Boris Brkić

Development of quadrupole mass spectrometers using rapid prototyping technology

In this report, we present a prototype design of a quadrupole mass filter (QMF) with hyperbolic electrodes, fabricated at the University of Liverpool using digital light processing (DLP), a low-cost and lightweight 3D rapid prototyping (RP) technique. Experimental mass spectra are shown for H2+, D2+, and He+ ions to provide proof of principle that the DLP mass filter is working as a mass analyzer in the low-mass range (1 to 10 amu). The performance of the DLP QMF has also been investigated for individual spectral peaks. Numerical simulations of the instrument were performed by coupling CPO and Liverpool QMS-2 programs to model both the ion source and mass filter, respectively, and the instrument is shown to perform as predicted by theory. DLP thus allows miniaturization of mass spectrometers at low cost, using hyperbolic (or other) geometries of mass analyzer electrodes that provide optimal ion manipulation and resolution for a given application. The potential of using RP fabrication techniques for developing miniature and microscale mass analyzers is also discussed.

Membrane Inlet Mass Spectrometry for Homeland Security and Forensic Applications

AbstractA man-portable membrane inlet mass spectrometer has been built and tested to detect and monitor characteristic odors emitted from the human body and also from threat substances. In each case, a heated membrane sampling probe was used. During human scent monitoring experiments, data were obtained for inorganic gases and volatile organic compounds emitted from human breath and sweat in a confined space. Volatile emissions were detected from the human body at low ppb concentrations. Experiments with compounds associated with narcotics, explosives, and chemical warfare agents were conducted for a range of membrane types. Test compounds included methyl benzoate (odor signature of cocaine), piperidine (precursor in clandestine phencyclidine manufacturing processes), 2-nitrotoluene (breakdown product of TNT), cyclohexanone (volatile signature of plastic explosives), dimethyl methylphosphonate (used in sarin and soman nerve agent production), and 2-chloroethyl ethyl sulfide (simulant compound for sulfur mustard gas). Gas phase calibration experiments were performed allowing sub-ppb LOD to be established. The results showed excellent linearity versus concentration and rapid membrane response times. Graphical Abstractᅟ

Oil-in-Water Monitoring Using Membrane Inlet Mass Spectrometry

A membrane inlet mass spectrometry (MIMS) system has been used for detection and analysis of two types of North Sea crude oil. The system was installed on-field on the Flotta Oil Terminal (Orkney, UK). It consisted of a quadrupole mass spectrometer (QMS) connected to the capillary probe with a silicone-based membrane. The produced mass spectra and calibration plots from the MIMS instrument showed the capability to measure levels of individual hydrocarbons within crude oil in seawater. The generated mass spectra from the field tests also showed the ability to distinguish between different types of oil and to determine concentrations of toxic hydrocarbons in oil (e.g., benzene, toluene, and xylene (BTX)). The performance of the instrument at different temperatures of seawater and oil droplet sizes was also investigated. The results showed that the QMS-based MIMS system has a potential to complement existing oil-in-water (OiW) monitors by being able to detect different oil types and specific hydrocarbon concentrations with high accuracy, which are currently not supported in commercially available OiW monitors.

Linear ion trap fabricated using rapid manufacturing technology

This article presents the design, construction, and test results of a linear ion trap, fabricated using digital light processing (DLP), which is a low-cost 3D layer-based manufacturing technique. The ion trap was incorporated into a portable mass spectrometer system and experimental mass spectrum was obtained for methamphetamine (m/z 182), cocaine (m/z 304), and rhodamine B (m/z 443), with a maximum observed resolution (FWHM) of 260. For rhodamine B, tandem MS capability is also demonstrated. The mass range (and resolution at higher m/z) of the instrument is also demonstrated by spectrum obtained from Ultramark (m/z 1621). The spectra obtained for the DLP trap occur at a considerably lower rf voltage than a rectilinear ion trap of similar size, which is a consequence of the hyperbolic electrode geometry and, hence, smaller r0 in the DLP case. High mass range with low voltage operation is especially important with regard to ‘in the field’ applications requiring low power consumption for extended periods of operation.

Monitoring of human chemical signatures using membrane inlet mass spectrometry.

This work is an attempt to assist border security crackdown on illegal human immigration, by providing essential results on human chemical signatures. Data was obtained using a portable quadrupole mass spectrometer coupled with a membrane probe for volunteers of both genders and under different conditions in a container simulator. During experiments, participants were asked to follow various protocols while volatile organic compounds emitted from their breath, sweat, skin, and other biological excretes were continuously being monitored. Experimental setups using different membrane materials (both hydrophilic and hydrophobic) including heating of the sampling probe and sampling flow rates were examined. From our measurements, significant information was obtained for NH3, CO2, water, and volatile organic compounds levels, illustrating a human chemical profile and indicating human presence in a confined space.

High-fidelity simulations of ion trajectories in miniature ion traps using the boundary-element method

In this paper we present numerical modeling results for endcap and linear ion traps, used for experiments at the National Physical Laboratory in the U.K. and Innsbruck University respectively. The secular frequencies for {sup 88}Sr{sup +} and {sup 40}Ca{sup +} ions were calculated from ion trajectories, simulated using boundary-element and finite-difference numerical methods. The results were compared against experimental measurements. Both numerical methods showed high accuracy with boundary-element method being more accurate. Such simulations can be useful tools for designing new traps and trap arrays. They can also be used for obtaining precise trapping parameters for desired ion control when no analytical approach is possible as well as for investigating the ion heating rates due to thermal electronic noise.

Effect of an Axial Magnetic Field on the Performance of a Quadrupole Mass Spectrometer

We consider the case of a quadrupole mass spectrometer (QMS) in which a static magnetic field is applied axially in the z-direction along the length of the mass filter. The theoretical approach assumed in the model is that the QMS contains hyperbolic rods as electrodes and that the magnetic field acts over the full length of the mass filter assembly. Initial experimental results with argon and helium for a low-resolution instrument confirm the predicted theoretical trends. The analysis also predicts for which values of operating parameters an enhancement of the instrument resolution is achieved when an axial magnetic field is applied. The model predicts instrument resolution R > 3000 for a QMS with a 200 mm long mass filter via application of an axial magnetic field.

Analysis of chlorinated hydrocarbons in gas phase using a portable membrane inlet mass spectrometer

A compact portable membrane inlet mass spectrometer (MIMS) has been used for the first time to detect and monitor, both qualitatively and quantitatively, volatile chlorinated hydrocarbons in the gaseous phase. Continuous monitoring of such compounds in the field is of importance due to their wide industrial use and their potential negative impact on public health and the environment. Compounds tested include vinyl chloride, 1,1-dichloroethylene, trichloroethylene and tetrachloroethylene. Gas phase experiments were performed at concentration levels from low ppb to low ppm. The results obtained showed very good linearity within the examined concentration range, ppb limits of detection and fast response (rise and fall) times. Mixture effects are also presented. The MIMS system was also investigated under periodic and dynamic experimental conditions and demonstrated stable and repeatable measurements.

Analysis of Fission Gas Release Kinetics by On-Line Mass Spectrometry

The release of fission gas (Xe and Kr) and helium out of nuclear fuel materials in normal operation of a nuclear power reactor can constitute a strong limitation of the fuel lifetime. Moreover, radioactive isotopes of Xe and Kr contribute significantly to the global radiological source term released in the primary coolant circuit in case of accidental situations accompanied by fuel rod loss of integrity. As a consequence, fission gas release investigation is of prime importance for the nuclear fuel cycle economy, and is the driven force of numerous R&D programs. In this domain, for solving current fuel behavior understanding issues, preparing the development of new fuels (e.g. for Gen IV power systems) and for improving the modeling prediction capability, there is a marked need for innovations in the instrumentation field, mainly for: • Quantification of very low fission gas concentrations, released from fuel sample and routed in sweeping lines • Monitoring of quick gas release variations by quantification of elementary release during a short period of time • Detection of a large range of atomic masses (e.g. H 2 , HT, He, CO, CO 2 , Ne, Ar, Kr, Xe), together with a performing separation of isotopes for Xe and Kr elements • Coupling measurement of stable and radioactive gas isotopes, by using in parallel mass spectrometry and gamma spectrometry techniques. To fulfill these challenging needs, a common strategy for analysis equipment implementation has been set up thanks to a recently launched collaboration between the CEA and the University of Provence, with the technological support of the Liverpool University. It aims at developing a chronological series of mass spectrometer devices based upon mass filter and 2D/3D ion traps with Fourier transform operating mode and having increasing levels of performances to match the previous challenges for out-of pile and in-pile experiments. The final objective is to install a high performance online mass spectrometer coupled to a gamma spectrometer in the fission product laboratory of the future Jules Horowitz Material Test Reactor. An intermediate step will consist of testing first equipment on an existing experimental facility in the LECA-STAR Hot Cell Laboratory of the CEA Cadarache. This paper presents the scientific and operational stakes linked to fission gas issues, resumes the current state of art for analyzing them in nuclear facilities, then presents the skills gathered through this collaboration to overcome technological bottlenecks. Finally it describes the implementation strategy in nuclear research facilities of the CEA Cadarache.

Modelling of Miniature Ion Traps for Quantum Computing

Ion traps are one of the leading technologies for the implementation of quantum computers in hardware. They are a vacuum technology that captures small number of laser‐cooled ions in a linear trap and uses their quantum states to construct quantum circuits. We present the simulation results for quantum computing in a miniature ion trap in order to investigate electrostatics, ion motion and trapping efficiency for a given electrode geometry.