Miniature mass analyzers

Underwater mass spectrometry systems can be used for direct in situ detection of volatile organic compounds and dissolved gases in oceans, lakes, rivers and waste-water streams. In this work we describe the design and operation of (1) a linear quadrupole mass filter and (2) a quadrupole ion trap mass spectrometer interfaced, in each case, with a membrane introduction/fluid control system and packaged for underwater operation. These mass spectrometry systems can operate autonomously, or under user control via a wireless rf link. Detection limits for each system were determined in the laboratory using pure solutions. The quadrupole mass filter system provides detection limits in the 1-5 ppb range with an upper mass limit of 100 amu. Its power requirement is approximately 95 Watts. The ion trap system has detection limits well below 1 ppb, an upper mass limit of 650 amu and MS/MS capability. Its power consumption is on the order of 150 Watts. The present membrane limits analysis to non-polar compounds (Ͻ300 amu) with analysis cycles of 5-15 minutes. Deployments of both types of instruments are described, along with a discussion of the challenges associated with in-water mass spectrometry and descriptions of alternative in-water mass spectrometer configurations. (J Am Soc Mass Spectrom 2001, 12, 676 -682 ) © 2001 American Society for Mass Spectrometry S tandard methods for analysis of aqueous systems typically involve collection of samples and delivery to a laboratory for analysis [1]. Inherent in this practice is the possibility of both contamination and loss of analytes, particularly in the case of highly reactive or volatile species. In addition, this type of sampling severely limits both spatial and temporal sampling densities. A particularly important limitation of long collection/analysis cycles is the inability to implement adaptive sampling. Appropriate monitoring of dynamic biogeochemical systems requires rapid sampling adaptations in response to rapidly varying analyte distributions [2]. Intelligent sampling strategies are required to adequately characterize vast bodies of water that influence, and are influenced by, human activities. Since mass spectrometry is arguably the most versatile of chemical sensors, we have undertaken development of in situ mass spectrometry systems capable of real-time, adaptive in-water analyses.Although mass spectrometry has been used in the laboratory for an extremely wide variety of chemical analyses, from precise isotopic ratio measurements [3] to DNA sequencing [4 -6], no single configuration of mass analyzer and sample interface is appropriate for all types of measurements. This is evidenced in recent reviews of field analytical techniques [7] and advances in miniaturization of mass spectrometers [8]. Accordingly, we have chosen a modular approach for development of immersion mass spectrometers. Initially, simpler designs are used to integrate available components, and simultaneously new subsystems are being developed for evolving reconfigurations capable of accessing a w...

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confidence: 99%

Underwater mass spectrometers for in situ chemical analysis of the hydrosphere

Short

Fries

Kerr

et al. 2001

“…Several adroit methods were exploited to discriminate between isobaric ions. A second inlet routed the sample through a getter pump to adsorb H 2 and enable collection of additional data to discriminate between 3 He and HD. This instrument provided unanticipated results insofar as the Venusian atmosphere was found to contain 96% CO 2 and 4% N 2 , as well as more primordial argon (as indicated by a high ratio of 36 Ar to 40 Ar) than found on Earth.…”

Section: Pioneer Venus Probementioning

confidence: 99%

“…These instruments were enthusiastically marketed and sold by a variety of instrument manufacturers. Recent research and engineering advances have led to further reductions in the size of mass spectrometers and resulted in the development of new ones based on novel approaches [1][2][3]. Although these miniaturized mass spectrometers have not been embraced by the major instrument manufacturers because of perceptions of limited markets and/or profit margins, the National Aeronautics and Space Administration (NASA) has supported their development because of its need for small, analytically powerful instruments to further its goals for the exploration of space.…”

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confidence: 99%

Mass spectrometry in the U.S. space program: Past, present, and future

Palmer

Limero

2001

Recent years have witnessed significant progress on the miniaturization of mass spectrometers for a variety of field applications. This article describes the development and application of mass spectrometry (MS) instrumentation to support of goals of the U.S. space program. Its main focus is on the two most common space-related applications of MS: studying the composition of planetary atmospheres and monitoring air quality on manned space missions. Both sets of applications present special requirements in terms of analytical performance (sensitivity, selectivity, speed, etc.), logistical considerations (space, weight, and power requirements), and deployment in perhaps the harshest of all possible environments (space). The MS instruments deployed on the Pioneer Venus and Mars Viking Lander missions are reviewed for the purposes of illustrating the unique features of the sample introduction systems, mass analyzers, and vacuum systems, and for presenting their specifications which are impressive even by today's standards. The various approaches for monitoring volatile organic compounds (VOCs) in cabin atmospheres are also reviewed. In the past, ground-based GC/MS instruments have been used to identify and quantify VOCs in archival samples collected during the Mercury, Apollo, Skylab, Space Shuttle, and Mir missions. Some of the data from the more recent missions are provided to illustrate the composition data obtained and to underscore the need for instrumentation to perform such monitoring in situ. Lastly, the development of two emerging technologies, Direct Sampling Ion Trap Mass Spectrometry (DSITMS) and GC/Ion Mobility Spectrometry (GC/IMS), will be discussed to illustrate their potential utility for future missions. (J Am Soc Mass Spectrom 2001, 12, 656 -675)

“…A maximum resolution of M/⌬M ϭ 87 at 10% peak height has been achieved at m/z ϭ 219 with a filter operated at 6 MHz and constructed using rods measuring ( nterest in the miniaturization of mass analyzers has been growing rapidly in recent years, largely driven by the need for compact, lightweight systems for use in environmental, security, and space applications. While there have been numerous attempts to make small analyzers, not all can reasonably be called miniature [1]. However, quadrupole mass filters [2-6] and various types of ion traps [7][8][9] with characteristic dimensions of the order of a few millimeters or less have been demonstrated.…”

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confidence: 99%

Comparison of ion coupling strategies for a microengineered quadrupole mass filter

Wright¹,

Syms

O'Prey³

et al. 2009

The limitations of conventional machining and assembly techniques require that designs for quadrupole mass analyzers with rod diameters less than a millimeter are not merely scale versions of larger instruments. We show how silicon planar processing techniques and microelectromechanical systems (MEMS) design concepts can be used to incorporate complex features into the construction of a miniature quadrupole mass filter chip that could not easily be achieved using other microengineering approaches. Three designs for the entrance and exit to the filter consistent with the chosen materials and techniques have been evaluated. The differences between these seemingly similar structures have a significant effect on the performance. Although one of the designs results in severe attenuation of transmission with increasing mass, the other two can be scanned to m/z ϭ 400 without any corruption of the mass spectrum. At m/z ϭ 219, the variation in the transmission of the three designs was found to be approximately four orders of magnitude. A maximum resolution of M/⌬M ϭ 87 at 10% peak height has been achieved at m/z ϭ 219 with a filter operated at 6 MHz and constructed using rods measuring ( nterest in the miniaturization of mass analyzers has been growing rapidly in recent years, largely driven by the need for compact, lightweight systems for use in environmental, security, and space applications. While there have been numerous attempts to make small analyzers, not all can reasonably be called miniature [1]. However, quadrupole mass filters [2-6] and various types of ion traps [7][8][9] with characteristic dimensions of the order of a few millimeters or less have been demonstrated. The size and weight contribution to a complete mass spectrometer system is not the only benefit of a miniaturized quadrupole mass filter. The rf amplitude required to achieve a particular mass range increases with the square of the rod radius. Hence, the rf supplies for miniature filters can be smaller and require less power than those needed for larger filters. More importantly, smaller pumps may be used, as the short path length of ions in the filter means that a higher pressure can be tolerated. Although this paper is focused on miniaturization of the filter, reports on the development of other miniaturized components that might be incorporated into a system, such as ion sources, gauges, and pumps can be found elsewhere [10 -12].The factors that determine the size of a miniature quadrupole mass filter are the required signal level, the accuracy of the construction technique, and the number of rf cycles needed to achieve the desired resolution. Clearly, as the size of the entrance aperture decreases, there will be an inevitable loss of signal, although some of this can be recovered through the use of an array [2,4]. There is a well-known correlation [13] between the fractional geometrical error and ultimate resolution. Hence, one fundamental limitation is set by the accuracy of the fabrication technique and the minimum acceptable resolution. Si...