Analytical and Bioanalytical Chemistry (v.394, #1)
A light upon the horizon: young analytical chemists forging new scientific pathways during an economic downturn by Marc R. Knecht; Sylvia Daunert (1-3).
Meet the Guest Editors (5-6).
The ultimate “analytical challenge”: what is analytical chemistry? by Juris Meija (7-8).
is an assistant research officer at the Institute for National Measurement Standards, National Research Council Canada. His research interests encompass mathematical statistics, theoretical analytical chemistry, interpretation of isotope ratio measurement results, and the history of chemistry. He has recently been appointed Column Editor of the ABC Analytical Challenge series.
Mendeleyev vodka challenge by Juris Meija (9-10).
Solution to precision weighing challenge by Juris Meija (11-12).
Gene transfer and protein release of fission yeast by application of a high voltage electric pulse by Minoru Suga; Toyomasa Hatakeyama (13-16).
has been an Assistant Professor of the Graduate School of Science and Engineering at University of Toyama since April 2007. His current research interests include the development of methods for transformation of microorganisms by using electrical techniques. A high voltage electric pulse can be applied to induce the uptake of DNA into cells and the release of protein from cells. In transformation procedures, electroporation is widely used since the technique is simple, rapid, reproducible, and highly efficient. In extraction of protein, on the other hand, electroextraction has many advantages over other conventional extractions. We have developed a highly efficient method for the electroporation of fission yeast. In particular, application of a high voltage electric pulse to fission yeast improves the cellular uptake and release of macromolecules controlled by both osmotic conditions and electric field strength.
Keywords: Schizosaccharomyces pombe ; Electric field; Transformation; Electroporation; Electroextraction
Monitoring of vesicular exocytosis from single cells using micrometer and nanometer-sized electrochemical sensors by Wei Wang; Shu-Hui Zhang; Lin-Mei Li; Zong-Li Wang; Jie-Ke Cheng; Wei-Hua Huang (17-32).
is currently Professor in the College of Chemistry and Molecular Sciences at Wuhan University. His research interest includes electrochemical monitoring of chemical messengers released from single cells, and microfluidic-based systems for cell analysis. Communication between cells by release of specific chemical messengers via exocytosis plays crucial roles in biological process. Electrochemical detection based on ultramicroelectrodes (UMEs) has become one of the most powerful techniques in real-time monitoring of an extremely small number of released molecules during very short time scales, owing to its intrinsic advantages such as fast response, excellent sensitivity, and high spatiotemporal resolution. Great successes have been achieved in the use of UME methods to obtain quantitative and kinetic information about released chemical messengers and to reveal the molecular mechanism in vesicular exocytosis. In this paper, we review recent developments in monitoring exocytosis by use of UMEs-electrochemical-based techniques including electrochemical detection using micrometer and nanometer-sized sensors, scanning electrochemical microscopy (SECM), and UMEs implemented in lab-on-a-chip (LOC) microsystems. These advances are of great significance in obtaining a better understanding of vesicular exocytosis and chemical communications between cells, and will facilitate developments in many fields, including analytical chemistry, biological science, and medicine. Furthermore, future developments in electrochemical probing of exocytosis are also proposed. Figure In this paper, we review recent developments in monitoring the exocytosis by use of UMEs-electrochemical-based techniques including electrochemical detection using micrometer and nanometer-sized sensors, Scanning Electrochemical Microscopy (SECM) and UMEs implemented in lab-on-a-chip (LOC) microsystems. These advances are of great significance in obtaining a better understanding of vesicular exocytosis and chemical communications between cells, and will facilitate developments in many fields including analytical chemistry, biological science and medicine. Furthermore, future developments in electrochemical probing of exocytosis are proposed.
Keywords: Exocytosis; Micrometer and nanometer-sized electrochemical sensors; Scanning electrochemical microscopy; Microelectrode arrays; Lab-on-a-chip; Review
Bio-inspired colorimetric detection of Hg2+ and Pb2+ heavy metal ions using Au nanoparticles by Marc R. Knecht; Manish Sethi (33-46).
joined the Department of Chemistry at the University of Kentucky as an Assistant Professor in the Fall of 2007. His research is focused on the design and development of bio-inspired nanotechnologies using amino acids, peptides, and oligonucleotides for the fabrication of new materials. The applications for these materials range from biomineralization and nanomaterial self-assembly to green catalysis. Heavy metal ions are highly toxic species which can cause long-term damage to biological systems. These species are known to disrupt biological events at the cellular level, cause significant oxidative damage, and are carcinogens. The production of simple, in-field detection methods that are highly sensitive for these cations is highly desirable in response to global pollution. In that regard, bio-inspired colorimetric sensing systems have been developed to detect Hg2+ and Pb2+, and other cations, down to nmol L−1 concentrations. The benefits of these systems, which are reviewed herein, include cost-effective production, facile usage, and a visual color change for the detection method. Such advantages are significant positive steps for heavy metal ion detection, especially in regions where sophisticated laboratory studies are prohibited. Figure Biological-based colorimetric detection of heavy metal cations. The materials on the left are independent Au nanoparticles in solution, functionalized with heavy metal binding biomolecules, which, upon metal addition, aggregate to evolve a detectable solution color change.
Keywords: Bio-inspired nanotechnology; Colorimetric detection; Au nanoparticles; Heavy metal detection; Peptides; Oligonucleotides
Nanomaterials in fluorescence-based biosensing by Wenwan Zhong (47-59).
has been Assistant Professor of Chemistry at the University of California, Riverside, since July 2006. She received the Pilot Interdisciplinary Research Award from the Institute for Integrative Genome Biology of UC, Riverside. Her current research interests are: developing novel analytical strategies for utilizing nanomaterials in biosensing; studying nanotoxicity using microscale separation techniques like capillary electrophoresis; and developing field-flow fractionation-based methods for purification and analysis of large protein complexes. Fluorescence-based detection is the most common method utilized in biosensing because of its high sensitivity, simplicity, and diversity. In the era of nanotechnology, nanomaterials are starting to replace traditional organic dyes as detection labels because they offer superior optical properties, such as brighter fluorescence, wider selections of excitation and emission wavelengths, higher photostability, etc. Their size- or shape-controllable optical characteristics also facilitate the selection of diverse probes for higher assay throughput. Furthermore, the nanostructure can provide a solid support for sensing assays with multiple probe molecules attached to each nanostructure, simplifying assay design and increasing the labeling ratio for higher sensitivity. The current review summarizes the applications of nanomaterials—including quantum dots, metal nanoparticles, and silica nanoparticles—in biosensing using detection techniques such as fluorescence, fluorescence resonance energy transfer (FRET), fluorescence lifetime measurement, and multiphoton microscopy. The advantages nanomaterials bring to the field of biosensing are discussed. The review also points out the importance of analytical separations in the preparation of nanomaterials with fine optical and physical properties for biosensing. In conclusion, nanotechnology provides a great opportunity to analytical chemists to develop better sensing strategies, but also relies on modern analytical techniques to pave its way to practical applications.
Keywords: Nanomaterials; Quantum dots; Gold nanoparticle; Silica nanoparticle; Fluorescence; FRET; Biosensing
Magnetic microbead-based electrochemical immunoassays by Hideki Kuramitz (61-69).
is an Associate Professor of Environmental Science at University of Toyama. He received the Analytical Chemistry Award for Young Researchers of Chubu Region (Japan) in 2007. His current research areas include the development of new biochemical assays and water treatments based on electrochemical techniques, and assessment of environmental pollutants toxicity using microorganisms. This review provides a summary of recent works concerning electrochemical immunoassays using magnetic microbeads as a solid phase. Recent research activity has led to innovative and powerful detection strategies that have been resulted in sensitive electrochemical detection. Coupling of magnetic microbeads with highly sensitive electrochemical detection provides a useful analytical method for environmental evaluation and clinical diagnostics, etc. The huge surface area and high dispersion capability of magnetic microbeads strongly contributes towards the development of new sensitive, rapid, user-friendly, and miniaturized electrochemical immunoassay systems. Moreover, the immunocomplexes formed on the magnetic microbead surface can be easily detected without pretreatment steps such as preconcentration or purification, which are normally required for standard methods. The discussion in this review is organized in two main subjects that include magnetic-microbead-based assays using enzyme labels and nanoparticle tags. Figure SEM image of Dynabeads M-280 (12% γ-Fe2O3 in polystyrene, diameter is 2.8 μm)
Keywords: Electrochemical immunoassay; Magnetic microbead; Enzyme label; Nanoparticle tag
Recent advances in polymer monoliths for ion-exchange chromatography by Anna Nordborg; Emily F. Hilder (71-84).
has been a member of the Australian Centre for Research on Separation Science (ACROSS) at the University of Tasmania since 2004 where she held an ARC Australian Postdoctoral Fellowship from 2004–2007 and is currently Senior Lecturer and Coordinator for the research theme “Separation Materials”. Her current research focuses on the development of new separation media that can be used to improve the analysis of pharmaceutical and biological samples. She is also interested in miniaturised analytical systems, particularly for applications in biotechnology, clinical diagnostics, and counter-terrorism The use of polymeric materials in ion-exchange chromatography applications is advantageous because of their typically high mechanical stability and tolerance of a wide range of pH conditions. The possibility of using polymeric monoliths in ion-exchange chromatography is therefore obvious and many of the same strategies developed for polymeric particles have been adapted for use with polymeric monoliths. In this review different strategies for the synthesis of polymeric monoliths with ion-exchange functionality are discussed. The incorporation of ion-exchange functionality by co-polymerization is included, as also are different post-polymerization alterations to the monolith surface such as grafting. The formulations and strategies presented include materials intended for use in analytical separations in ion-exchange chromatography, sample pre-treatment or enrichment applications, and materials for capillary electrochromatography. Finally, examples of the use of polymeric monoliths in ion-exchange chromatography applications are included with examples published in the years 2003 to 2008.
Keywords: Polymeric monolith; Ion exchange; Co-polymerization; Surface modification; Coating; Grafting
Surface-enhanced Raman scattering (SERS) for probing internal cellular structure and dynamics by Katherine A. Willets (85-94).
is currently an assistant professor in the Department of Chemistry and Biochemistry at the University of Texas at Austin. She recently received an Air Force Young Investigator Award and has been recognized for her teaching at UT with the Natural Sciences Foundation Advisory Council Teaching Excellence Award. Dr. Willets’ current research interests include characterizing the enhanced electromagnetic fields of metal nanoparticles using sub-diffraction limited optical techniques and using surface-enhanced Raman scattering to characterize photo-induced structural changes in organic molecules. Surface-enhanced Raman scattering (SERS) provides vibrational information about molecules that are located within several nanometers of the surface of a metallic nanoparticle. This review describes the various challenges and successes of applying SERS inside living cells in order to gain information about the internal structure and dynamic processes occurring in the intracellular matrix. In particular, the challenges associated with the introduction of metal nanoparticles into cells are described, as well as the complexity of interpreting SERS spectra from within complex biological environments. Strategies for understanding and improving the specificity of SERS in vivo are also presented.
Keywords: Surface-enhanced Raman scattering (SERS); Cells; Nanoparticles
Electrochemical quantification of reactive oxygen and nitrogen: challenges and opportunities by Sabine Borgmann (95-105).
has been a scientist at Technische Universität Dortmund and ISAS—Institute for Analytical Sciences, Dortmund, in Germany since 2007. Her research interests are the development and implementation of new approaches to bioanalytical chemistry. The technologies involved are based on biochemical, (bio)electrochemical, and mass-spectrometric methods, with focus on miniaturization and automation. Reactive oxygen species (ROS) and reactive nitrogen species (RNS) play a crucial role in chemical signaling processes of biological cells. Electrochemistry is one of the rare methods able to directly detect these species. ROS and RNS can be monitored in the local microenvironment of cells in real time at the site where the actual signaling takes place. This review presents recent advances made with amperometric electrochemical techniques. Existing challenges for the quantification of ROS and RNS in biological systems are discussed to promote the development of innovative and reliable cell-based assays. Figure Reactive oxygen and nitrogen species (ROS & RNS) are produced biological cells. An amperometric sensor is placed in close proximity. The recorded current I is used to determine fluxes of certain species.
Keywords: Cell systems/single cell analysis; Electrochemical sensors; Bioanalytical methods; Reactive oxygen species; Reactive nitrogen species; Cell signaling
Principles of responsive lanthanide-based luminescent probes for cellular imaging by Aurore Thibon; Valérie C. Pierre (107-120).
started her independent career as an Assistant Professor at the University of Minnesota, Twin Cities in 2007. Her current research areas focuses on the development of responsive lanthanide based luminescent sensors for cellular imaging, and responsive MRI contrast agents for advanced in vivo diagnostics. The advent of chemical tools for cellular imaging—from organic dyes to green fluorescent proteins—has revolutionized the fields of molecular biology and biochemistry. Lanthanide-based probes are a new player in this area, as the last decade has seen the emergence of the first responsive luminescent lanthanide probes specifically intended for imaging cellular processes. The potential of these probes is still undervalued by the scientific community. Indeed, this class of probes offers several advantages over organic dyes and fluorescent proteins. Their very long luminescence lifetimes enable quantitative spatial determination of the intracellular concentration of an analyte through time-gating measurements. Their emission bands are very narrow and do not overlap, enabling the simultaneous use of multiple lanthanide probes to quantitatively detect several analytes without cross-interference. Herein we describe the principles behind the development of this class of probes. Sensors for a desired analyte can be designed by rationally manipulating the parameters that influence the luminescence of lanthanide complexes. We will discuss sensors based on varying the number of inner-sphere water molecules, the distance separating the antenna from the lanthanide ion, the energies of excited states of the antenna, and PeT switches.
Keywords: Lanthanide luminescence; Sensors; Cellular probes; Time-gated detection; Sensitized emission; Photoelectron transfer
Label-free technologies for quantitative multiparameter biological analysis by Abraham J. Qavi; Adam L. Washburn; Ji-Yeon Byeon; Ryan C. Bailey (121-135).
is an Assistant Professor of Chemistry at the University of Illinois at Urbana-Champaign and an affiliate in the university’s Institute for Genomic Biology. He won a 2006 Camille and Henry Dreyfus Foundation New Faculty Award and was the recipient of an inaugural US National Institutes of Health Director’s New Innovator Award in 2007. His group is developing new multiparameter biological analysis technologies based upon high-density optical biosensor arrays and novel surface patterning strategies. In the postgenomic era, information is king and information-rich technologies are critically important drivers in both fundamental biology and medicine. It is now known that single-parameter measurements provide only limited detail and that quantitation of multiple biomolecular signatures can more fully illuminate complex biological function. Label-free technologies have recently attracted significant interest for sensitive and quantitative multiparameter analysis of biological systems. There are several different classes of label-free sensors that are currently being developed both in academia and in industry. In this critical review, we highlight, compare, and contrast some of the more promising approaches. We describe the fundamental principles of these different methods and discuss advantages and disadvantages that might potentially help one in selecting the appropriate technology for a given bioanalytical application.
Keywords: Genomics/proteomics; Bioassays; Biochips/high-throughput screening; Biosensors; Clinical/biomedical analysis; Immunoassays/ELISA
Environmental metabolomics: new insights into earthworm ecotoxicity and contaminant bioavailability in soil by Myrna J. Simpson; Jennifer R. McKelvie (137-149).
is an Associate Professor of Environmental Chemistry and the Associate Director of the Environmental NMR Centre at the University of Toronto. She is the recipient of a NSERC University Faculty Award, a Province of Ontario Premier’s Research Excellence Award, and a UofT Principal’s Research Award. Her current research interests include the development and application of analytical methods for the study of environmental processes. Environmental metabolomics is a growing and emerging sub-discipline of metabolomics. Studies with earthworms have progressed from the initial stages of simple contact exposure tests to detailed studies of earthworm responses in soil. Over the past decade, a variety of endogenous metabolites have been identified as potential biomarkers of contaminant exposure. Furthermore, metabolomic methods have delineated responses from sub-lethal exposure of earthworms to polycyclic aromatic hydrocarbons and metals in soil suggesting that environmental metabolomics may be used as a direct measure of contaminant bioavailability in soil. Environmental metabolomics has the potential to fill knowledge gaps related to earthworm toxicity and contaminant bioavailability. However, challenges with metabolite quantification and limited systems-level models of metabolic data require improvement before detailed models of “normal” responses can be developed and used routinely in assessment of contaminated sites. Nonetheless, environmental metabolomics is poised to improve our fundamental understanding of earthworm responses and toxicity to contaminants in soil. Figure Principal component analysis (PCA) scores plots of earthworm metabolic profiles measured by 1H NMR spectroscopy after exposure to sub-lethal concentrations of phenanthrene in soil.
Keywords: 1H NMR; Metabolic profiling; Metabonomics; Soil contamination; Bioaccessibility
The correspondence problem for metabonomics datasets by K. Magnus Åberg; Erik Alm; Ralf J. O. Torgrip (151-162).
holds a Ph.D. in chemometrics and has been a researcher in the BioSysteMetrics Group at the Department of Analytical Chemistry at Stockholm University since 2006. His current research interests are developing algorithms and methods for maximizing information recovery from data, e.g. from metabonomics In metabonomics it is difficult to tell which peak is which in datasets with many samples. This is known as the correspondence problem. Data from different samples are not synchronised, i.e., the peak from one metabolite does not appear in exactly the same place in all samples. For datasets with many samples, this problem is nontrivial, because each sample contains hundreds to thousands of peaks that shift and are identified ambiguously. Statistical analysis of the data assumes that peaks from one metabolite are found in one column of a data table. For every error in the data table, the statistical analysis loses power and the risk of missing a biomarker increases. It is therefore important to solve the correspondence problem by synchronising samples and there is no method that solves it once and for all. In this review, we analyse the correspondence problem, discuss current state-of-the-art methods for synchronising samples, and predict the properties of future methods.
Keywords: Alignment; Warping; Chromatography; Metabolic profiling; NMR; Mass spectrometry (MS)
Oligosaccharide analysis by graphitized carbon liquid chromatography–mass spectrometry by L. Renee Ruhaak; André M. Deelder; Manfred Wuhrer (163-174).
is Associate Professor at the Biomolecular Mass Spectrometry Unit, Leiden University Medical Center, and is leading the Glycomics and Glycoproteomics group. His research comprises high-throughput glycosylation profiling, tandem mass spectrometry for structure elucidation, and use of natural glycan microarrays for studying protein–carbohydrate interactions at ultrahigh sensitivity. Structural analysis of complex mixtures of oligosaccharides using tandem mass spectrometry is regularly complicated by the presence of a multitude of structural isomers. Detailed structural analysis is, therefore, often achieved by combining oligosaccharide separation by HPLC with online electrospray ionization and mass spectrometric detection. A very popular and promising method for analysis of oligosaccharides, which is covered by this review, is graphitized carbon HPLC–ESI-MS. The oligosaccharides may be applied in native or reduced form, after labeling with a fluorescent tag, or in the permethylated form. Elution can be accomplished by aqueous organic solvent mixtures containing low concentrations of acids or volatile buffers; this enables online ESI-MS analysis in positive-ion or negative-ion mode. Importantly, graphitized carbon HPLC is often able to resolve many glycan isomers, which may then be analyzed individually by tandem mass spectrometry for structure elucidation. While graphitized carbon HPLC–MS for glycan analysis is still only applied by a limited number of groups, more users are expected to apply this method when databases which support structural assignment become available.
Keywords: Glycan; Graphitized carbon; Mass spectrometry
Sweeping and new on-line sample preconcentration techniques in capillary electrophoresis by Agnes T. Aranas; Armando M. Guidote Jr.; Joselito P. Quirino (175-185).
was appointed Senior Lecturer and Research Fellow at the Australian Centre for Research on Separation Science, Department of Chemistry at the University of Tasmania, Australia in December 2007. His research is focused on the fundamentals and applications of capillary electrophoresis. Sweeping is a powerful on-line sample preconcentration technique that improves the concentration sensitivity of capillary electrophoresis (CE). This approach is designed to focus the analyte into narrow bands within the capillary, thereby increasing the sample volume that can be injected, without any loss of CE efficiency. It utilizes the interactions between an additive [i.e., a pseudostationary phase (PS) or complexing agent] in the separation buffer and the sample in a matrix that is devoid of the additive used. The accumulation occurs due to chromatographic partitioning, complexation or any interaction between analytes and the additive through electrophoresis. The extent of the preconcentration is dependent on the strength of interaction involved. Both charged and neutral analytes can be preconcentrated. Remarkable improvements—up to several thousandfold—in detection sensitivity have been achieved. This suggests that sweeping is a superior and general approach to on-line sample preconcentration in CE. The focusing mechanism of sweeping under different experimental conditions and its combination with other on-line preconcentration techniques are discussed in this review. The recently introduced techniques of transient trapping (tr-trapping) and analyte focusing by micelle collapse (AFMC) as well as other novel approaches to on-line sample preconcentration are also described.
Keywords: On-line sample preconcentration; Sweeping; Sample stacking; Analyte focusing by micelle collapse; Capillary electrophoresis
Micro free-flow electrophoresis: theory and applications by Ryan T. Turgeon; Michael T. Bowser (187-198).
is currently an Associate Professor at the University of Minnesota where he has been a faculty member in the Department of Chemistry since 2000. Michael was the 2005 recipient of the ACS Award for Young Investigators in Separation Science. His research interests include microfluidic devices, high-speed neurotransmitter measurements and techniques for isolating high-affinity aptamers. Free-flow electrophoresis (FFE) is a technique that performs an electrophoretic separation on a continuous stream of analyte as it flows through a planar flow channel. The electric field is applied perpendicularly to the flow to deflect analytes laterally according to their mobility as they flow through the separation channel. Miniaturization of FFE (μFFE) over the past 15 years has allowed analytical and preparative separation of small volume samples. Advances in chip design have improved separations by reducing interference from bubbles generated by electrolysis. Mechanisms of band broadening have been examined theoretically and experimentally to improve resolution in μFFE. Separations using various modes such as zone electrophoresis, isoelectric focusing, isotachophoresis, and field-step electrophoresis have been demonstrated.
Keywords: Electrophoresis; Microfluidics; Free-flow electrophoresis
Isotope scrambling and error magnification in multiple-spiking isotope dilution by Juris Meija; Laurent Ouerdane; Zoltán Mester (199-205).
is an Assistant Research Officer at the Institute for National Measurement Standards, National Research Council Canada. Among many honors, his most cherished to date is the one-hour interview by the Latvian State Radio pertaining to his expertise in classical music. His research interests encompass mathematical statistics, mass spectrometry data analysis, interpretation of isotope ratio measurement results and history of chemistry. The purpose of performing multiple spiking isotope dilution is to quantify interconverting substances. This feature has been utilized in analytical chemistry now for more than a decade. In this manuscript we show that the interconversion of analytes is inevitably accompanied by the gradual loss of information that can be extracted from the isotope patterns. Therefore, any corrections for analyte interconversion are performed at the expense of the precision of the obtained amount of interconverting analytes. Consequently, there is a natural, predictable limit to the applicability of multiple-spiking isotope dilution methods that can be summarized into a simple equation.
Keywords: Isotope dilution; Multiple spiking; Uncertainty; Error propagation; Monte Carlo; Isotope scrambling
Label-free detection of the aptamer binding on protein patterns using Kelvin probe force microscopy (KPFM) by Pei Gao; Yuguang Cai (207-214).
is an Assistant Professor in the Department of Chemistry, University of Kentucky. He graduated from Peking University, China with a B.S. degree. He received the Ph.D. degree in chemistry from Princeton University in 2003. After finishing his post-doctoral training in the Physics Department of Brookhaven National Laboratory, he joined University of Kentucky in 2006. His research interests include surface patterning, pattern-directed assembly process, and the liquid spreading over textured surfaces at nanoscale. Anti-lysozyme aptamers are found to preferentially bind to the edge of a tightly packed lysozyme pattern. Such edge-binding is due to the better accessibility and flexibility of the edge lysozyme molecules. Kelvin probe force microscopy (KPFM) was used to study the aptamer–lysozyme binding. Our results show that KPFM is capable of detecting the aptamer–protein binding down to the 30 nm scale. The surface potential of the aptamer–lysozyme complex is approximately 12 mV lower than that of the lysozyme. The surface potential images of the aptamer-bound lysozyme patterns have the characteristic shoulder steps around the pattern edge, which is much wider than that of a clean lysozyme pattern. These results demonstrate the potentials of KPFM as a label-free method for the detection of protein–DNA interactions. Figure Aptamers preferentially bind on the edge of a protein pattern as revealed by Kelvin force microscopy.
Keywords: AFM (atomic force microscopy); Bioanalytical methods; Interface/surface analysis; Thin films
Investigation of the magnetic properties of ferritin by AFM imaging with magnetic sample modulation by Stephanie L. Daniels; Johnpeter N. Ngunjiri; Jayne C. Garno (215-223).
has been an Assistant Professor of Chemistry at Louisiana State University since August 2004. She was awarded an NRC post-doctoral fellowship at NIST in 2003. She won a Ralph E. Powe Junior Faculty Enhancement Award in 2005 from Oak Ridge Associated Universities and was awarded a National Science Foundation Early Career Award for 2009–2014. Her research applies scanning probe microscopy for molecular-level investigations of biochemical surface reactions. Individual ferritin molecules can be sensitively detected using magnetic sample modulation (MSM) combined with contact mode atomic force microscopy (AFM). To generate an oscillating magnetic field, an alternating current (AC) was applied to a solenoid placed within the base of the AFM sample stage. When a modulated electromagnetic field is applied to samples, ferromagnetic and paramagnetic nanomaterials are induced to vibrate. The flux of the AC electromagnetic field causes the ferritin samples to vibrate with corresponding rhythm and periodicity of the applied field. This motion can be detected and mapped using contact mode AFM with a soft, nonmagnetic cantilever. Changes in the phase and amplitude of the periodic motion of the sample are sensed by the tip to selectively map vibrating magnetic nanomaterials. Particle lithography was used to create nanopatterned test platforms of ferritin for MSM measurements. Regularly spaced structures of proteins provide precise reproducible dimensions for multiple successive surface measurements at dimensions of tens of nanometers. Figure Ring patterns of ferritin were used as nanoscale test platforms to characterize magnetic properties at the level of individual proteins with AFM imaging
Keywords: Ferritin; Magnetic sample modulation; Superparamagnetic; Nanomagnetism; AFM; Protein nanopatterns
Measurement of longitudinal sulfur isotopic variations by laser ablation MC-ICP-MS in single human hair strands by Rebeca Santamaria-Fernandez; Justo Giner Martínez-Sierra; J. M. Marchante-Gayón; J. Ignacio García-Alonso; Ruth Hearn (225-233).
joined LGC in 2005 and is now a Senior Researcher in Isotope Ratio Mass Spectrometry at LGC in Teddington, UK. In 2007, she won the Allan Ure Award for her contribution to the application of atomic spectrometry to environmental science. Her current research interests focus on the development of new methodologies involving traceable high-precision isotope ratio measurements using IRMS and multicollector ICP-MS technologies. A new method for the measurement of longitudinal variations of sulfur isotope amount ratios in single hair strands using a laser ablation system coupled to a multicollector inductively coupled plasma mass spectrometer (LA-MC-ICP-MS) is reported here for the first time. Ablation parameters have been optimized for the measurement of sulfur isotope ratios in scalp human hair strands of 80–120-μm thickness and different washing procedures have been evaluated. The repeatability of the method has been tested and the ability to measure sulfur isotopic variations in 1,000-μm-long hair segments has been evaluated. A horse hair sample previously characterized for carbon and nitrogen isotope ratios in an interlaboratory study has been characterized by LA-MC-ICP-MS to be used as an in-house standard for the bracketing of human hair strands. 34S/32S isotope amount ratios have been measured and corrected for instrumental mass bias adopting the external standardization approach using National Institute of Standards and Technology (NIST) RM8553 and full uncertainty budgets have been calculated using the Kragten approach. Results are reported as both 34S/32S isotope amount ratios and δSV-CDT values (sulfur isotopic differences relative to a reference sample expressed in the Vienna Canyon Diablo Troilite (V-CDT) scale) calculated using NIST RM8553, NIST RM8554, and NIST RM8556 to anchor results to the V-CDT scale. The main advantage of the new method versus conventional gas source isotope ratio mass spectrometry measurements is that longitudinal variations in sulfur isotope amount ratios can be resolved. Proof of concept is shown with human scalp hair strands from three individuals, two UK residents and one traveler (long periods of time abroad). The method enables monitoring of longitudinal isotope ratio variations in single hair strands. Absolute ratios are reported and δ34SV-CDT values are plotted for comparison. Slight variations of <1.2‰ were detected in the hair strands from UK residents whereas the traveler presented a variation of >5‰. Thus, the measurement of sulfur isotopic variations in hair samples has potential to be an indicator of geographical origin and recent movements and could be used in combination with isotope ratio measurements in water/foodstuffs from different geographical locations to provide important information in nutritional and geographical studies. Figure The measurement of longitudinal sulfur isotopic variations by LA-MC-ICP-MS in single human hair strands could play an important role in human identification providing information regarding geographical origin, recent movements and lifestyle of an individual
Keywords: Mass spectrometry/ICP-MS; Laser ablation; Forensics; Sulfur; Isotope ratio; MC-ICP-MS
Characterizing ion mobility-mass spectrometry conformation space for the analysis of complex biological samples by Larissa S. Fenn; Michal Kliman; Ablatt Mahsut; Sophie R. Zhao; John A. McLean (235-244).
is presently an Assistant Professor in the Department of Chemistry at Vanderbilt University and a faculty fellow in the Institute of Chemical Biology and Institute of Integrative Biosystems Research and Education. His recent awards include an American Society for Mass Spectrometry Research Award, a Spectroscopy Society of Pittsburgh Award, an R&D 100 Award, and the Bunsen–Kirchhoff Prize from the GDCh. His research interests focus on the design, conceptualization, construction, and application of technologies for structural mass spectrometry, in particular for studies in structural proteomics, systems biology, and biophysics. The conformation space occupied by different classes of biomolecules measured by ion mobility-mass spectrometry (IM-MS) is described for utility in the characterization of complex biological samples. Although the qualitative separation of different classes of biomolecules on the basis of structure or collision cross section is known, there is relatively little quantitative cross-section information available for species apart from peptides. In this report, collision cross sections are measured for a large suite of biologically salient species, including oligonucleotides (n = 96), carbohydrates (n = 192), and lipids (n = 53), which are compared to reported values for peptides (n = 610). In general, signals for each class are highly correlated, and at a given mass, these correlations result in predicted collision cross sections that increase in the order oligonucleotides < carbohydrates < peptides < lipids. The specific correlations are described by logarithmic regressions, which best approximate the theoretical trend of increasing collision cross section as a function of increasing mass. A statistical treatment of the signals observed within each molecular class suggests that the breadth of conformation space occupied by each class increases in the order lipids < oligonucleotides < peptides < carbohydrates. The utility of conformation space analysis in the direct analysis of complex biological samples is described, both in the context of qualitative molecular class identification and in fine structure examination within a class. The latter is demonstrated in IM-MS separations of isobaric oligonucleotides, which are interpreted by molecular dynamics simulations. Figure Potential for performing simultaneous “omics” through the separation of biomolecular classes on the basis of structure and mass using ion mobility-mass spectrometry
Keywords: Ion mobility; Ion mobility-mass spectrometry; Mass spectrometry; Collision cross section; Conformation space; Oligonucleotides; Carbohydrates; Peptides; Lipids
Reactive desorption electrospray ionization mass spectrometry (DESI-MS) of natural products of a marine alga by Leonard Nyadong; Edward G. Hohenstein; Asiri Galhena; Amy L. Lane; Julia Kubanek; C. David Sherrill; Facundo M. Fernández (245-254).
has been an Assistant Professor of Chemistry at the Georgia Institute of Technology since January 2004. He has recently won the NSF CAREER award, ASMS Research award, SACP Starter Grant award, and the 3M Non-tenured Faculty Grant award. His current research interests include the study and development of new ionization methods for analytical mass spectrometry, mass spectrometry imaging, and ion mobility gas-phase separations. He is also interested in the application of these technologies to metabolomics. Presented here is the optimization and development of a desorption electrospray ionization mass spectrometry (DESI-MS) method for detecting natural products on tissue surfaces. Bromophycolides are algal diterpene-benzoate macrolide natural products that have been shown to inhibit growth of the marine fungal pathogen Lindra thalassiae. As such, they have been implicated in antimicrobial chemical defense. However, the defense mechanisms are not yet completely understood. Precise detection of these compounds on algal tissue surfaces under ambient conditions without any disruptive sample processing could shed more light onto the processes involved in chemical defense of marine organisms. Conventional DESI-MS directly on algal tissue showed relatively low sensitivity for bromophycolide detection. Sensitivity was greatly improved by the addition of various anions including Cl−, Br−, and CF3COO− into the DESI spray solvent. Chloride adduction gave the highest sensitivity for all assayed anions. Density functional optimization of the bromophycolide anionic complexes produced during DESI supported this observation by showing that the chloride complex has the most favorable binding energy. Optimized DESI protocols allowed the direct and unambiguous detection of bromophycolides, including A, B, and E, from the surface of untreated algal tissue. Figure Desorption Electrospray Ionization, a novel technique for mass spectrometric analysis under open air conditions reveals the presence of naturally-occurring antibiotics on the surface of marine algae. Ab-initio calculations and experimental results indicate that sensitiviity could be greatly enhanced by means of dynamic complexation of these antibiotics with various small anions during the dynamic desorption process.
Keywords: Desorption electrospray ionization; Mass spectrometry; Direct analysis; Natural products
Evaluation of polyurethane foam, polypropylene, quartz fiber, and cellulose substrates for multi-element analysis of atmospheric particulate matter by ICP-MS by Nabin Upadhyay; Brian J. Majestic; Panjai Prapaipong; Pierre Herckes (255-266).
is currently an Assistant Professor at the Arizona State University in the Department of Chemistry and Biochemistry. His research interests are in environmental analytical chemistry with applications in atmospheric chemistry, in particular cloud and aerosol chemistry and cloud/aerosol interactions. Traditional methods for the analysis of trace metals require particulate matter (PM) collected on specific filter substrates. In this paper, methods for elemental analysis of PM collected on substrates commonly used for organic analysis in air quality studies are developed. Polyurethane foam (PUF), polypropylene (PP), and quartz fiber (QF) substrates were first digested in a mixture of HNO3/HCl/HF/H2O2 using a microwave digestion system and then analyzed for elements by inductively coupled plasma mass spectrometry. Filter blanks and recoveries for standard reference materials (SRMs) on these substrates were compared with a cellulose (CL) substrate, more commonly used for trace metal analysis in PM. The results show concentrations of filter blanks in the order of QF > PUF > PP > CL with a high variability in PUF and PP blanks relative to QF. Percent recovery of most elements from the SRMs on all substrates are within ±20% of certified or reference values. QF substrates showed consistent blanks with a reproducibility better than ±10% for the majority of elements. Therefore, QF substrates were applied to ambient PM collected in a variety of environments from pristine to polluted. Concentrations of field blanks for ≥18 of 31 elements analyzed on a small section of QF substrate are ≤25% of the amounts present in samples for urban atmospheres. Results suggest that QF used in a high-volume sampler can be a suitable substrate to quantify trace elements, in addition to organic species and hence reduce logistics and costs in air pollution studies.
Keywords: Particulate matter; Atmospheric aerosol; ICP-MS; Trace metals; Air pollution
Complementary precursor ion and neutral loss scan mode tandem mass spectrometry for the analysis of glycerophosphatidylethanolamine lipids from whole rat retina by Todd A. Lydic; Julia V. Busik; Walter J. Esselman; Gavin E. Reid (267-275).
has been an Assistant Professor in the Department of Chemistry and the Department of Biochemistry and Molecular Biology at Michigan State University since 2004. He received a National Science Foundation CAREER Award in 2006 and an American Society for Mass Spectrometry Research Award in 2007. His research interests include fundamental and applied studies toward the development of improved mass spectrometry methods for proteome and lipidome analysis. A “shotgun” tandem mass spectrometry (MS) approach involving the use of multiple lipid-class-specific precursor ion and neutral loss scan mode experiments has been employed to identify and characterize the glycerophosphatidylethanolamine (GPEtn) lipids that were present within a crude lipid extract of a normal rat retina, obtained with minimal sample handling prior to analysis. Characterization of these lipids was performed by complementary analysis of their protonated and deprotonated precursor ions, as well as their various ionic adducts (e.g., Na+, Cl-), using a triple-quadrupole mass spectrometer. Notably, the application of novel precursor ion and neutral loss scans of m/z 164 and m/z 43, respectively, for the specific identification of sodiated GPEtn precursor ions following the addition of 500 μM NaCl to the crude lipid extracts was demonstrated. The use of these novel MS/MS scans in parallel provided simplified MS/MS spectra and enhanced the detection of 1-alkenyl, 2-acyl (plasmenyl) GPEtn lipids relative to the positive ion mode neutral loss m/z 141 commonly used for GPEtn analysis. Furthermore, the novel use of a “low energy” neutral loss scan mode experiment to monitor for the exclusive loss of 36m/z (HCl) from [M+Cl]- GPEtn adducts was demonstrated to provide a more than 25-fold enhancement for the detection of GPEtn lipids in negative ion mode analysis. Subsequent “high-energy” pseudo MS3 product ion scans on the precursor ions identified from this experiment were then employed to rapidly characterize the fatty acyl chain substituents of the GPEtn lipids.
Keywords: Retina; Lipidomics; Glycerophosphatidylethanolamine; Electrospray ionization; Tandem mass spectrometry
Cell separation by the combination of microfluidics and optical trapping force on a microchip by Masaya Murata; Yukihiro Okamoto; Yeon-Su Park; Noritada Kaji; Manabu Tokeshi; Yoshinobu Baba (277-283).
has been an Assistant Professor at Nagoya University since April 2008. His current research interests are the development of functional materials and their application to high-performance biomolecule analysis. We investigated properties of cells affecting their optical trapping force and successfully established a novel cell separation method based on the combined use of optical trapping force and microfluidics on a microchip. Our investigations reveal that the morphology, size, light absorption, and refractive index of cells are important factors affecting their optical trapping force. A sheath flow of sample solutions created in a microchip made sample cells flow in a narrow linear stream and an optical trap created by a highly focused laser beam captured only target cells and altered their trajectory, resulting in high-efficiency cell separation. An optimum balance between optical trapping force and sample flow rate was essential to achieve high cell separation efficiency. Our investigations clearly indicate that the on-chip optical trapping method allows high-efficiency cell separation without cumbersome and time-consuming cell pretreatments. In addition, our on-chip optical trapping method requires small amounts of sample and may permit high-throughput cell separation and integration of other functions on microchips. Figure Optical trapping in a microchannel allows high-efficiency separation of cells, e.g., dead and live HeLa cells
Keywords: Optical trapping; Microchip; Cell separation; Sheath flow; Trapping force
Shape selectivity in embedded polar group stationary phases for liquid chromatography by Catherine A. Rimmer; Lane C. Sander (285-291).
is a Research Chemist at the National Institute of Standards and Technology where she began as a National Research Council Postdoctoral Fellow. Her research efforts are currently directed towards an improved understanding of chromatographic processes to advance the “state of the art” in chemical metrology. Seven columns with embedded polar functionality were evaluated for use in liquid chromatography with a focus on molecular shape recognition. Tests based on Standard Reference Material 869b Column Selectivity Test Mixture for Liquid Chromatography and the Tanaka test indicate that only two of the phases are slightly shape selective at 20 °C. The shape recognition characteristics of the phases appear to be directly related to the density of the embedded polar ligands and the temperature of the separation, consistent with trends observed with conventional hydrocarbon phases.
Keywords: Liquid chromatography; Shape selectivity; Embedded polar group
Characterization of electrokinetic mobility of microparticles in order to improve dielectrophoretic concentration by José I. Martínez-López; Héctor Moncada-Hernández; Javier L. Baylon-Cardiel; Sergio O. Martínez-Chapa; Marco Rito-Palomares; Blanca H. Lapizco-Encinas (293-302).
has been an Assistant Professor of Biotechnology at Tecnológico de Monterrey, Mexico, since 2005, and was promoted to Associate Professor in 2009. She received the 2008 UNESCO-L’OREAL Award For Women in Science in Mexico. Her current research interests are microscale bioseparations with focus on electrophoresis and dielectrophoresis. Insulator-based dielectrophoresis (iDEP), an efficient technique with great potential for miniaturization, has been successfully applied for the manipulation of a wide variety of bioparticles. When iDEP is applied employing direct current (DC) electric fields, other electrokinetic transport mechanisms are present: electrophoresis and electroosmotic flow. In order to concentrate particles, iDEP has to overcome electrokinetics. This study presents the characterization of electrokinetic flow under the operating conditions employed with iDEP; in order to identify the optimal conditions for particle concentration employing DC-iDEP, microparticle image velocimetry (μPIV) was employed to measure the velocity of 1-μm-diameter inert polystyrene particles suspended inside a microchannel made from glass. Experiments were carried out by varying the properties of the suspending medium (conductivity from 25 to 100 μS/cm and pH from 6 to 9) and the strength of the applied electric field (50–300 V/cm); the velocities values obtained ranged from 100 to 700 μm/s. These showed that higher conductivity and lower pH values for the suspending medium produced the lowest electrokinetic flow, improving iDEP concentration of particles, which decreases voltage requirements. These ideal conditions for iDEP trapping (pH = 6 and σ m = 100 μS/cm) were tested experimentally and with the aid of mathematical modeling. The μPIV measurements allowed obtaining values for the electrokinetic mobilities of the particles and the zeta potential of the glass surface; these values were used with a mathematical model built with COMSOL Multiphysics software in order to predict the dielectrophoretic and electrokinetic forces exerted on the particles; the modeling results confirmed the μPIV findings. Experiments with iDEP were carried out employing the same microparticles and a glass microchannel that contained an array of cylindrical insulating structures. By applying DC electric fields across the insulating structures array, it was seen that the dielectrophoretic trapping was improved when the electrokinetic force was the lowest; as predicted by μPIV measurements and the mathematical model. The results of this study provide guidelines for the selection of optimal operating conditions for improving insulator-based dielectrophoretic separations and have the potential to be extended to bioparticle applications. Figure Comparison of experimental measurements and mathematical modeling of electrokinetic and dielectrophoretic effects on microparticles
Keywords: Electrokinetic; Electroosmosis; Dielectrophoresis; Microfluidics; μPIV; Microchannel
Partition layer-modified substrates for reversible surface-enhanced Raman scattering detection of polycyclic aromatic hydrocarbons by Courtney L. Jones; Kyle C. Bantz; Christy L. Haynes (303-311).
is currently a McKnight Land-Grant Assistant Professor of Chemistry at the University of Minnesota in Minneapolis. In 2006, Haynes was named a Kinship Foundation Searle Scholar, and in 2008, she was chosen as a National Institutes of Health New Innovator. The Haynes group research activities include developing electrochemical assays to monitor nanoparticle toxicity, exploring how immune cells communicate with one another at the single cell level, and developing surface-enhanced Raman scattering chemosensors. Herein, we present progress towards an analytical sensor for polycyclic aromatic hydrocarbons (PAHs) using surface-enhanced Raman scattering (SERS) on partition layer-modified nanostructured substrates. Specifically, a 1-decanethiol monolayer has been assembled on a silver film over nanospheres substrate to concentrate PAHs within the zone of SERS detection. Both anthracene and pyrene were detected with limits of detection at 300 and 700 pM, respectively. The measured SERS spectra allowed for easy distinction of the two PAH compounds, due to varying peak locations, and insight into the partitioning mechanism. Additionally, exposure to a common environmental interferant, Suwannee River fulvic acid, did not impede the measurement of the PAHs, and the sensor is reusable after a short exposure to 1-octanol. Finally, the utility of this sensing platform for PAH detection was compared to that achievable for other classes of organic pollutants such as polychlorinated biphenyls and polybrominated diphenyl ethers. Figure SERS detection of polycyclic aromatic hydrocarbons facilitated via partition layer modified substrates.
Keywords: Surface-enhanced Raman scattering; Polycyclic aromatic hydrocarbons; Chemosensor; Partition layer
Optimization of capillary electrophoresis conditions for a glucagon competitive immunoassay using response surface methodology by Anna R. Lomasney; Christelle Guillo; Ashley M. Sidebottom; Michael G. Roper (313-319).
has been an Assistant Professor of Chemistry at Florida State University since August 2006. His current research interests are in the development of bioanalytical methods for measuring cellular signaling and secretory processes. The capillary electrophoresis (CE) conditions for a competitive immunoassay of glucagon were optimized for highest sensitivity of the immunoassay and resolution of the electrophoretic peaks using a Box–Behnken design. Injection time, voltage ramp time, and separation voltage were varied between three levels and two responses, bound-to-free (B/F) ratio of the immunoassay peaks and resolution between the peaks, were measured. Analysis of variance was applied to fit a predictive model, and a desirability function was used to simultaneously optimize both responses. A 10-s injection, 1.6-min ramp time, and a 22-kV separation voltage were the conditions found when high B/F was given more emphasis than high resolution. To test the model, calibration curves of a glucagon immunoassay were measured at the optimum and least optimum CE conditions. Optimal conditions increased the sensitivity of the immunoassay by 388% compared to the least optimum conditions while maintaining adequate resolution.
Keywords: CE; Response surface methodology; Optimization; Glucagon; Competitive immunoassay
A fluorous tag-bound fluorescence derivatization reagent, F-trap pyrene, for reagent peak-free HPLC analysis of aliphatic amines by Kenichiro Todoroki; Hidemichi Etoh; Hideyuki Yoshida; Hitoshi Nohta; Masatoshi Yamaguchi (321-327).
is Research Associate in the Department of Analytical Chemistry, Faculty of Pharmaceutical Sciences at Fukuoka University (Japan). His research interests are in the development of novel biomedical analytical methods based on a unique fluorescent probe, HPLC, fluorous chemistry, metabolomics, and fluorescence interactions (FRET, exciplex, excimer). We have developed a novel pre-column fluorescence derivatization reagent for amines, F-trap pyrene. This reagent comprises a fluorescent pyrene moiety, an amine-reactive Marshall linker, and a fluorophilic perfluoroalkyl group known as fluorous tag. When the reagent reacts with aliphatic amines and amino acids to give fluorescent derivatives, the fluorous tag in the reagent is eliminated simultaneously. Therefore, excess unreacted reagents in the derivatization reaction solution still have the fluorous tag and could be removed by fluorous solid-phase extraction selectively before high-performance liquid chromatography (HPLC) analysis. By using this reagent, 13 kinds of aliphatic amine (C2–C16) derivatives can be separated within 40 min by reversed-phase HPLC with gradient elution. In this chromatogram, unreacted reagents peak at around 28 min, greatly decrease after fluorous solid-phase extraction, and do not interfere with the quantification of each amine. The detection limits (S/N = 3) for examined aliphatic amines are 3.6–25 fmol per 20 μL injection. We have also applied this reagent successfully to the amino acid analysis.
Keywords: HPLC; Fluorous tag; F-trap; Fluorescence derivatization; Aliphatic amines; Amino acids
Fast-scan cyclic voltammetry for the detection of tyramine and octopamine by Stephanie E. Cooper; B. Jill Venton (329-336).
is an Assistant Professor of Chemistry and Neuroscience at the University of Virginia. She has received an NSF CAREER award and the Eli Lilly Young Analytical Investigator Award. Her research interests include developing new microelectrodes and in vivo detection of neurotransmitters. Tyramine and octopamine are biogenic amine neurotransmitters in invertebrates that have functions analogous to those of the adrenergic system in vertebrates. Trace amounts of these neurotransmitters have also been identified in mammals. The purpose of this study was to develop an electrochemical method using fast-scan cyclic voltammetry at carbon-fiber microelectrodes to detect fast changes in tyramine and octopamine. Because tyramine is known to polymerize and passivate electrode surfaces, waveform parameters were optimized to prevent passivation. No fouling was observed for octopamine when the electrode was scanned from 0.1 to 1.3 V and back at 600 V/s, while a small decrease of less than 10% of the signal was seen for 15 repeated exposures to tyramine. The technique has limits of detection of 18 nM for tyramine and 30 nM for octopamine, much lower than expected levels in insects and lower than basal levels in some brain regions of mammals. Current was linear with concentration up to 5 μM. This voltammetry technique should be useful for measuring tyramine and octopamine changes in insects, such as the fruit fly, Drosophila melanogaster.
Keywords: Phenolamine; Microelectrode; Catecholamine; Fruit fly; Drosophila ; Polytyramine
Critical evaluation of novel dynamic flow-through methods for automatic sequential BCR extraction of trace metals in fly ash by Warunya Boonjob; María Rosende; Manuel Miró; Víctor Cerdà (337-349).
is Associate Professor in analytical chemistry at the University of the Balearic Islands, Spain. His research interest is focused on the development of automatic sample processing strategies for on-line separation and/or preconcentration of trace levels of environmental pollutants exploiting the various generations of flow injection, including the miniaturized Lab-on-a-Valve approach, in hyphenation with modern analytical instrumentation. Two novel dynamic extraction approaches, the so-called sequential injection microcolumn extraction and sequential injection stirred-flow chamber extraction, based on the implementation of a sample-containing container as an external extraction reactor in a sequential injection network, are for the first time, optimized and critically appraised for fractionation assays. The three steps of the original Community Bureau of Reference (BCR) sequential extraction scheme have been performed in both automated dynamic fractionation systems to evaluate the extractability of Cr, Cu, Ni, Pb, and Zn in a standard reference material of coal fly ash (NIST 1633b). In order to find the experimental conditions with the greatest influence on metal leachability in dynamic BCR fractionation, a full-factorial design was applied, in which the solid sample weight (100–500 mg) and the extraction flow rate (3.0–6.0 mL min−1) were selected as experimental factors. Identical cumulative extractabilities were found in both sequential injection (SI)-based methods for most of assayed trace elements regardless of the extraction conditions selected, revealing that both dynamic fractionation systems, as opposed to conventional steady-state BCR extraction, are not operationally defined within the selected range of experimental conditions. Besides, the proposed automated SI assemblies offer a significant saving of operational time with respect to classical BCR test, that is, 3.3 h versus 48 h, for complete fractionation with minimum analyst involvement. Schematic illustration of automatic flow-based setups for dynamic fractionation of trace metals in fly ash
Keywords: Dynamic fractionation; Sequential injection analysis; Stirred-flow chamber extraction; Microcolumn extraction; Coal fly ash; Trace elements
Internal correction of hafnium oxide spectral interferences and mass bias in the determination of platinum in environmental samples using isotope dilution analysis by José Ángel Rodríguez-Castrillón; Mariella Moldovan; J. Ignacio García Alonso (351-362).
has been a researcher and lecturer at the University of Oviedo (Spain) since March 2005. Her current research interests are the development of analytical methods based on the use of stable enriched isotopes and elemental mass spectrometry. A method has been developed for the accurate determination of platinum by isotope dilution analysis, using enriched 194Pt, in environmental samples containing comparatively high levels of hafnium without any chemical separation. The method is based on the computation of the contribution of hafnium oxide as an independent factor in the observed isotope pattern of platinum in the spiked sample. Under these conditions, the ratio of molar fractions between natural abundance and isotopically enriched platinum was independent of the amount of hafnium present in the sample. Additionally, mass bias was corrected by an internal procedure in which the regression variance was minimised. This was possible as the mass bias factor for hafnium oxide was very close to that of platinum. The final procedure required the measurement of three platinum isotope ratios (192/194, 195/194 and 196/194) to calculate the concentration of platinum in the sample. The methodology has been validated using the reference material “BCR-723 road dust” and has been applied to different environmental matrices (road dust, air particles, bulk wet deposition and epiphytic lichens) collected in the Aspe Valley (Pyrenees Mountains). A full uncertainty budget, using Kragten’s spreadsheet method, showed that the total uncertainty was limited only by the uncertainty in the measured isotope ratios and not by the uncertainties of the isotopic composition of platinum and hafnium. Figure Simultaneous correction of hafnium oxide spectral interferences and mass bias in the determination of platinum in environmental samples using isotope dilution analysis
Keywords: Isotope pattern deconvolution; Platinum; Spectral interference correction; Internal mass bias correction; ICP-MS; Isotope dilution analysis; BCR-723 road dust; Environmental samples
The effects of microbial degradation on ignitable liquids by Dee A. Turner; John V. Goodpaster (363-371).
is an Assistant Professor in the Forensic and Investigative Sciences (FIS) Program at Indiana University Purdue University Indianapolis (IUPUI). Research in J. Goodpaster’s laboratory is focused on the identification of explosives and their postblast residues, multivariate statistical approaches to analyzing fiber evidence, microbial degradation of ignitable liquids in fire debris, and evaluation of explosive-detecting canines. The identification of ignitable liquid residues in fire debris is a key finding for determining the cause and origin of a suspicious fire. However, the complex mixtures of organic compounds that comprise ignitable liquids are susceptible to microbiological attack following collection of the sample. Biodegradation can result in selective removal of many of the compounds required for identification of an ignitable liquid. Such degradation has been found to occur rapidly in substrates such as soil, rotting wood, or other organic matter. Furthermore, fire debris evidence must often be stored for extended periods at room temperature prior to analysis due to case backlogs and available evidence storage. Hence, extensive damage to ignitable liquid residues by microbes poses a significant threat to subsequent laboratory work. In this work, the effects of microbial degradation of ignitable liquids in soil have been evaluated as a function of time. Key findings include the loss of n-alkanes, particularly C9–C16, which showed the most dramatic decrease in gasoline as well as the petroleum distillates, while branched alkanes remained unchanged. Monosubstituted benzenes also showed the most dramatic loss in gasoline. In the heavy petroleum distillates, n-alkanes with even carbon numbers were degraded more than n-alkanes with odd carbon numbers. Figure A “fully involved” house fire in Indianapolis, IN
Keywords: Fire debris; Ignitable liquids; Soil; Microbial degradation; Forensic science
Spectroscopic evaluation of a compact magnetically boosted radiofrequency glow discharge for time-of-flight mass spectrometry by P. Vega; J. Pisonero; N. Bordel; A. Tempez; M. Ganciu; A. Sanz-Medel (373-382).
has been Assistant Professor at the Department of Physics at the University of Oviedo since 2006. He was recently awarded a prestigious “Ramon y Cajal” Research Contract. His main scientific interests are related to plasma mass spectrometric techniques for the direct analysis of materials. A compact magnetically boosted radiofrequency glow discharge (GD) has been designed, constructed and its analytical potential evaluated by its coupling to a mass spectrometer (MS). Simple modifications to the original source configuration permitted the insertion of permanent magnets. Small cylindrical Nd–Fe–B magnets (∅ = 4 mm, h = 10 mm) were placed in an in-house-modified GD holder disc that allows easy and fast exchange of the magnets. The different processes taking place within the GD plasma under the influence of a magnetic field, such as sputtering, ionisation processes and ion transport into the MS, were studied using different GD operating conditions. Changes to the ionisation and ion transport efficiency caused by the magnetic field were studied using an rf-GD-TOFMS setup. A magnetic field of 60–75 gauss (G) was found not to affect the sputtering rates but to enhance the analyte ion signal intensities while decreasing the Ar species ion signals. Moreover, magnetic fields in this range were shown not to modify the crater shapes, enabling the fast and sensitive high depth resolved analysis of relatively thick coated samples (micrometre) by using the designed compact magnetically boosted rf-GD-TOFMS.
Keywords: Magnetic field; Radiofrequency glow discharge time-of-flight mass spectrometry; Depth profiling