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1.
Jennifer L. Gottfried Russell S. Harmon Frank C. De Lucia Jr. Andrzej W. Miziolek 《Spectrochimica Acta Part B: Atomic Spectroscopy》2009,64(10):1009
A large suite of natural carbonate, fluorite and silicate geological materials was studied using laser-induced breakdown spectroscopy (LIBS). Both single- and double-pulse LIBS spectra were acquired using close-contact benchtop and standoff (25 m) LIBS systems. Principal components analysis (PCA) and partial least squares discriminant analysis (PLS-DA) were used to identify the distinguishing characteristics of the geological samples and to classify the materials. Excellent discrimination was achieved with all sample types using PLS-DA and several techniques for improving sample classification were identified. The laboratory double-pulse LIBS system did not provide any advantage for sample classification over the single-pulse LIBS system, except in the case of the soil samples. The standoff LIBS system provided comparable results to the laboratory systems. This work also demonstrates how PCA can be used to identify spectral differences between similar sample types based on minor impurities. 相似文献
2.
A method for the quantitative elemental analysis of surface soil samples using laser-induced breakdown spectroscopy (LIBS)
was developed and applied to the analysis of bulk soil samples for discrimination between specimens. The use of a 266 nm laser
for LIBS analysis is reported for the first time in forensic soil analysis. Optimization of the LIBS method is discussed,
and the results compared favorably to a laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) method previously
developed. Precision for both methods was <10% for most elements. LIBS limits of detection were <33 ppm and bias <40% for
most elements. In a proof of principle study, the LIBS method successfully discriminated samples from two different sites
in Dade County, FL. Analysis of variance, Tukey’s post hoc test and Student’s t test resulted in 100% discrimination with no type I or type II errors. Principal components analysis (PCA) resulted in clear
groupings of the two sites. A correct classification rate of 99.4% was obtained with linear discriminant analysis using leave-one-out
validation. Similar results were obtained when the same samples were analyzed by LA-ICP-MS, showing that LIBS can provide
similar information to LA-ICP-MS. In a forensic sampling/spatial heterogeneity study, the variation between sites, between
sub-plots, between samples and within samples was examined on three similar Dade sites. The closer the sampling locations,
the closer the grouping on a PCA plot and the higher the misclassification rate. These results underscore the importance of
careful sampling for geographic site characterization. 相似文献
3.
4.
In the U.S., all clinical laboratory testing is regulated by the Clinical Laboratory Improvement Amendments (CLIA) (). The CLIA link test quality and adherence to a body of testing regulations intended to ensure accurate, reliable, and timely patient test results. The goal of the CLIA legislation was to ensure a minimum, fundamental level of quality. In the context of “NEXUS,” quality must “go beyond getting the ‘right’ answer on the ‘right’ patient that can be interpreted against ‘right’ reference values. CLIA regulations with specific minimum, performance requirements, or safeguards, are designed to prevent testing errors. The US Institute of Medicine found that testing processes fail as a result of human error, lack of documentation, and lack of test management. In the latest (2004) interpretations of CLIA regulations, the minimum quality control requirement continues to be analyzing at least two external, liquid quality control materials per test per day. In 1995, we proposed that the responsibility for achieving quality test results shifts from the sole purview of the laboratory director to an “alliance” of laboratory professionals, manufacturers, and regulators. The EQC (equivalent quality control) concept as proposed is a positive step in achieving this alliance. With the obvious lack of scientific and statistical robustness, EQC falls far short of ensuring quality. Achieving the “NEXUS Vision” for quality laboratory testing will not come solely from laboratory professionals. The NEXUS is about how to ensure the full-quality assessment of the testing process – pre-analytical, analytical, and post-analytical.Presented at the 10th Conference Quality in the Spotlight, March 2005, Antwerp, Belgium. 相似文献
5.
Zs. Kasztovszky Z. Kis T. Belgya W. Kockelmann S. Imberti G. Festa A. Filabozzi C. Andreani A. Kirfel K. T. Biró K. Dúzs Zs. Hajnal P. Kudejova M. Tardocchi 《Journal of Radioanalytical and Nuclear Chemistry》2008,278(3):661-664
The aim of the ‘Ancient Charm’ project is combining neutron tomography, prompt gamma activation analysis, time of flight neutron
diffraction and neutron resonance transmission to generate elemental, and phase compositions of complex museum objects in
3D. To develop a protocol for such investigations, complex test samples were constructed and then analyzed by each method.
The ‘black boxes’ are sealed iron and aluminum walled cubes, containing 2D or 3D arrangements of materials relevant for the
compositions of archaeological samples. The experimental results obtained from bulk PGAA at BNC and TOF-ND at ISIS on two
selected boxes are reported. 相似文献
6.
René Dybkaer 《Accreditation and quality assurance》2011,16(12):649-651
In the slow evolution of the International vocabulary of metrology (VIM), the first concept of ‘quantity’ has now been divided
generically into ‘ordinal quantity’ and a coordinate primitive without definition and term. An analysis of the concepts by
their characteristics is made, and the nature of inheritance is discussed in response to a recent communication in this journal.
A completion of the initiated generic division of ‘quantity’ is suggested, and a neoterm for the sister of ‘ordinal quantity’
is offered on the basis of two proposals. 相似文献
7.
M.D Eddy 《Foundations of Chemistry》2004,6(2):161-175
In the 18th century, the concept of ‘affinity’, ‘principle’ and ‘element’ dominated chemical discourse, both inside and outside
the laboratory. Although much work has been done on these terms and the methodological commitments which guided their usage,
most studies over the past two centuries have concentrated on their application as relevant to Lavoisier's oxygen theory and
the new nomenclature. Kim's affinity challenges this historiographical trajectory by looking at several French chemists in the light of their private thoughts,
public disputations and communal networks. In doing so, she tells a complex story which points to the methodological and practical
importance of industrial and medical chemistry. The following review highlights the advantages and snares of such an approach
and makes a few historiographical points along the way.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
8.
S Chandrasekhar 《Research on Chemical Intermediates》1997,23(1):55-62
By the temporal Uncertainty principle, chemical systems may be described in terms of ‘kinetic’ or ‘thermodynamic’ complementary
formulations, based on rate or equilibrium constants, and free energy changes respectively. Thereby, the paradox of the dichotomous
formulations of the Curtin-Hammett principle is resolved. A new formulation of the principle is suggested, and a fundamental
conflict with transition state theory is indicated. 相似文献
9.
Frank C. De Lucia Jr. Jennifer L. Gottfried Chase A. Munson Andrzej W. Miziolek 《Spectrochimica Acta Part B: Atomic Spectroscopy》2007,62(12):1399-1404
Detecting trace explosive residues at standoff distances in real-time is a difficult problem. One method ideally suited for real-time standoff detection is laser-induced breakdown spectroscopy (LIBS). However, atmospheric oxygen and nitrogen contributes to the LIBS signal from the oxygen- and nitrogen-containing explosive compounds, complicating the discrimination of explosives from other organic materials. While bathing the sample in an inert gas will remove atmospheric oxygen and nitrogen interference, it cannot practically be applied for standoff LIBS. Alternatively, we have investigated the potential of double pulse LIBS to improve the discrimination of explosives by diminishing the contribution of atmospheric oxygen and nitrogen to the LIBS signal. These initial studies compare the close-contact (< 1 m) LIBS spectra of explosives using single pulse LIBS in argon with double pulse LIBS in atmosphere. We have demonstrated improved discrimination of an explosive and an organic interferent using double pulse LIBS to reduce the air entrained in the analytical plasma. 相似文献
10.
René Dybkaer 《Accreditation and quality assurance》2007,12(10):553-557
Laboratory medicine provides results for quantities as well as for properties having no magnitude. The terminology of the
latter is less well established and sources are contradictory. Two recent papers on “protometrology” published in this journal
offer an opportunity to discuss the necessary concept systems. The delineations of “metrology” versus “protometrology”, “observation”
versus “measurement”, and the generic division of “property” are examined with emphasis on avoiding conflict with the International
Vocabulary of Metrology. It is suggested that having “examination” as a top generic concept coupled with systematic modifiers
for division, especially ‘nominal’ and ‘ordinal’, is a preferable terminological solution.
相似文献
René Dybkaer |
11.
Interferences (overlaps) occurring when lines of other elements affect either peak or background measurements can cause errors
in quantitative WD analysis, but may be minimised by suitable choices of analysis conditions such as spectrometer crystal,
background offsets, and pulse-height analyser settings. Computer spectrum-simulation is much more effective than reference
to wavelength tables for investigating interferences. The ‘Virtual WDS’ simulation program developed by the present authors,
hitherto applied only to ‘ordinary’ elements (Z ≥ 11), has been extended to light elements for which evaporated multilayers are used in place of true crystals. ‘Virtual
WDS’ utilises experimentally recorded light-element K spectra and L and M spectra of heavier elements in the same wavelength
range. It is impractical to record all high-order peaks, so computed line profiles are used, with widths and intensities interpolated
from a limited set of observations. The relative positions of first and higher order peaks are affected significantly by the
refractive index of the multilayer, requiring modification of the Bragg equation. Suppression of high orders by pulse-height
analysis is less effective than for ‘normal’ wavelengths, owing to the breadth of the pulse-height distribution for low X-ray
energies. Simulation using a Gaussian expression aids optimisation of threshold and window-width settings. 相似文献
12.
Sustainable development is the new design of an old concept, now emerging from the acute endangering of our habitat. Coined
by the Brundlandt Commission in 1987, sustainable development was defined as ‘Development that meets the needs of the present
without compromising the ability of future generations to meet their own needs’ (World commission on Environment and Development,
Our Common Future, Oxford University Press, Oxford, 1987). It appeared on the world stage during the UNO Earth Summit in Rio,
1992. Sustainability became the key term of the ‘Agenda 21’ (United Nations Conference for Education and Development, Earth
Summit, Agenda 21, The United Nations Programme of action for Sustainable Development, United Nations, New York, 1992). The
‘Agenda 21’ is adopted by 178 states, although to date not all signatories have ratified the Agenda. Sustainable solutions
should aim to harmonize ecological equilibrium, economic stability, and social harmony. But in the course of the years, the
interpretation of the concept became more and more complicated and its context is becoming fuzzy.
Extended version of a presentation given during a Baltic University Programme's international workshop on ‘Sustainable Chemistry
and Biochemistry’ at St. Marienthal, Germany, February 15–17, 2005 相似文献
13.
Benjamin E. Naes Sayuri Umpierrez Scott Ryland Cleon Barnett Jose R. Almirall 《Spectrochimica Acta Part B: Atomic Spectroscopy》2008
Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), micro X-ray fluorescence spectroscopy (μXRF), and laser induced breakdown spectroscopy (LIBS) are compared in terms of discrimination power for a glass sample set consisting of 41 fragments. Excellent discrimination results (> 99% discrimination) were obtained for each of the methods. In addition, all three analytical methods produced very similar discrimination results in terms of the number of pairs found to be indistinguishable. The small number of indistinguishable pairs that were identified all originated from the same vehicle. The results also show a strong correlation between the data generated from the use of µXRF and LA-ICP-MS, when comparing µXRF strontium intensities to LA-ICP-MS strontium concentrations. A 266 nm laser was utilized for all LIBS analyses, which provided excellent precision (< 10% RSD for all elements and < 10% RSD for all ratios, N = 5). The paper also presents a thorough data analysis review for forensic glass examinations by LIBS and suggests several element ratios that provide accurate discrimination results related to the LIBS system used for this study. Different combinations of 10 ratios were used for discrimination, all of which assisted with eliminating Type I errors (false exclusions) and reducing Type II errors (false inclusions). The results demonstrate that the LIBS experimental setup described, when combined with a comprehensive data analysis protocol, provides comparable discrimination when compared to LA-ICP-MS and μXRF for the application of forensic glass examinations. Given the many advantages that LIBS offers, most notably reduced complexity and reduced cost of the instrumentation, LIBS is a viable alternative to LA-ICP-MS and μXRF for use in the forensic laboratory. 相似文献
14.
After the International Laboratory Accreditation Cooperation (ILAC) had taken in 2004, the resolution to conduct accreditation
of producers of reference materials according to ISO Guide 34 ‘General requirements for the competence of reference material
producers’ in combination with ISO/IEC 17025 ‘General requirements for the competence of testing and calibration laboratories’,
ISO/REMCO, the ISO Committee on Reference Materials, decided in 2005 to revise ISO Guide 34 to align it closer with ISO/IEC
17025 and to clarify certain issues for accreditors and producers seeking accreditation without adding new requirements. Moreover,
the publication in 2007 of ISO/IEC Guide 99 ‘International vocabulary of metrology—Basic and general concepts and associated
terms (VIM)’ triggered additional adaptations of the guide. 相似文献
15.
René Dybkaer 《Accreditation and quality assurance》2011,16(2):105-108
The present diversity in the definitions and relations of ‘verification’ and ‘validation’ is impractical for such transdisciplinary
concepts. General dictionaries, international special language vocabularies and minor lists show that the respective recent
formulations by the International Organization for Standardization (ISO) and the Joint Committee for Guides in Metrology (JCGM)
are the most quoted. The characteristics of these concepts are elucidated terminologically, and separate concept systems are
made for ISO and JCGM to arrive at a preference for a generic rather than an associative relation. 相似文献
16.
I. Rauschenbach E.K. Jessberger S.G. Pavlov H.-W. Hübers 《Spectrochimica Acta Part B: Atomic Spectroscopy》2010
We report on our ongoing studies to develop Laser-Induced Breakdown Spectroscopy (LIBS) for planetary surface missions to Mars and other planets and moons, like Jupiter's moon Europa or the Earth's moon. Since instruments for space missions are severely mass restricted, we are developing a light-weight miniaturized close-up LIBS instrument to be installed on a lander or rover for the in-situ geochemical analysis of planetary surface rocks and coarse fines. The total mass of the instrument will be ≈ 1 kg in flight configuration. Here we report on a systematic performance study of a LIBS instrument equipped with a prototype laser of 216 g total mass and an energy of 1.8 mJ. The LIBS measurements with the prototype laser and the comparative measurements with a regular 40 mJ laboratory laser were both performed under Martian atmospheric conditions. 相似文献
17.
Firstly, the contribution summarises important results of the work dedicated to the formation of ultrahydrophobic aluminium surfaces. This treatment comprises sulphuric acid anodisation under intensified temperature and current density conditions (‘SAAi’) as well as subsequent chemical modification (‘C’). The usual sulphuric acid anodisation (‘SAAu’) was included for comparison. These various states were examined by electrochemical impedance spectrometry (EIS) to derive typical EIS-related features, especially for the ultrahydrophobic states compared to the anodised surfaces. Based on well-defined spectra types, modelling yielded results, preferentially with regard to the nano-porosity of the oxidic layers. EIS measurements allowed the conclusion that the original nano-porosity underwent specific changes due to the chemical modification variants employed. The chances of EIS predicting the stability of the ultrahydrophobically modified systems are critically assessed on the background of standardised weathering tests. 相似文献
18.
René Dybkaer 《Accreditation and quality assurance》2011,16(10):479-482
19.
The well-known divergence between the present ‘state of the art’ of thermogravimetry and industrial requirements is discussed.
Sources of errors are analyzed and the optimization of measuring conditions is discussed regarding the problems associated
with static and dynamic (flow) atmospheres, and interactions between materials and gases or vapors. Recommendations for gas-flow
control systems and vapor sources are given. Thermal stability and the kinetics of gas-evolving, reversible, thermal decompositions
of solids are discussed. The scope of TG-derived kinetics for practical use is examined. Some new characteristic points of
TG curves are proposed and defined, e.g. ‘procedure-independent decomposition temperature’ and ‘augmented decomposition temperature’
(obtained at pseudo-equilibrium conditions).
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
20.
Harmon RS Shughrue KM Remus JJ Wise MA East LJ Hark RR 《Analytical and bioanalytical chemistry》2011,400(10):3377-3382
Conflict minerals is a term applied to ores mined in conditions of armed conflict and human rights abuse. Niobium and tantalum
are two rare metals whose primary natural occurrence is in the complex oxide minerals columbite and tantalite, the ore of
which is commonly referred to as coltan. The illicit export of coltan ore from the Democratic Republic of the Congo is thought
to be responsible for financing the ongoing civil conflicts in this region. Determining the chemical composition of an ore
is one of the means of ascertaining its provenance. Laser-induced breakdown spectroscopy (LIBS) offers a means of rapidly
distinguishing different geographic sources for a mineral because the LIBS plasma emission spectrum provides the complete
chemical composition (i.e., “chemical fingerprint”) of any material in real time. To test this idea for columbite–tantalite,
three sample sets were analyzed. Partial least squares discriminant analysis (PLSDA) allows correct sample-level geographic
discrimination at a success rate exceeding 90%. 相似文献