Nanoscience,nanotechnology and spectrometry

Nanoscience has outgrown its infancy, and nanotechnology has found important applications in our daily life — with many more to come. Although the central concepts of the nano world, namely the changes of particular physical properties on the length scale of individual atoms and molecules, have been known and developed for quite some time already, experimental advances since the 1980s and recognition of the potential of nanomaterials led to a genuine breakthrough of the inherently multidisciplinary nanoscience field. Analytical nanoscience and nanotechnology and especially the use of micro and nano electro mechanical systems, of the quantum dots and of mass spectrometry, currently provide one of the most promising avenues for developments in analytical science, derived from their two main fields of action, namely (a) the analysis of nano-structured materials and (b) their use as new tools for analysis. An overview is given of recent developments and trends in the field, highlighting the importance and point out future directions, while also touching drawbacks, such as emerging concerns about health and environmental issues.     

Determination of the elemental composition of tissues of the cardiovascular system by atomic spectrometry, mass spectrometry and X-ray spectrometry methods

The review discusses the published data on the concentrations of chemical elements in tissues of the cardiovascular system determined by atomic absorption and atomic emission spectrometry, mass spectrometry, and also X-ray fluorescence analysis, proton-induced X-ray emission, and X-ray microanalysis. The main parameters of X-ray spectrometry methods used for the examination of the cardiovascular system are compared, the new trends in the analysis of these samples and the main sample preparation approaches are considered.     

Atmospheric pressure chemical ionization of fluorinated phenols in atmospheric pressure chemical ionization mass spectrometry, tandem mass spectrometry, and ion mobility spectrometry

Atmospheric pressure chemical ionization (APCI)-mass spectrometry (MS) for fluorinated phenols (C6H5-xFxOH Where x = 0-5) in nitrogen with Cl- as the reagent ion yielded product ions of M Cl- through ion associations or (M-H)- through proton abstractions. Proton abstraction was controllable by potentials on the orifice and first lens, suggesting that some proton abstraction occurs through collision induced dissociation (CID) in the interface region. This was proven using CID of adduct ions (M Cl-) with Q2 studies where adduct ions were dissociated to Cl- or proton abstracted to (M-H)-. The extent of proton abstraction depended upon ion energy and structure in order of calculated acidities: pentafluorophenol > tetrafluorophenol > trifluorophenol > difluorophenol. Little or no proton abstraction occurred for fluorophenol, phenol, or benzyl alcohol analogs. Ion mobility spectrometry was used to determine if proton abstraction reactions passed through an adduct intermediate with thermalized ions and mobility spectra for all chemicals were obtained from 25 to 200 degrees C. Proton abstraction from M Cl- was not observed at any temperature for phenol, monofluorophenol, or difluorophenol. Mobility spectra for trifluorophenol revealed the kinetic transformations to (M-H)- either from M Cl- or from M2 Cl- directly. Proton abstraction was the predominant reaction for tetra- and penta-fluorophenols. Consequently, the evidence suggests that proton abstraction occurs from an adduct ion where the reaction barrier is reduced with increasing acidity of the O-H bond in C6H5-xFxOH.     

Identification of two-dimensionally separated human cerebrospinal fluid proteins by N-terminal sequencing, matrix-assisted laser desorption/ionization--mass spectrometry, nanoliquid chromatography-electrospray ionization-time of flight-mass spectrometry, and tandem mass spectrometry

Optimal application of biological mass spectrometry (MS) in combination with two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) of human cerebrospinal fluid (CSF) can lead to the identification of new potential biological markers of neurological disorders. To this end, we analyzed a number of 2-D PAGE protein spots in a human CSF pool using spot co-localization, N-terminal sequencing, matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) and nanoliquid chromatography-electrospray ionization-time of flight-mass spectrometry (nanoLC-ESI-TOF-MS) with tandem MS switching. Our constructed CSF master contained 469 spots after image analysis and processing of 2-D gels. Upon visual inspection of our CSF master with the CSF pattern available on the ExPASy server, it was possible to locate and annotate 15 proteins. N-terminal sequence analysis and MALDI-MS peptide mass fingerprint analysis of both silver- and Coomassie Brilliant Blue (CBB) G-250-stained protein spots after in situ trypsin digest not only confirmed nine of the visually annotated spots but additionally resolved the identity of another 13 spots. Six of these proteins were not annotated on the 2-D ExPASy map: complement C3 alpha-chain (1321-1663), complement factor B, cystatin C, calgranulin A, hemoglobin beta-chain, and beta-2-microglobulin. It was clear that MALDI-MS identification from CBB G-250-stained, rather than from silver-stained, spots was more successful. In cases where no N-terminal sequence and/or no clear MALDI-MS result was available, nanoLC-ESI-TOF-MS and tandem MS automated switching was used to clarify and/or identify these protein spots by generating amino acid sequence tags. In addition, enrichment of the concentration of low-abundant proteins on 2-D PAGE was obtained by removal of albumin and immunoglobulins from the CSF pool using affinity chromatography. Subsequent analysis by 2-D PAGE of the fractionated CSF pool showed various new silver-stainable protein spots, of which four were identified by nanoLC-ESI-TOF-MS and tandem MS switching. No significant homology was found in either protein or DNA databases, indicating than these spots were unknown proteins.     

Comparative determinations of lead in soils by X-ray fluorescence, atomic absorption spectrometry, and atomic emission spectrometry

Summary Determinations of lead in different soil samples were carried out by X-ray fluorescence (XRF) (borate-glass fusion 13), atomic absorption spectrometry (AAS), and induced coupled plasma atomic emission spectrometry (ICP-AES) (aqua regia digestion). The concentration ranges in contaminated soils were 10 to 200 wt. ppm and 0.05 to 3.0 wt.%. The detection limit of XRF (5 ppm) is adequate; the precision of AAS (1%) is the best; but the relative accuracy of all three methods does not surpass 10%. This is because of errors in sampling and sample preparation, the latter being difficult to judge. Determinations with different methods and correlation analysis of the results are necessary.

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Vergleichende Bestimmung von Blei in Böden durch Röntgenfluorescenz, AAS und AES

Zusammenfassung Bleibestimmungen in verschiedenen Bodenproben wurden mit der RFA (Boratglas-Schmelze 13), AAS (Königswasser-Aufschluß) und ICP-AES (Königswasser-Aufschluß) durchgeführt. Die Konzentrationsbereiche waren 10 bis 200 Gew.-ppm und 0,05 bis 3,0 Gew.-% in kontaminierten Bodenproben. Die Nachweisgrenze der RFA (5 ppm) ist ausreichend; die Reproduzierbarkeit der AAS (1 %) ist die beste, aber die Richtigkeit der drei Methoden ist nicht besser als 10% relativ. Gründe dafür sind Fehler bei der Probenahme und bei der Probenvorbereitung; letztere sind schwer zu erkennen. Bestimmungen mit mehreren Methoden und Korrelationsanalyse der Resultate sind notwendig.

     

Comparative analysis of ancient ceramics by neutron activation analysis,inductively coupled plasma-optical-emission spectrometry,inductively coupled plasma-mass spectrometry,and X-ray fluorescence

The accurate measurement of the maximum possible number of elements in ancient ceramic samples is the main requirement in provenance studies. For this reason neutron activation analysis (NAA) and X-ray fluorescence (XRF) have been successfully used for most of the studies. In this work the analytical performance of inductively coupled plasma-optical-emission spectrometry (ICP-OES) and inductively coupled plasma-mass spectrometry (ICP-MS) has been compared with that of XRF and NAA for the chemical characterization of archaeological pottery. Correlation coefficients between ICP techniques and XRF or NAA data were generally better than 0.90. The reproducibility of data calculated on a sample prepared and analysed independently ten times was approximately 5% for most of the elements. Results from the ICP techniques were finally evaluated for their capacity to identify the same compositional pottery groups as results from XRF and NAA analysis, by use of multivariate statistics.     

Trace characterization of high-purity molybdenum and tungsten by electrothermal atomic absorption spectrometry, inductively coupled plasma atomic emission spectrometry, inductively coupled plasma mass spectrometry and total reflection X-ray fluorescence spectrometry involving analyte—matrix separation

A technique for the separation of 42 trace elements from up to 5 g of molybdenum and tungsten matrices was developed by means of the radiotracer technique. It is based on adsorption of the analyses on the cation exchanger Dowex 50 W x 9 from a 4% H₂O₂/0.01 mol 1⁻¹ HNO₃ solution followed by their elution with 15 ml of 4 mol I⁻¹ HNO₃ in the opposite flow direction. Both matrices were removed with a separation factor > 10⁴. The separation technique was applied to the analysis of these materials by electrothermal atomic absorption spectrometry, inductively coupled plasma atomic emission spectrometry, inductively coupled plasma mass spectrometry and total reflection X-ray fluorescence spetrometry. For all the determination methods used, the limits of detection are given and compared with those of other methods. With inductively coupled plasma mass spectrometry, for 22 of the 30 assayed elements, limits of detection at the sub-ng g⁻¹ level were achieved. The results are compared with those obtained by radiochemical neutron activation analysis in this work and by glow discharge mass spectrometry, secondary ion mass spectrometry, isotope dilution mass spectrometry and by solution spectrometric methods in other laboratories.     

Chromatography,mass spectrometry,and molecular modeling studies on ammodytoxins

The ammodytoxins (Atxs) are neurotoxic phospholipases which occur in Vipera ammodytes ammodytes (Vaa) snake venom. There are three Atx isoforms, A, B, and C, which differ in only five amino acid positions at the C-terminus but differ substantially in their toxicity. The objective of this study was to establish an analytical method for unambiguous identification of all three isoforms and to use the method to assess a procedure for purification of the most toxic phospholipase, AtxA, from the venom. Isolation procedure for AtxA consisted of isolation of Atx-cross-reactive material (proteins recognized by anti-Atx antibodies), by use of an affinity column, then cation exchange on CIM (Convective Interaction Media) disks. The purification procedure was monitored by means of reversed-phase chromatography (RPC) and mass spectrometry (MS). Although previous cation exchange of the pure isoforms enabled separate elution of AtxA from B and C, separation of AtxA from Atxs mixture was not accomplished. RPC was not able to separate the Atx isoforms, whereas an MS based approach proved to be more powerful. Peptides resulting from tryptic digestion of Atxs which enable differentiation between the three isoforms were successfully detected and their sequences were confirmed by post-source decay (PSD) fragmentation. Separation of Atx isoforms by ion-exchange chromatography is most presumably prevented by Atxs heterodimer formation. The tendency of Atxs to form homodimers and heterodimers of similar stability was confirmed by molecular modeling.     

Metabolomics of transgenic maize combining Fourier transform-ion cyclotron resonance-mass spectrometry,capillary electrophoresis-mass spectrometry and pressurized liquid extraction

In this work, the potential of combining capillary electrophoresis-time-of-flight-mass spectrometry (CE-TOF-MS) and Fourier transform-ion cyclotron resonance-mass spectrometry (FT-ICR-MS) for metabolomics of genetically modified organisms (GMOs) is demonstrated. Thus, six different varieties of maize, three of them transgenic (PR33P66 Bt, Tietar Bt and Aristis Bt) and their corresponding isogenic lines (PR33P66, Tietar and Aristis) grown under the same field conditions, were analyzed. Based on the ultrahigh resolution and remarkable mass accuracy provided by the 12-T FT-ICR-MS it was possible to directly analyze a good number of metabolites whose identity could be proposed based on their specific isotopic pattern. For identification of metabolite isomers, CE-TOF-MS was also used combining the information on nominal mass with electrophoretic mobility corroborating in that way the identity of several new biomarkers. Furthermore, PLE extractions were evaluated in order to establish selective extraction as an additional criterion to obtain useful information in maize metabolomics. Differences in the metabolite levels were found between the three transgenic maize varieties compared with their wild isogenic lines in some specific metabolic pathways. To our knowledge, this is the first time that an approach as the one presented in this work (pressurized liquid extraction + FT-ICR-MS + CE-TOF-MS) is shown for a metabolomic study.     

Analysis of flavonoids: tandem mass spectrometry, computational methods, and NMR

Due to the increasing understanding of the health benefits and chemopreventive properties of flavonoids, there continues to be significant effort dedicated to improved analytical methods for characterizing the structures of flavonoids and monitoring their levels in fruits and vegetables, as well as developing new approaches for mapping the interactions of flavonoids with biological molecules. Tandem mass spectrometry (MS/MS), particularly in conjunction with liquid chromatography (LC), is the dominant technique that has been pursued for elucidation of flavonoids. Metal complexation strategies have proven to be especially promising for enhancing the ionization of flavonoids and yielding key diagnostic product ions for differentiation of isomers. Of particular value is the addition of a chromophoric ligand to allow the application of infrared (IR) multiphoton dissociation as an alternative to collision-induced dissociation (CID) for the differentiation of isomers. CID, including energy-resolved methods, and nuclear magnetic resonance (NMR) have also been utilized widely for structural characterization of numerous classes of flavonoids and development of structure/activity relationships.The gas-phase ion chemistry of flavonoids is an active area of research particularly when combined with accurate mass measurement for distinguishing between isobaric ions. Applications of a variety of ab initio and chemical computation methods to the study of flavonoids have been reported, and the results of computations of ion and molecular structures have been shown together with computations of atomic charges and ion fragmentation. Unambiguous ion structures are obtained rarely using MS alone. Thus, it is necessary to combine MS with spectroscopic techniques such as ultraviolet (UV) and NMR to achieve this objective. The application of NMR data to the mass spectrometric examination of flavonoids is discussed.     

The microdetermination of chloride,sulphate, phosphate and nitrite by reflectance spectrometry

Quantitative spot tests with a reflectance spectrometer have been developed for chloride (10–320 p.p.m.), sulphate (10–120 p.p.m.), phosphate (2–30 and 10–180 p.p.m.) and nitrite (1–35 and 10–100 p.p.m.). There are few interferences with these tests, and their effects can be overcome by standard techniques except for the interference from phosphate when it is present in the sulphate test, in large concentrations.     

Analytical information from mass spectrometry,past and future

Two basic reasons are proposed for the tremendous success and future promise of mass spectrometry: (1) the unusually high volume of data obtainable from unusually small samples and (2) the success in converting these data into structural and quantitative information. The ion abundance dimension of mass spectrometric data is remarkable in its pico-to-ttogram sensitivity and >10⁶ dynamic range, and the mass scale dimension is uniquely high in the number of resolution increments for larger molecule ionization and high resolution. Additional dimensions of data arise from chromatographic coupling to mass spectrometry and tandem mass spectrometry, as well as from alternative ionization and ion reaction methods. Converting these data into chemical information is equally important. Past progress in these areas has been cyclical; for the immediate future a greater research emphasis is urged to convert data to information through better understanding of the relevant chemistry and better utilization of modern computer methods.     

Field desorption mass spectrometry,fast atom bombardment mass spectrometry and fast atom bombardment tandem mass spectrometry of echinacoside,the main caffeoyl-glycoside from Echinacea angustifolia roots (Asteraceae)

The mass spectral fragmentation of echinacoside, a pharmacologically active caffeoyl-glycoside isolated from Echinacea angustifolia roots, has been investigated using different soft-ionization techniques, field desorption and fast atom bombardment (positive and negative ions) mass Spectrometry. Both ionization modes are successful in molecular mass determination and furnish approximately equivalent structural information. A fast atom bombardment tandem mass spectrometry approach (negative ions) was developed for the study of the fragmentation pathways and for the detection of echinacoside in crude plant extracts. The results demonstrate the usefulness of this technique for the rapid search of this important caffeoyl-glucoside directly in natural complex matrices.     

Predicting percent composition of blends of biodiesel and conventional diesel using gas chromatography-mass spectrometry, comprehensive two-dimensional gas chromatography-mass spectrometry, and partial least squares analysis

The percent composition of blends of biodiesel and conventional diesel from a variety of retail sources were modeled and predicted using partial least squares (PLS) analysis applied to gas chromatography-total-ion-current mass spectrometry (GC-TIC), gas chromatography-mass spectrometry (GC-MS), comprehensive two-dimensional gas chromatography-total-ion-current mass spectrometry (GCxGC-TIC) and comprehensive two-dimensional gas chromatography-mass spectrometry (GCxGC-MS) separations of the blends. In all four cases, the PLS predictions for a test set of chromatograms were plotted versus the actual blend percent composition. The GC-TIC plot produced a best-fit line with slope = 0.773 and y-intercept = 2.89, and the average percent error of prediction was 12.0%. The GC-MS plot produced a best-fit line with slope = 0.864 and y-intercept = 1.72, and the average percent error of prediction was improved to 6.89%. The GCxGC-TIC plot produced a best-fit line with slope = 0.983 and y-intercept = 0.680, and the average percent error was slightly improved to 6.16%. The GCxGC-MS plot produced a best-fit line with slope = 0.980 and y-intercept = 0.620, and the average percent error was 6.12%. The GCxGC models performed best presumably due to the multidimensional advantage of higher dimensional instrumentation providing more chemical selectivity. All the PLS models used 3 latent variables. The chemical components that differentiate the blend percent compositions are reported.     

Potential of capillary electrophoresis, tandem mass spectrometry and coupled capillary electrophoresis-tandem mass spectrometry as diagnostic tools

Urine and blood samples from patients with known metabolic disorders have been analyzed by CE, MS-MS and CE-MS-MS. For the identification of defects in acylcarnitine metabolism, blood spots on filter paper were analyzed using an MS-MS "neonatal screening" approach. Direct CE-MS-MS analysis was used for the analysis of urine samples from patients with different metabolic disorders, including galactosemia, neuroblastoma, Zellweger syndrome, propionic acidemia and alcaptonuria. The sensitivity of the CE-MS-MS method was increased by use of multiple reaction monitoring.     

Cadmium,copper, lead,and zinc determination in precipitation: A comparison of inductively coupled plasma atomic emission spectrometry and graphite furnace atomization atomic absorption spectrometry

Selected trace element analysis for cadmium, copper, lead, and zinc in precipitation samples by inductively coupled plasma atomic emission Spectrometry (ICP) and by atomic absorption spectrometry with graphite furnace atomization (AAGF) have been evaluated. This task was conducted in conjunction with a longterm study of precipitation chemistry at high altitude sites located in remote areas of the southwestern United States. Coefficients of variation and recovery values were determined for a standard reference water sample for all metals examined for both techniques. At concentration levels less than 10 micrograms per liter AAGF analyses exhibited better precision and accuracy than ICP. Both methods appear to offer the potential for cost-effective analysis of trace metal ions in precipitation.     

A novel isotope analysis of oxygen in uranium oxides: comparison of secondary ion mass spectrometry,glow discharge mass spectrometry and thermal ionization mass spectrometry

The natural variation of the oxygen isotopic composition is used among geologists to determine paleotemperatures and the origin of minerals. In recent studies, oxygen isotopic composition has been recognized as a possible tool for identification of the origin of seized uranium oxides in nuclear forensic science. In the last 10 years, great effort has been made to develop new direct and accurate n(¹⁸O)/n(¹⁶O) measurements methods. Traditionally, n(¹⁸O)/n(¹⁶O) analyses are performed by gas mass spectrometry. In this work, a novel oxygen isotope analysis by thermal ionization mass spectrometry (TIMS), using metal oxide ion species (UO⁺), is compared to the direct methods: glow discharge mass spectrometry (GDMS) and secondary ion mass spectrometry (SIMS). Because of the possible application of the n(¹⁸O)/n(¹⁶O) ratio in nuclear forensics science, the samples were solid, pure UO₂ or U₃O₈ particles. The precision achieved using TIMS analysis was 0.04%, which is similar or even better than the one obtained using the SIMS technique (0.05%), and clearly better if compared to that of GDMS (0.5%). The samples used by TIMS are micrograms in size. The suitability of TIMS as a n(¹⁸O)/n(¹⁶O) measurement method is verified by SIMS measurements. In addition, TIMS results have been confirmed by characterizing the n(¹⁸O)/n(¹⁶O) ratio of UO₂ sample also by the traditional method of static vacuum mass spectrometry at the University of Chicago.