Ryan M. Danell

The use of static pressures of heavy gases within a quadrupole ion trap.

The performance of quadrupole ion traps using argon or air as the buffer gas was evaluated and compared to the standard helium only operation. In all cases a pure buffer gas, not mixtures of gases, was investigated. Experiments were performed on a Bruker Esquire ion trap, a Finnigan LCQ, and a Finnigan ITMS for comparison. The heavier gases were found to have some advantages, particularly in the areas of sensitivity and collision-induced dissociation efficiency; however, there is a significant resolution loss due to dissociation and/or scattering of ions. Additionally, the heavier gases were found to affect ion activation and deactivation during MS/MS, influencing the product ion intensities observed. Finally, the specific quadrupole ion trap design and the ion ejection parameters were found to be crucial in the quality of the spectra obtained in the presence of heavy gases. Operation with static pressures of heavy gases can be beneficial under certain design and operating conditions of the quadrupole ion trap.

Pulsed Nano-Electrospray Ionization: Characterization of Temporal Response and Implementation with a Flared Inlet Capillary.

Abstract The temporal response of pulsed nano-electrospray ionization mass spectrometry (nano-ESI-MS) was studied and its influence on ion formation and detection was characterized. Rise and decay times for the mass resolved ion current were determined to be 20 ± 3 msec and 61 ± 5 msec, respectively, which led to a maximum pulse rate of 12 Hz. Pulsed nano-ESI operation was demonstrated from a multi-sprayer source controlled by a high voltage pulsing circuit constructed in-house. The desired source mode of operation (e.g. pulsing or continuous) can be realized solely by controlling the voltage applied to each sprayer.

Order of Magnitude Signal Gain in Magnetic Sector Mass Spectrometry Via Aperture Coding

AbstractMiniaturizing instruments for spectroscopic applications requires the designer to confront a tradeoff between instrument resolution and instrument throughput [and associated signal-to-background-ratio (SBR)]. This work demonstrates a solution to this tradeoff in sector mass spectrometry by the first application of one-dimensional (1D) spatially coded apertures, similar to those previously demonstrated in optics. This was accomplished by replacing the input slit of a simple 90° magnetic sector mass spectrometer with a specifically designed coded aperture, deriving the corresponding forward mathematical model and spectral reconstruction algorithm, and then utilizing the resulting system to measure and reconstruct the mass spectra of argon, acetone, and ethanol. We expect the application of coded apertures to sector instrument designs will lead to miniature mass spectrometers that maintain the high performance of larger instruments, enabling field detection of trace chemicals and point-of-use mass spectrometry. Graphical Abstractᅟ

MOMA: The Challenge to Search for Organics and Biosignatures on Mars

This paper describes strategies to search for, detect, and identify organic material on the surface and subsurface of Mars. The strategies described include those applied by landed missions in the past and those that will be applied in the future. The value and role of ESAs ExoMars rover and of her key science instrument Mars Organic Molecule Analyzer (MOMA) are critically assessed.

Mars Organic Molecule Analyzer (MOMA) mass spectrometer for ExoMars 2018 and beyond

The 2018 joint ESA-Roscosmos ExoMars rover mission will seek the signs of past or present life in the near-surface environment of Mars. The rover will obtain samples from as deep as two meters beneath the surface and deliver them to an onboard analytical laboratory for detailed examination. The Mars Organic Molecule Analyzer (MOMA) investigation forms a core part of the sample analysis capability of ExoMars. Its top objective is to address the main “life signs” goal of the mission through detailed chemical analysis of the acquired samples. MOMA characterizes organic compounds in the samples with a novel dual ion source ion trap mass spectrometer (ITMS). The ITMS supports both pyrolysis-gas chromatography (pyr-GC) and Mars ambient laser desorption/ionization (LDI) analyses in an extremely compact package. Combined with the unprecedented depth sampling capability of ExoMars, MOMA affords a broad and powerful search for organics over a range of preservational environments, volatility, and molecular weight.

Design and demonstration of the Mars Organic Molecule Analyzer (MOMA) on the ExoMars 2018 rover

The Mars Organic Molecule Analyzer (MOMA) investigation is a key astrobiology experiment scheduled to launch on the joint ESA-Roscosmos ExoMars 2018 rover mission. MOMA will examine the chemical composition of geological samples acquired from depths of up to two meters below the martian surface, where fragile organic molecules may be protected from destructive cosmic radiation and/or oxidative chemical reactions. The heart of the MOMA mass spectrometer subsystem (i.e., MOMA-MS) is a miniaturized linear ion trap (LIT) that supports two distinct modes of operation to detect: i) volatile and semi-volatile, low-to-moderate mass organics (≤500 Da) via pyrolysis coupled with gas chromatography mass spectrometry (pyr/GCMS); and, ii) more refractory, moderate-to-high mass compounds (up to 1000 Da) via laser desorption (LDMS) at ambient Mars pressures. Additionally, the LIT mass analyzer enables selective ion trapping via multi-frequency waveform ion excitation (e.g., stored waveform inverse Fourier transform, or SWIFT), and structural characterization of complex molecules using tandem mass spectrometry (MS/MS). A high-fidelity Engineering Test Unit (ETU) of MOMA-MS, including the LIT subassembly, dual-gun electron ionization source, micropirani pressure gauge, solenoid-driven aperture valve, redundant detection chains, and control electronics, has been built and tested at NASA GSFC under relevant operational conditions (pressure, temperature, etc.). Spaceflight qualifications of individual hardware components and integrated subassemblies have been validated through vibration, shock, thermal, lifetime, and performance evaluations. The ETU serves as a pathfinder for the flight model buildup, integration and test, as the ETU meets the form, fit and function of the flight unit that will be delivered to MPS in late 2015. To date, the ETU of MOMA-MS has been shown to meet or exceed all functional requirements, including mass range, resolution, accuracy, instrumental drift, and limit-of-detection specifications, thereby enabling the primary science objectives of the MOMA investigation and ExoMars 2018 mission.

Two-Dimensional Aperture Coding for Magnetic Sector Mass Spectrometry

AbstractIn mass spectrometer design, there has been a historic belief that there exists a fundamental trade-off between instrument size, throughput, and resolution. When miniaturizing a traditional system, performance loss in either resolution or throughput would be expected. However, in optical spectroscopy, both one-dimensional (1D) and two-dimensional (2D) aperture coding have been used for many years to break a similar trade-off. To provide a viable path to miniaturization for harsh environment field applications, we are investigating similar concepts in sector mass spectrometry. Recently, we demonstrated the viability of 1D aperture coding and here we provide a first investigation of 2D coding. In coded optical spectroscopy, 2D coding is preferred because of increased measurement diversity for improved conditioning and robustness of the result. To investigate its viability in mass spectrometry, analytes of argon, acetone, and ethanol were detected using a custom 90-degree magnetic sector mass spectrometer incorporating 2D coded apertures. We developed a mathematical forward model and reconstruction algorithm to successfully reconstruct the mass spectra from the 2D spatially coded ion positions. This 2D coding enabled a 3.5× throughput increase with minimal decrease in resolution. Several challenges were overcome in the mass spectrometer design to enable this coding, including the need for large uniform ion flux, a wide gap magnetic sector that maintains field uniformity, and a high resolution 2D detection system for ion imaging. Furthermore, micro-fabricated 2D coded apertures incorporating support structures were developed to provide a viable design that allowed ion transmission through the open elements of the code. Graphical Abstractᅟ

Compressive Mass Analysis on Quadrupole Ion Trap Systems

AbstractConventionally, quadrupole ion trap mass spectrometers eject ions of different mass-to-charge ratio (m/z) in a sequential fashion by performing a scan of the rf trapping voltage amplitude. Due to the inherent sparsity of most mass spectra, the detector measures no signal for much of the scan time. By exploiting this sparsity property, we propose a new compressive and multiplexed mass analysis approach—multi Resonant Frequency Excitation (mRFE) ejection. This new approach divides the mass spectrum into several mass subranges and detects all the subrange spectra in parallel for increased mass analysis speed. Mathematical estimation of standard mass spectrum is demonstrated while statistical classification on the parallel measurements remains viable because of the sparse nature of the mass spectra. This method can reduce mass analysis time by a factor of 3–6 and increase system duty cycle by 2×. The combination of reduced analysis time and accurate compound classification is demonstrated in a commercial quadrupole ion trap (QIT) system. Figureᅟ

Detection of trace organics in Mars analog samples containing perchlorate by laser desorption/ionization mass spectrometry.

Evidence from recent Mars missions indicates the presence of perchlorate salts up to 1 wt % level in the near-surface materials. Mixed perchlorates and other oxychlorine species may complicate the detection of organic molecules in bulk martian samples when using pyrolysis techniques. To address this analytical challenge, we report here results of laboratory measurements with laser desorption mass spectrometry, including analyses performed on both commercial and Mars Organic Molecule Analyzer (MOMA) breadboard instruments. We demonstrate that the detection of nonvolatile organics in selected spiked mineral-matrix materials by laser desorption/ionization (LDI) mass spectrometry is not inhibited by the presence of up to 1 wt % perchlorate salt. The organics in the sample are not significantly degraded or combusted in the LDI process, and the parent molecular ion is retained in the mass spectrum. The LDI technique provides distinct potential benefits for the detection of organics in situ on the martian surface and has the potential to aid in the search for signs of life on Mars.

A new approach for effecting surface-induced dissociation in an ion cyclotron resonance mass spectrometer: a modeling study

With the increasing use of ion cyclotron resonance (ICR) for tandem mass spectrometry (MS/MS) analysis of biomolecules, surface-induced dissociation (SID) should be given serious consideration as an ion activation technique. There are at least two compelling reasons to consider SID: it can deposit significant amounts of internal energy into large ions, and no collision gas is required. These potential advantages have led us to undertake a modeling study of the SID process in an ICR using the ion optics program SIMION. The various methods previously used to obtain SID spectra are compared to a new approach for effecting SID in an ICR. Through simulations, many different parameters present in the experiment are correlated to the kinetic energy of the parent ion upon impact and the overall product ion collection efficiency (and hence the signal intensity) expected. The modeling results suggest this new approach allows larger, more precise, and controllable impact energies to be used, as well as providing higher collection efficiencies. The validity of the modeling results is supported by good qualitative agreement with previously reported experimental results.