2009. "Use of an ambient ionization flowing atmospheric-pressure afterglow source for elemental analysis through hydride generation." Journal of Analytical Atomic Spectrometry 24(1):34-40. Abstract An ambient mass spectrometry ionization source based on an atmospheric-pressure flowing afterglow has been coupled to a Mattauch-Herzog mass spectrograph capable of simultaneous acquisition of a range of mass-to-charge values by means of a Faraday-strip array detector. The flowing afterglow was used as the ionization pathway for species produced by hydride generation. This ionization strategy circumvents problems, such as discharge instabilities or memory effects, induced by introducing the gaseous sample into the discharge. The generated spectra show both atomic and molecular peaks; calibration curves were calculated for both peak types with limits of detection for arsenic below 10 ppb. This study demonstrates the ability to use an ambient mass spectrometry source, commonly used for molecular analyses, for the detection of gas phase elemental species with the possibilty of performing speciation by coupling with a separation technique.
2007. "Continuous Simultaneous Detection in Mass Spectrometry." Analytical Chemistry 79(20):7662-7668. doi:10.1021/ac070785s Abstract In mass spectrometry, several advantages can be derived when multiple mass-to-charge values are detected simultaneously. One such advantage is an improved duty cycle, which leads to superior limits of detection, better precision, shorter analysis times, and reduced sample sizes. A second advantage is the ability to reduce correlated noise by taking the ratio of two or more simultaneously collected signals, enabling greatly enhanced isotope ratio data. A final advantage is the elimination of spectral skew, leading to more accurate transient signal analysis. Here, these advantages are demonstrated by means of a novel Faraday-strip array detector coupled to a Mattauch-Herzog mass spectrograph. The same system is used to monitor elemental fractionation phenomena in laser ablation inductively coupled plasma mass spectrometry.
2007. "The Structure of a Cyanobacterial Bicarbonate Transport Protein, CmpA." Journal of Biological Chemistry 282(4):2606-2614. doi:10.1074/jbc.M610222200 Abstract Cyanobacteria, blue-green algae, are the most abundant autotrophs in aquatic environments and form the base of the food chain by fixing carbon and nitrogen into cellular biomass. To compensate for the low selectivity of Rubisco for CO₂ over O₂, Cyanobacteria have developed highly efficient CO₂concentrating machinery of which the ABC transport system CmpABCD from Synechocystis PCC 6803 is one component. Here we describe the structure of the bicarbonate binding protein, CmpA, in the absence and presence of bicarbonate and carbonic acid. CmpA is highly homologous to the nitrate transport protein, NrtA. CmpA binds carbonic acid at the entrance to the ligand-binding pocket whereas bicarbonate binds in nearly an identical location compared to nitrate binding to NrtA. Unexpectedly, bicarbonate binding is accompanied by a metal ion, identified as Ca²⁺ via inductively coupled plasma optical emission spectrometry. The binding of bicarbonate and metal is highly cooperative and suggests that CmpA co-transports bicarbonate and calcium.
2007. "Metallomics - An Interdisciplinary and Evolving Field." Journal of Analytical Atomic Spectrometry 22(8):855. doi:10.1039/b710205b Abstract In an editorial earlier this year (JAAS, 22, 111, 2007), we opined that metallomics, the study of metals in biological systems, would be an increasingly important topic in elemental analysis in general and for this journal in particular . This issue of the journal, co-edited by the two of us, is a second special issue covering the subject of Metallomics (the first issue was JAAS, 19/1, 2004). The present issue is comprised of technique, application, and perspective papers that address this emerging field of study and show how atomic spectrometry is contributing to the understanding of biological systems. The subjects covered range from metal binding in plants through investigations of metal and metalloids in samples of biological fluids to the study of food supplements and drug interactions in cells. The issue includes two Critical Reviews. Yuxi Gao and colleagues discuss advanced nuclear analytical techniques for the emerging field of metalloproteomics. While Laura Liermann and her colleagues consider how micro-organisms extract metals from minerals in the environment for utilization in metabolic processes. The content of some of these papers stretches the traditional boundaries and scope of this journal, as echoed by the reviewers of some of the papers. This discussion about scope requires perhaps further debate. However, it is our view that while the Journal must remain true to its core aims, it must also strive to accommodate and motivate a wider authorship and readership. Metallomics is a field that transcends biology and microbiology, biochemistry, clinical chemistry, environmental chemistry, geochemistry, and yes, atomic spectroscopy. If JAAS aspires to be a leading force in metallomics, the Journal must expand its horizons beyond traditional analytical spectroscopy per se. Accordingly, in this special issue you will find papers that have a heavy clinical emphasis, which speak to complementary (non-atomic) spectroscopic techniques, and that provide perspectives that only touch on the use of atomic spectroscopy. The field of metallomics is still in the process of being defined and we hope to inform that definition by including the widest body of technical literature on the subject. We hope that you will find these contributions to be informative, inspiring, and enlightening and consider submitting your own research in this area to JAAS.
2007. " Metallomics – The Future of Atomic Spectroscopy? ." Journal of Analytical Atomic Spectrometry 22(2):111. doi:10.1039/b618394h Abstract Metallomics is defined as the study of metals and metal species, and their interactions, transformations, and functions in biological systems. The full complement of metals and metal moieties (free and bound) is accordingly known as the metallome. The terms are relatively new ones, first coined by R.J.P. Williams of Oxford University and Hiroki Haraguchi of Nagoya University early in the present millennium. Metallomics is a new moniker for the field of bioinorganic chemistry, extending and broadening that discipline much as genomics has done for genetics, and is appositely harmonious with other ‘ohmics’ terms like genomics, proteomics, and metabolomics. Metallomics is also distinguished from other terms (e.g. speciation) by consideration of the global role of all metals/metalloids in a system.
2006. "Characterization of a Second-generation Focal-plane Camera Coupled to an Inductively Coupled Plasma Mattauch-Herzog Geometry Mass Spectrograph." Analytical Chemistry 78(13):4319-4325. Abstract A second-generation Faraday-strip array detector has been coupled to an inductively coupled plasma Mattauch- Herzog geometry mass spectrograph, thereby offering simultaneous acquisition of a range of mass-to-charge ratios. The second-generation device incorporates narrower, more closely spaced collectors than the earlier system. Furthermore, the new camera can acquire signal on all collectors at a frequency greater than 2 kHz and has the ability to independently adjust the gain level of each collector. Each collector can also be reset independently. With these improvements, limits of detection in the hundreds of picograms per liter for metals in solution have been obtained. Some additional features, such as a broader linear dynamic range (over 7 orders of magnitude), greater resolving power (up to 600), and improved isotope ratio accuracy were attained. In addition, isotope ratio precision as low as 0.018% RSD was achieved.
2006. "Electrothermal vaporization coupled with inductively coupled plasma array-detector mass spectrometry for the multielement analysis of Al2O3 ceramic powders." Spectrochimica Acta. Part B, Atomic Spectroscopy 61(1):42-49. Abstract An electrothermal vaporization (ETV) system useful for the analysis of solutions and slurries has been coupled with a sector-field inductively coupled plasma mass spectrometer (ICP-MS) equipped with an array detector. The ability of this instrument to record the transient signals produced in ETV-ICP-MS is demonstrated. Detection limits for Mn, Fe, Co, Ni, Cu, Zn and Ga are in the range of 4-60 pg µL-1 for aqueous solutions and in the low µg g-1 range for the analysis of 10 mg mL-1 slurries of Al2O3 powders. The dynamic ranges measured for Fe, Cu and Ga spanned 3-5 orders of magnitude when the detector was operated in the low-gain mode and appear to be limited by the ETV system. Trace amounts of Fe, Cu and Ga could be directly determined in Al2O3 powders at the 2-270 µg g-1 level without the use of thermochemical reagents. The results well agree with literature values for Fe, whereas deviations of 30-50% at the 2-90 µg g-1 level for Cu and Ga were found.
2006. "JAAS - 20 Years of Manuscripts, Citations, and Scientific Impact ." Journal of Analytical Atomic Spectrometry 21(3):259-262. doi:10.1039/b601801g Abstract David W. Koppenaal is a Laboratory Fellow, and Associate Director of the Biological Sciences Division at Pacific Northwest National Laboratory. He has been a member of the JAAS Editorial Board since 2000. Dr. Koppenaal first published in JAAS in 1988, and was recently guest editor for a 2004 special issue on Collision & Reaction Cells in Atomic Mass Spectrometry. He is currently also arranging a special issue on Metallomics for early 2007 publication. Dr. Koppenaal’s research interests include atomic mass spectrometry instrumentation and applications, with special interests in interference reduction using collision/reaction cells, high-resolution MS techniques using ion traps, new generation MS detectors, and radionuclear and metallomic applications of ICPMS.
2005. "Read-Noise Characterization of Focal Plane Array Detectors via Mean-Variance Analysis." Applied Spectroscopy 59(11):1315-1323. Abstract Mean-variance analysis is described as a method for characterization of the read-noise and gain of Focal Plane Array (FPA) detectors, including CCDs, CIDs, and CMOS multiplexers (IR arrays). Practical FPA detector characterization is outlined. The non-destructive readout capability available in some FPA devices is discussed as a means for signal-to-noise ratio improvement. Derivations of the equations are fully presented to unify understanding of this method by the spectroscopic community.
2005. "MS Detectors." Analytical Chemistry 77(21):418A-427A. Abstract Good eyesight is often taken for granted, a situation that everyone appreciates once vision begins to fade with age. New eyeglasses or contact lenses are traditional ways to improve vision, but recent new technology, i.e. LASIK laser eye surgery, provides a new and exciting means for marked vision restoration and improvement. In mass spectrometry, detectors are the 'eyes' of the MS instrument. These 'eyes' have also been taken for granted. New detectors and new technologies are likewise needed to correct, improve, and extend ion detection and hence, our 'chemical vision'. The purpose of this report is to review and assess current MS detector technology and to provide a glimpse towards future detector technologies. It is hoped that the report will also serve to motivate interest, prompt ideas, and inspire new visions for ion detection research.
2004. "Foreword: Collision and reaction cell techniques in atomic mass spectrometry." Journal of Analytical Atomic Spectrometry 19(5):15N. Abstract This contribution is a guest editorial statement and technical assessment for a special issue of the Royal Society of Chemistry journal entitled Journal of Analytical Atomic Spectrometry (JAAS). The editorial introduces the subject area of collision and reaction cells in atomic mass spectrometry, reviews current literature and commercial instrumentation trends, and previews four perspective and numerous research articles contained in the special journal issue.
2004. "Collision and reaction cells in atomic mass spectrometry: development, status, and applications." Journal of Analytical Atomic Spectrometry 19(5):561-570. Abstract The development and utilization of collision and reaction cells in atomic mass spectrometry is reviewed. These devices have been used for decades in fundamental studies of ion-molecule chemistry and have only recently been applied in the GD-MS and ICP-MS fields. Such cells are used to promote reactive and non-reactive collisions, with resultant benefits in interference reduction, isobar separation, and thermalization/focusing of ions in ICP-MS. Novel ion-molecule chemistry schemes, using a variety of reaction gas reagents selected on the basis of thermodynamic and kinetic principles and data, are now designed and empirically evaluated with relative ease. These chemical resolution techniques can avert interferences requiring mass spectral resolutions of >600 000 (m/Δm). Purely physical ion beam processes, including collision dampening and collision dissociation, are also employed to provide improved sensitivity, resolution and spectral simplicity. Collision and reaction cell techniques are now firmly entrenched in current-day ICP-MS technology, enabling unprecedented flexibility and freedom from many spectral interferences. A significant body of applications has now been reported in the literature. Collision/reaction cell techniques are found to be most useful for specialized or difficult analytical needs and situations, and are employed in both single- and multi-element determination modes.
2004. "Use of a Novel Array Detector for the Direct Analysis of Solid Samples by Laser Ablation Inductively Coupled Plasma Sector-Field Mass Spectrometry." Journal of the American Society for Mass Spectrometry 15(6):769-776. Abstract A growing field of mass spectrometry research has been the development of novel array detectors capable of acquiring complete mass spectra in a simultaneous manner. Several benefits are realized through simultaneous detection, such as improved duty cycle, reduced analysis time and sample consumption, and the elimination of correlated noise through ratioing techniques. One such device, termed the focal plane camera (FPC), has recently been developed and fitted to a Mattauch-Herzog geometry mass spectrograph (MHMS).1 A key feature of the MHMS is the presence of a flat focal plane along which all m/z are focused simultaneously, allowing the use of a planar array detector. This instrument has been coupled with a laser ablation (LA) sampleintroduction system and inductively coupled plasma (ICP) ionization source. Laser ablation has several benefits: minimal sample preparation is necessary, it is applicable to many sample matrices, and it provides three dimensions of spatial resolution for analyte concentration. The combination of these techniques creates a powerful tool for solid-sample analysis.
2004. "Simultaneous multichannel mass-specific detention for high-performance liquid chromatography using an array detector sector-field mass spectrometer." Analytical and Bioanalytical Chemistry 380(2):227-234. Abstract Abstract The use of a separation step, such as liquid chromatography, prior to inductively coupled plasma mass spectrometry (ICP–MS) has become a common tool for highly selective and sensitive analyses. This type of coupling has several benefits including the ability to perform speciation analysis or to remove isobaric interferences. Several limitations of conventional instruments result from the necessity to scan or pulse the mass spectrometer to obtain a complete mass spectrum. When the instrument is operated in such a non-continuous manner, duty cycle is reduced, resulting in poorer absolute limits of detection. Additionally, with scanning instruments, spectral skew can be introduced into the measurement, limiting quantitation accuracy. To address these shortcomings, a high-performance liquid chromatograph has been coupled to an ICP–MS capable of continuous sample introduction and simultaneous multimass detection. These features have been realized with a novel detector array, the focal plane camera. Instrument performance has been tested for both speciation analysis and for the elimination of isobaric interferences. Absolute limits of detection in the sub picogram to tens of picograms regime are obtainable, while the added mass dimension introduced by simultaneous detection dramatically increases chromatographic peak capacity.
2004. "Coupling of a gas chromatograph to a simultaneous-detection inductively coupled plasma mass spectrograph for speciation of organohalide and organometallic compounds." Journal of Analytical Atomic Spectrometry 19(6):751-756. Abstract A gas chromatograph (GC) has been coupled to an inductively coupled plasma Mattauch-Herzog geometry mass spectrograph (ICP-MHMS) equipped with a novel detector array. In its current state of development the detector array, termed the focal plan camera (FPC), permits the simultaneous monitoring of up to 15 m/z values. A heated line was used to transfer the capillary-column effluent from the GC to the ICP torch, though due to instrument operating conditions, the transfer line was terminated 50 mm ahead of the ICP torch. Minimal tailing was observed, with the most severe effect seen for high-boiling analytes. With the coupling, absolute limits of detection are in the tens to hundreds of femtogram regime for organometallic species and in the single pictogram regime for halogenated hydrocarbons.
2004. "Characterization of a Focal Plane Camera Fittted to a Mattauch-Herzog Geometry Mass Spectrograph. 2. Use with an Inductively Coupled Plasma." Analytical Chemistry 76(9):2531-2536. Abstract A novel charge-sensitive detector array, termed the focal plane camera (FPC), has been coupled to a Mattauch-Herzog mass spectrograph (MHMS) with an inductively coupled plasma ionization source. The FPC employs an array of gold Faraday cups, each with its own chargeintegrating circuit that allows the simultaneous detection of several m/z ratios. The ion-sampling interface of the MHMS has been redesigned to provide better heat transfer away from the sampler and skimmer cones and to reduce the negative effects of turbulent gas flows around the plasma. The instrument has produced limits of detection in the tens to hundreds of parts per quadrillion regime and isotope ratio accuracy and precision of 5% error and 0.007% RSD, respectively. Limits of detection with the FPC are comparable to those obtained with a single-channel secondary electron multiplier (SEM). However, the isotope ratio accuracy and precision are better with the FPC than when the SEM is employed. The dynamic range has been shown to be linear over 7 orders of magnitude.
2003. "Development and characterization of an electrostatic quadrupole extraction lens for mass spectrometry." Journal of Analytical Atomic Spectrometry 18(9):1015-1018. Abstract In mass spectrometry, the majority of processes used to convert the analyte of interest into a detectable ion signal serve unfortunately also to reduce the detectable fraction of analyte. This lack of efficiency manifests itself in all aspects of mass spectrometry, from sample introduction to analyte detection. In atomic mass spectrometry, for example, techniqnes snch as pneumatic nebulization and laser ablation, which are nsed to convert samples from liquids or solids into particles, have efficiencies on the order of 1-10%. In both of these techniqnes, large particles are not readily transported to the ionization source, and therefore carry a large fraction of analyte to waste. Some modifications can improve efficiency, such as the use of high-efficiency nebulizers and more energetic lasers to produce smaller particles; however, complete transport is difficult to achieve.
2003. "A Mass Spectrometry Detector Array That Provides Truly Simultaneous Detection." American Laboratory 35(20):15-22. Abstract Over the nearly century-long existence of mass spectrometry, the technique has evolved from a researchlaboratory novelty to a well-characterized, widely employed method of analysis. With currently available technology, it is possible to dissect a sample and determine its composition, both qualitatively and quantitatively, in bulk and at trace levels, with a great deal of sensitivity and precision. However, the majority of recent advances in MS technology have focused on improving sample introduction methods and mass analyzer performance, with relatively little attention paid to ion detection.
2002. "The Development of a Micro-Faraday-Array for Ion Detection." International Journal of Mass Spectrometry and Ion Processes 215((1-3 SP ISS)):131-139. Abstract A micro-Faraday-array detector was evaluated for use as ion detector for mass spectrometry. This charge-integrating detector was based upon the merging of technologies from the fields of CCDs and infrared multiplexers. Measurements were performed by exposing the detector to an Ar+ ion beam of low flux. The array detector responds to both positive and negative charges and preliminary results indicate a detection limit of 100 ions. Current data indicate that the linear dynamic range of the device is over five orders of magnitude. The capability of the device to perform specialized charge read-out modes could theoretically both lower the detection limit by a factor of seven and increase the linear dynamic range to nine orders of magnitude using non-destructive read outs.
2002. "Evolution and Revolution in Instrumentation for Plasma-Source Mass Spectrometry ." Pure and Applied Chemistry 73(10):1579-1588. Abstract Plasma-source mass spectrometry, usually in the form of inductively coupled plasma mass spectrometry (ICP-MS), has matured into a widely accepted method for ultra-trace multielemental analysis. However, the method exhibits shortcomings. For example, it does not provide adequate precision for isotope ratio measurements if many isotopes are to be determined. Moreover, isobaric overlaps (spectral interferences) can be very troublesome in some situations. Similarly, matrix interferences can adversely affect many determinations. Yet, it is in the area of high-speed transient measurements that ICP-MS perhaps suffers its greatest weakness. When sampling devices such as flow injection, laser ablation, electrothermal vaporization, or chromatography are employed, the user must choose between broad elemental or isotopic coverage and signal-to-noise ratio (S/N). In turn, compromised S/N means lower precision or poorer detection limits. Here, new instrumentation aimed at overcoming these limitations will be described . One system, based on a time-of -flight mass spectrometer, provides excellent detection limits, resolving power better than commercial quadrupole mass filters, precision of at least 0.2% rsd in a ratioing mode, and extraordinarily high speed for use with transient sampling devices. The second instrument is based on a sector-field mass spectrometer but, unlike other such units, is equipped with a focal-plane array detector. So equipped, the system can detect a broad mass range at once.
2002. "Characterization of a Focal Plane Camera Fitted to a Mattauch-Herzog Geometry Mass Spectrograph. 1. Use with a Glow-Discharge Source." Analytical Chemistry 74(20):5327-5332. Abstract A Mattauch-Herzog geometry mass spectrograph (MHMS) has been equipped with a novel array detector, the focal plane camera (FPC). The FPC consists of an array of gold Faraday cups, each coupled to its own integrator, with interrogation of the integrators performed by a multi-plexer. The initial coupling of this instrument with a pin-type glow discharge source has provided limits of detection in the single to nanograms per gram regime; isotope ratio accuracy and precision better than 5% error and 0.2% RDS, respectively; and a linear dynamic range of at least 6 orders of magnitude. A current weakness of the FPC is its pixel size, which limits both sensitivity and baseline resolution (to R = 130). The minimum data acquisition time for multiple images at present is 1 ms/image, with a dead time of 3.2 ms between images, which will limit the ability of the FPC to monitor extremely short transient signals.
2001. "New advances in inductively coupled plasma-mass spectrometry (ICP-MS) for routine measurements in the nuclear industry." Journal of Radioanalytical and Nuclear Chemistry 249(1):103-108. Abstract Radioactive isotopes are traditionally quantified by means of radioactivity counting techniques (a, b ,y). These techniques often require extensive matrix separation and sample purification methods before unequivocal identification of specific isotopes and their relative abundance is possible. Counting times become very protracted when the half-life of the target analyte is very long or the concentration of the analyte is very low, e.g., environmental and bioassay measurement, which means that rapid response is difficult.
1999. "Actinides in Biological and Environmental Systems." Journal of Radioanalytical and Nuclear Chemistry 234:165-170.
1999. "Analytical Performance of the Plasma Source RF Quadrupole Ion Trap in Elemental and Isotopic MS." Journal of Analytical Atomic Spectrometry 14(8):1129-1132.