average charge state of PEG 3.8K cations (e.g., 5.0+ to 2.5+) along with the emergence of newly detected charge states. An organic base, tributylamine, had no effect on the charge state distribution of PEG 3.8K cations. These results were consistent with an ion-pairing mechanism, where reagent anions destabilized ammonium cation interactions with PEG 3.8K upon droplet fusion from the negative and positive emitters. Additional bipolar dual spray experiments with PEG 12.6K demonstrated the ability to transform uninterpretable mass information into distinct charge states ranging from [M+8NH4]+ to [M+3NH4]+. Overall, this study provides insight into the nature of dual spray chemistry and will aid future experimental design in microdroplet covalent chemistry.

UV-Vis Photodissociation Action Spectroscopy on Thermo LTQ-XL ETD and Bruker amaZon Ion Trap Mass Spectrometers: a Practical Guide.

We report automated procedures for multiple tandem mass spectra acquisition allowing UV-Vis photodissociation action spectroscopy measurements of ions and radicals. The procedures were developed for two commercial ion trap mass spectrometers and applied to collision-induced and electron-transfer dissociation tandem mass spectrometry modes of ion generation.

Combining MALDI-2 and transmission geometry laser optics to achieve high sensitivity for ultra-high spatial resolution surface analysis.

A transmission geometry optical configuration allows for smaller laser spot size to facilitate high-resolution matrix-assisted laser/desorption ionization (MALDI) mass spectrometry. This increase in spatial resolution (ie, smaller laser spot size) is often associated with a decrease in analyte signal. MALDI-2 is a post-ionization technique, which irradiates ions and neutrals generated in the initial MALDI plume with a second orthogonal laser pulse, and has been shown to improve sensitivity. Herein, we have modified a commercial Orbitrap mass spectrometer to incorporate a transmission geometry MALDI source with MALDI-2 capabilities to improve sensitivity at higher spatial resolutions.

A laser ablation resonance ionisation mass spectrometer (LA-RIMS) for the detection of isotope ratios of uranium at ultra-trace concentrations from solid particles and solutions

A commercial MALDI mass spectrometer coupled with a tunable laser ionisation system can be used for the detection of uranium isotope ratios at trace levels.

Dual Emitter Nano-Electrospray Ionization Coupled to Differential Ion Mobility Spectrometry-Mass Spectrometry for Shotgun Lipidomics.

Current lipidomics workflows are centered around acquisition of large data sets followed by lengthy data processing. A dual nESI-DIMS-MS platform was developed to perform real-time relative quantification between samples, providing data required for biomarker discovery and validation more quickly than traditional ESI-MS approaches. Nanosprayer activity and DIMS compensation field settings were controlled by a LabVIEW program synced to the accumulation portion of the ion trap scan function, allowing for full integration of the platform with a commercial mass spectrometer. By comparing samples with short electrospray pulses rather than constant electrospray, the DIMS and MS performance is normalized within an experiment, as signals are compared between individual mass spectra (ms time scale) rather than individual experiments (min-hr time scale). The platform was validated with lipid standards and extracts from nitrogen-deprived microalgae. Dual nESI-DIMS requires minimal system modification and is compatible with all traditional ion activation techniques and mass analyzers, making it a versatile improvement to shotgun lipidomics workflows.

Detection of Inorganic Salt-Based Homemade Explosives (HME) by Atmospheric Flow Tube-Mass Spectrometry.

Using a commercial mass spectrometer interfaced with an atmospheric flow tube (AFT) allowed for the detection of a variety of inorganic compounds used as oxidizers in homemade explosives (HMEs) at picogram levels. The AFT provides reaction times of between 3 and 5 s with flows of 6 L/min, enabling detection levels, after thermal desorption, similar to those previously demonstrated for RDX vapor in the low parts per quadrillion range. The thermal desorption of chlorate and perchlorate salts resulted in the production of the corresponding anions which have higher electron affinities than that of the nitrate reactant ions. A dielectric barrier discharge, used as the ionization source, produced the nitrate reactant ions. In some instances, the molecular salt formed adducts with the nitrate, chlorate, and/or perchlorate anions, giving insight into the original identity of the salt cation. Urea nitrate, guanidine nitrate, and potassium nitrate were also detected as adducts with the nitrate reactant ion. The direct room-temperature vapor detection of urea nitrate and hydrogen peroxide, which have relatively high vapor pressures compared to the other salts in this study, is also demonstrated. Room-temperature vapor detection of chlorate and perchlorate salts is possible by the addition of a dilute acid which converts the salt into a more volatile acidic form. A discussion of the instrumentation, methods used, and the ionization chemistry is provided.

STUDY OF COMPONENT COMPOSITION OF MEDICINAL PLANT MATERIALS BY GAS CHROMATOGRAPHY WITH MASS-SPECTROMETRIC DETECTION

Component composition of extracts 14 medicinal materials kinds was study by gas chromatography with mass-spectrometric detection for revealing of the marker compounds specific for particular plant species. Extraction of components from the investigated objects was carried out by extraction of dry ground raw material with ethanol. For the analysis of polar compounds, the extracts were further derivatized to give the corresponding trimethylsilyl derivatives. Identification of components was carried out using commercial (NIST11, Wiley14) and own custom mass-spectrometer libraries. A number of compounds with species specificity were found for Schisandra chinensis, Ginkgo biloba, Oplopanax elatus, Oplopanax horridus, Ferula soongarica, Epimedium brevicornu, Epimedium koreanu, Cnidium Monnieri, Tribulus terrestris. The possibility of practical application of identified marker compounds for establishing the authenticity and quality control of multicomponent plant gathering and biologically active food additives on the example of the analysis BAA «Vertera Endo mix», «REDTEST», «Devil’s Club» is shown. Based on the analysis of extracts Panax ginseng, Aralia mandshurica, Rhodiola rosea, Eurycoma longifolia and Eleutherococcus senticosus, it was not possible to identify marker compounds

Evaluation of the New Capture Vaporizer for Aerosol Mass Spectrometers (AMS): Elemental Composition and Source Apportionment of Organic Aerosols (OA)

To reduce the quantification uncertainty of commercial aerosol mass spectrometers (AMS) and aerosol chemical speciation monitors (ACSM), a new capture vaporizer (CV) was recently built to replace the standard vaporizer (SV). A collection efficiency (CE) ∼ 1 in the CV AMS/ACSM has been demonstrated for ambient aerosols, but the CV also leads to increased thermal decomposition of the analytes because of longer residence time and vaporizer surface contact. This study reports on the performance of the CV for analyzing organic aerosol (OA) elemental composition and source apportionment, using both HR-ToF-AMS and ACSM for the first time. The methodology for obtaining elemental ratios from AMS spectra is updated to account for differences in OA fragmentation between the CV and SV. An artifact CO+ signal is observed for some chemically reduced laboratory compounds. If that signal is included in elemental analysis, the O:C is substantial overestimated, while accurate results are observed if the anomalous CO+ is ig...

Extensive study on physicochemical properties of polychlorinated biphenyls in a commercial ion trap mass spectrometer, relevance in analytical and environmental chemistry.

Polychlorinated biphenyls (PCBs) exist as 209 congeners, consisting of biphenyl molecules, where the number and substitution positions of halogen atoms are known to affect industrial uses, environmental transport mechanisms, distribution, fate, and toxicity. The complexity of the problem requires accurate physicochemical studies of an increasing number of congeners in order to understand the environmental and biological processes at play. This work presents a systematic study on the thermodynamic and kinetic properties of PCBs by quadrupole ion trap mass spectrometry. A clear relationship between structure and behavior of PCBs in mass spectrometry experiments has been observed. Overall data demonstrate that di-ortho congeners show lower thermodynamic stability and higher fragmentation rate than non/mono-ortho. Congeners follow different fragmentation mechanisms according to the number of chlorine atoms in ortho position of the biphenyl system. Experimental kinetic curves of mono/non-ortho and di-ortho congeners show a strong similarity with classical first-order kinetics curves; in particular, di-ortho congeners follow a first-order consecutive reaction, while mono/non-ortho follow a first-order parallel reaction. For each studied congener, the kinetic constant of reaction (fragmentation) has been determined. Data support environmental levels and biochemical transformations described in literature. The general picture of the PCB behavior inside a quadrupole ion trap provides the basis for the development of reliable and cost-effective analytical methods to the determination of ultra-low level trace of PCB congeners.

Digital Waveform Technology and the Next Generation of Mass Spectrometers.

Ion traps and guides are integral parts of current commercial mass spectrometers. They are currently operated with sinusoidal waveform technology that has been developed over many years. Recently, digital waveform technology has begun to emerge and promises to supplant its older cousin because it presents new capabilities that result from the ability to instantaneously switch the frequency and duty cycle of the waveforms. This manuscript examines these capabilities and reveals their uses and effects on instrumentation. Graphical Abstract ᅟ.

Laboratory-based validation of the baseline sensors of the ITER diagnostic residual gas analyzer

The divertor-specific ITER Diagnostic Residual Gas Analyzer (DRGA) will provide essential information relating to DT fusion plasma performance. This includes pulse-resolving measurements of the fuel isotopic mix reaching the pumping ducts, as well as the concentration of the helium generated as the ash of the fusion reaction. In the present baseline design, the cluster of sensors attached to this diagnostic's differentially pumped analysis chamber assembly includes a radiation compatible version of a commercial quadrupole mass spectrometer, as well as an optical gas analyzer using a plasma-based light excitation source. This paper reports on a laboratory study intended to validate the performance of this sensor cluster, with emphasis on the detection limit of the isotopic measurement. This validation study was carried out in a laboratory set-up that closely prototyped the analysis chamber assembly configuration of the baseline design. This includes an ITER-specific placement of the optical gas measurement downstream from the first turbine of the chamber's turbo-molecular pump to provide sufficient light emission while preserving the gas dynamics conditions that allow for \ extasciitilde 1 s response time from the sensor cluster [1].

Fast Determination of Ingredients in Solid Pharmaceuticals by Microwave-Enhanced In-Source Decay of Microwave Plasma Torch Mass Spectrometry

Rapid qualitative and quantitative analysis of solid samples (e.g., pharmaceutical preparations) by using a small and low-resolution mass spectrometer without MS/MS function is still a challenge in ambient pressure ionization mass spectrometric analysis. Herein, a practically efficient method termed microwave-enhanced in-source decay (MEISD) using microwave plasma torch desorption ionization coupled with time-of-flight mass spectrometry (MPTDI-TOF MS) was developed for fast analysis of pharmaceutical tablets using a miniature TOF mass spectrometer without tandem mass function. The intensity of ISD fragmentation was evaluated under different microwave power values. Several factors, including desorption distance and time that might affect the signal intensity and fragmentation, were systematically investigated. It was observed that both the protonated molecular ions and major fragment ions from the active ingredients in tablets could be found in the full-scan mass spectra in positive ion mode, which were comparable to those obtained by a commercial LTQ-XL ion trap mass spectrometer. The structures of the ingredients could be elucidated in detail using the MEISD method, which promotes our understanding of the desorption/ionization processes in microwave plasma torch (MPT). Quantitative analysis of 10 tablets was achieved by full-scan MPTDI-TOF MS with low limit of detection (LOD, 0.763 mg/g), acceptable relative standard deviation (RSD < 7.33%, n =10), and 10 s for each tablet, showing promising applications in high throughput screening of counterfeit drugs.Graphical ᅟ

Reducing mass peak instability caused by the phase changes of RF and AC signals in a rectilinear ion-trap analyzer.

For an ion trap with resonance ejection, peak intensity and peak position of the acquired mass spectra are affected by the phase difference between the radio frequency (RF) and auxiliary alternating current (AC) potentials. To ensure measurement stability, RF and AC phase-locking is commonly used in commercial ion trap mass spectrometers. In this study, a compact electronic control system was developed to accurately regulate the RF and AC phases and was employed in a photoionization rectilinear ion trap (RIT) mass spectrometer. We found that the phase-locking method was defective in multicomponent analysis because the optimal RF and AC phase difference was usually different for different m/z peaks. After studying and characterizing the relationship between the peaks and the RF and AC phases, a correction method based on data processing was used to improve the peaks' stability and accuracy. The results show that the fluctuations of both peak intensity and peak position were significantly reduced and that the instrument presented satisfying reproducibility and quantitative ability.

Real-time quadrupole mass spectrometry of hydrothermal gases from the unstable Pisciarelli fumaroles (Campi Flegrei): Trends, challenges and processes

Volcanic gas sampling and post-collection chemical determination in a laboratory may preclude any real-time continuous monitoring of volcanic activity. We describe the development, and show the advantages, of a system used for the continuous monitoring of fumarolic gases discharged from the Pisciarelli site (Campi Flegrei, Southern Italy) based on a commercial quadrupole mass spectrometer (QMS-301 Omnistar™). Although numerous technical problems were addressed due to the ephemeral nature of the emission point and the harsh environment, we also report measurements of the chemical composition of the major gas species emitted from the fumarole for two different periods (in 2009 and 2012). The CO2/H2S, H2S/H2, He/CO2 and CH4/CO2 molar ratios were investigated in order to detect magmatic and/or hydrothermal components in the system, while the N2/O2 ratio was adopted to infer other non-volcanic processes, such as air contamination and mixing with polluted surface waters. The presented methodology allows continuous gas sampling and provides the first evidence of short-term gas variations not available by direct sampling, which is often impractical and hazardous. Compared to the current techniques that are used worldwide for the full characterization of gaseous emissions, i.e. chemical analysis of traditional soda-filled under-vacuum bottles and MultiGAS surveys (laboratory-based and in situ, respectively), QMS-based monitoring is complementary and, in prospect, an alternative. With our method, the geochemical monitoring benefits of the real-time analysis for high sampling rates that can be made comparable to the continuous measurements of geophysical networks. This allows a better understanding of hydrothermal features, particularly of chemical fluctuations occurring on the very short-term, which is fundamental for the evaluation of the evolution of unrest episodes at Campi Flegrei, one of the most hazardous volcanic areas in the world.

Thermal Desorption Low Temperature Plasma Ionization Mass Spectrometry for Rapid and Sensitive Detection of Pesticides in Broomcorn

Abstract A thermal desorption low temperature plasma (TD-LTP) ionization source was developed for the direct, rapid and sensitive detection of pesticides by mass spectrometry without complex sample pretreatment. A thermal desorption sampler was added in front of the plasma generator, and the analyte was collected on a polytetrafluoroethylene (PTFE) swab and desorbed into gas molecules, and then gas molecules were transported to the plasma generator by carrier gas to be ionized. The utilization of thermal desorption sampler helped to transform the interaction between gas phase plasma and sample from gas-solid or gas-liquid to gas-gas, which greatly increased the sensitivity and stability especially for non-volatile sample (e.g. pesticides) compared with conventional LTP ionization source. The TD-LTP ionization source was coupled to a homemade rectilinear ion trap mass spectrometry. The operation parameters of the TD-LTP ionization source were optimized and the characteristic ions of 12 different pesticides were successfully obtained and investigated. Then the TD-LTP ionization source was connected with commercial ACQUITY TQD mass spectrometer, and the pesticide residue level in broomcorn was evaluated.

Detecting Low-Abundance Molecules at Single-Cell Level by Repeated Ion Accumulation in Ion Trap Mass Spectrometer.

Low-abundance metabolites or proteins in single-cell samples are usually undetectable by mass spectrometry (MS) due to the limited amount of substances in single cells. This limitation inspired us to further enhance the sensitivity of commercial mass spectrometers. Herein, we developed a technique named repeated ion accumulation by ion trap MS, which is capable of enhancing the sensitivity by selectively and repeatedly accumulating ions in a linear ion trap for up to 25 cycles. The increase in MS sensitivity was positively correlated with the number of repeated cycles. When ions were repeatedly accumulated for 25 cycles, the sensitivity of adenosine triphosphate detection was increased by 22-fold within 1.8 s. Our technique could stably detect low-abundance ions, especially MSn ions, at the single-cell level, such as 5-methylcytosine hydrolyzed from sample equivalent to ∼0.2 MCF7 cell. The strategy presented in this study offers the possibility to aid single-cell analysis by enhancing MS detection sensitivity.

Isotopic Analysis of 3He/4He by an Industrial EMG-20-8 Mass Spectrometer with Respect to Laboratory Units for Extracting 3He from Natural Helium

An apparatus and method for isotopic analysis of 3He/4He for controlling the extraction of 3He from natural He were designed using a commercial industrial mass spectrometer. A modernized sample-injection system allowed the sample volume of rare and expensive gases for quantitative and isotopic analyses to be reduced by 3–5 orders of magnitude. The metrological characteristics of the developed analytical method including sampling and injection into the mass spectrometer were evaluated using model analyses of individual isotopes of Ar, Ne, and He.

Effect of secondary organic aerosol coating thickness on the real-time detection and characterization of biomass-burning soot by two particle mass spectrometers

Abstract. Biomass burning is a large source of light-absorbing refractory black carbon (rBC) particles with a wide range of morphologies and sizes. The net radiative forcing from these particles is strongly dependent on the amount and composition of non-light-absorbing material internally mixed with the rBC and on the morphology of the mixed particles. Understanding how the mixing state and morphology of biomass-burning aerosol evolves in the atmosphere is critical for constraining the influence of these particles on radiative forcing and climate. We investigated the response of two commercial laser-based particle mass spectrometers, the vacuum ultraviolet (VUV) ablation LAAPTOF and the IR vaporization SP-AMS, to monodisperse biomass-burning particles as we sequentially coated the particles with secondary organic aerosol (SOA) from α-pinene ozonolysis. We studied three mobility-selected soot core sizes, each with a number of successively thicker coatings of SOA applied. Using IR laser vaporization, the SP-AMS had different changes in sensitivity to rBC compared to potassium as a function of applied SOA coatings. We show that this is due to different effective beam widths for the IR laser vaporization region of potassium versus black carbon. The SP-AMS's sensitivity to black carbon (BC) mass was not observed to plateau following successive SOA coatings, despite achieving high OA : BC mass ratios greater than 9. We also measured the ion fragmentation pattern of biomass-burning rBC and found it changed only slightly with increasing SOA mass. The average organic matter ion signal measured by the LAAPTOF demonstrated a positive correlation with the condensed SOA mass on individual particles, despite the inhomogeneity of the particle core compositions. This demonstrates that the LAAPTOF can obtain quantitative mass measurements of aged soot-particle composition from realistic biomass-burning particles with complex morphologies and composition.