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Fundamental Principles of X-Ray Fluorescence (XRF)The XRF method depends on fundamental principles that are common to several other
instrumental methods involving interactions between electron beams and x-rays with
samples, including: X-ray spectroscopy (e.g., SEM - EDS), X-ray diffraction (XRD), and
wavelength dispersive spectroscopy (microprobe WDS).
The analysis of major and trace elements in geological materials by x-ray fluorescence
is made possible by the behavior of atoms when they interact with radiation. When
materials are excited with high-energy, short wavelength radiation (e.g., X-rays), they
can become ionized. If the energy of the radiation is sufficient to dislodge a tightly-held
inner electron, the atom becomes unstable and an outer electron replaces the missing
inner electron. When this happens, energy is released due to the decreased binding
energy of the inner electron orbital compared with an outer one. The emitted radiation
is of lower energy than the primary incident X-rays and is termed fluorescent radiation.
Because the energy of the emitted photon is characteristic of a transition between
specific electron orbitals in a particular element, the resulting fluorescent X-rays can be
used to detect the abundances of elements that are present in the sample.
X-Ray Fluorescence (XRF) Instrumentation - How Does It Work?The analysis of major and trace elements in geological materials by XRF is made
possible by the behavior of atoms when they interact with X-radiation. An XRF
spectrometer works because if a sample is illuminated by an intense X-ray beam, known
as the incident beam, some of the energy is scattered, but some is also absorbed within
the sample in a manner that depends on its chemistry. The incident X-ray beam is
typically produced from a Rh target, although W, Mo, Cr and others can also be used,
depending on the application.
Show Caption
When this primary X-ray beam illuminates the sample, it is said to be excited. The
excited sample in turn emits X-rays along a spectrum of wavelengths characteristic of
the types of atoms present in the sample. How does this happen? The atoms in the
sample absorb X-ray energy by ionizing, ejecting electrons from the lower (usually K
and L) energy levels. The ejected electrons are replaced by electrons from an outer,
higher energy orbital. When this happens, energy is released due to the decreased
binding energy of the inner electron orbital compared with an outer one. This energy
release is in the form of emission of characteristic X-rays indicating the type of atom
present. If a sample has many elements present, as is typical for most minerals and
rocks, the use of a Wavelength Dispersive Spectrometer much like that in
an EPMA allows the separation of a complex emitted X-ray spectrum into characteristic
wavelengths for each element present. Various types of detectors (gas flow proportional
and scintillation) are used to measure the intensity of the emitted beam. The flow
counter is commonly utilized for measuring long wavelength (>0.15 nm) X-rays that are
typical of K spectra from elements lighter than Zn. The scintillation detector is
commonly used to analyze shorter wavelengths in the X-ray spectrum (K spectra of
element from Nb to I; L spectra of Th and U). X-rays of intermediate wavelength (K
spectra produced from Zn to Zr and L spectra from Ba and the rare earth elements) are
generally measured by using both detectors in tandem. The intensity of the energy
measured by these detectors is proportional to the abundance of the element in the
sample. The exact value of this proportionality for each element is derived by
comparison to mineral or rock standards whose composition is known from prior
analyses by other techniques.
ApplicationsX-Ray fluorescence is used in a wide range of applications, including
research in igneous, sedimentary, and metamorphic petrology
soil surveys
mining (e.g., measuring the grade of ore)
cement production
ceramic and glass manufacturing
metallurgy (e.g., quality control)
environmental studies (e.g., analyses of particulate matter on air filters)
petroleum industry (e.g., sulfur content of crude oils and petroleum products)
field analysis in geological and environmental studies (using portable, hand-held
XRF spectrometers)
X-Ray fluorescence is particularly well-suited for investigations that involve
bulk chemical analyses of major elements (Si, Ti, Al, Fe, Mn, Mg, Ca, Na, K, P) in
rock and sediment
bulk chemical analyses of trace elements (in abundances >1 ppm; Ba, Ce, Co, Cr,
Cu, Ga, La, Nb, Ni, Rb, Sc, Sr, Rh, U, V, Y, Zr, Zn) in rock and sediment - detection
limits for trace elements are typically on the order of a few parts per million
X-ray fluorescence is limited to analysis of
relatively large samples, typically > 1 gram
materials that can be prepared in powder form and effectively homogenized
materials for which compositionally similar, well-characterized standards are
available
materials containing high abundances of elements for which absorption and
fluorescence effects are reasonably well understood
In most cases for rocks, ores, sediments and minerals, the sample is ground to a fine
powder. At this point it may be analyzed directly, especially in the case of trace element
analyses. However, the very wide range in abundances of different elements, especially
iron, and the wide range of sizes of grains in a powdered sample, makes the
proportionality comparison to the standards particularly troublesome. For this reason, it
is common practice to mix the powdered sample with a chemical flux and use a furnace
or gas burner to melt the powdered sample. Melting creates a homogenous glass that
can be analyzed and the abundances of the (now somewhat diluted) elements
calculated.
Strengths and Limitations of X-Ray Fluorescence (XRF)?
StrengthsX-Ray fluorescence is particularly well-suited for investigations that involve:
bulk chemical analyses of major elements (Si, Ti, Al, Fe, Mn, Mg, Ca, Na, K, P) in
rock and sediment
bulk chemical analyses of trace elements (>1 ppm; Ba, Ce, Co, Cr, Cu, Ga, La, Nb,
Ni, Rb, Sc, Sr, Rh, U, V, Y, Zr, Zn) in rock and sediment
LimitationsIn theory the XRF has the ability to detect X-ray emission from virtually all elements,
depending on the wavelength and intensity of incident x-rays. However...
In practice, most commercially available instruments are very limited in their
ability to precisely and accurately measure the abundances of elements with Z<11
in most natural earth materials.
XRF analyses cannot distinguish variations among isotopes of an element, so these
analyses are routinely done with other instruments (see TIMS and SIMS).
XRF analyses cannot distinguish ions of the same element in different valence
states, so these analyses of rocks and minerals are done with techniques such as
wet chemical analysis or Mossbauer spectroscopy.
User's Guide - Sample Collection and PreparationVirtually any solid or liquid material can be analyzed, if adequate standards are
available. For rocks and minerals, typical commercial instruments require a sample
constituting at least several grams of material, although the sample collected may be
much larger. For XRF chemical analyses of rocks, samples are collected that are several
times larger than the largest size grain or particle in the rock. This initial sample then
suffers a series of crushing steps to reduce it to an average grain size of a few
millimeters to a centimeter, when it can be reduced by splitting to a small
representative sample of a few tens to hundreds of grams. This small sample split is
then ground into a fine powder by any of a variety of techniques to create the XRF
sample. Care must be taken particularly at this step to be aware of the composition of
the crushing implements, which will inevitably contaminate the sample to some extent.
Data Collection, Results and Presentation
X-Ray spectrum
Data table
Detection limits
Precision
Accuracy
Database and Plotting
Evaluation of Data Quality (flyers, trends, discriminant fields)
Geochemical Plots
What is Scanning Electron Microscopy (SEM)
A typical SEM instrument, showing the electron column, sample chamber, EDS detector, electronics console, and visual
display monitors.
The scanning electron microscope (SEM) uses a focused beam of high-energy electrons
to generate a variety of signals at the surface of solid specimens. The signals that
derive from electron-sample interactions reveal information about the sample including
external morphology (texture), chemical composition, and crystalline structure and
orientation of materials making up the sample. In most applications, data are collected
over a selected area of the surface of the sample, and a 2-dimensional image is
generated that displays spatial variations in these properties. Areas ranging from
approximately 1 cm to 5 microns in width can be imaged in a scanning mode using
conventional SEM techniques (magnification ranging from 20X to approximately
30,000X, spatial resolution of 50 to 100 nm). The SEM is also capable of performing
analyses of selected point locations on the sample; this approach is especially useful in
qualitatively or semi-quantitatively determining chemical compositions (using EDS),
crystalline structure, and crystal orientations (using EBSD). The design and function of
the SEM is very similar to the EPMA and considerable overlap in capabilities exists
between the two instruments.
Fundamental Principles of Scanning Electron Microscopy (SEM)Accelerated electrons in an SEM carry significant amounts of kinetic energy, and this
energy is dissipated as a variety of signals produced byelectron-sample
interactions when the incident electrons are decelerated in the solid sample. These
signals include secondary electrons (that produce SEM images), backscattered electrons
(BSE), diffracted backscattered electrons (EBSD that are used to determine crystal
structures and orientations of minerals), photons (characteristic X-rays that are used for
elemental analysis and continuum X-rays), visible light (cathodoluminescence–CL), and
heat. Secondary electrons and backscattered electrons are commonly used for imaging
samples: secondary electrons are most valuable for showing morphology and
topography on samples and backscattered electrons are most valuable for illustrating
contrasts in composition in multiphase samples (i.e. for rapid phase discrimination). X-
ray generation is produced by inelastic collisions of the incident electrons with electrons
in discrete ortitals (shells) of atoms in the sample. As the excited electrons return to
lower energy states, they yield X-rays that are of a fixed wavelength (that is related to
the difference in energy levels of electrons in different shells for a given element). Thus,
characteristic X-rays are produced for each element in a mineral that is "excited" by the
electron beam. SEM analysis is considered to be "non-destructive"; that is, x-rays
generated by electron interactions do not lead to volume loss of the sample, so it is
possible to analyze the same materials repeatedly.
Scanning Electron Microscopy (SEM) Instrumentation - How Does It Work?
Essential components of all SEMs include the following:
Electron Source ("Gun")
Electron Lenses
Sample Stage
Detectors for all signals of interest
Display / Data output devices
Infrastructure Requirements:
o Power Supply
o Vacuum System
o Cooling system
o Vibration-free floor
o Room free of ambient magnetic and electric fields
SEMs always have at least one detector (usually a secondary electron detector), and
most have additional detectors. The specific capabilities of a particular instrument are
critically dependent on which detectors it accommodates.
Applications
The SEM is routinely used to generate high-resolution images of shapes of objects (SEI)
and to show spatial variations in chemical compositions: 1) acquiring elemental maps or
spot chemical analyses using EDS, 2)discrimination of phases based on mean atomic
number (commonly related to relative density) using BSE, and 3) compositional maps
based on differences in trace element "activitors" (typically transition metal and Rare
Earth elements) using CL. The SEM is also widely used to identify phases based on
qualitative chemical analysis and/or crystalline structure. Precise measurement of very
small features and objects down to 50 nm in size is also accomplished using the SEM.
Backescattered electron images (BSE) can be used for rapid discrimination of phases in
multiphase samples. SEMs equipped with diffracted backscattered electron detectors
(EBSD) can be used to examine microfabric and crystallographic orientation in many
materials.
Strengths and Limitations of Scanning Electron Microscopy (SEM)?
StrengthsThere is arguably no other instrument with the breadth of applications in the study of
solid materials that compares with the SEM. The SEM is critical in all fields that require
characterization of solid materials. While this contribution is most concerned with
geological applications, it is important to note that these applications are a very small
subset of the scientific and industrial applications that exist for this instrumentation.
Most SEM's are comparatively easy to operate, with user-friendly "intuitive" interfaces.
Many applications require minimal sample preparation. For many applications, data
acquisition is rapid (less than 5 minutes/image for SEI, BSE, spot EDS analyses.) Modern
SEMs generate data in digital formats, which are highly portable.
LimitationsSamples must be solid and they must fit into the microscope chamber. Maximum size in
horizontal dimensions is usually on the order of 10 cm, vertical dimensions are generally
much more limited and rarely exceed 40 mm. For most instruments samples must be
stable in a vacuum on the order of 10-5 - 10-6 torr. Samples likely to outgas at low
pressures (rocks saturated with hydrocarbons, "wet" samples such as coal, organic
materials or swelling clays, and samples likely to decrepitate at low pressure) are
unsuitable for examination in conventional SEM's. However, "low vacuum" and
"environmental" SEMs also exist, and many of these types of samples can be
successfully examined in these specialized instruments. EDS detectors on SEM's cannot
detect very light elements (H, He, and Li), and many instruments cannot detect
elements with atomic numbers less than 11 (Na). Most SEMs use a solid state x-ray
detector (EDS), and while these detectors are very fast and easy to utilize, they have
relatively poor energy resolution and sensitivity to elements present in low abundances
when compared to wavelength dispersive x-ray detectors (WDS) on most electron probe
microanalyzers (EPMA). An electrically conductive coating must be applied to
electrically insulating samples for study in conventional SEM's, unless the instrument is
capable of operation in a low vacuum mode.
User's Guide - Sample Collection and Preparation
Sample preparation can be minimal or elaborate for SEM analysis, depending on the
nature of the samples and the data required. Minimal preparation includes acquisition of
a sample that will fit into the SEM chamber and some accommodation to prevent charge
build-up on electrically insulating samples. Most electrically insulating samples are
coated with a thin layer of conducting material, commonly carbon, gold, or some other
metal or alloy. The choice of material for conductive coatings depends on the data to be
acquired: carbon is most desirable if elemental analysis is a priority, while metal
coatings are most effective for high resolution electron imaging applications.
Alternatively, an electrically insulating sample can be examined without a conductive
coating in an instrument capable of "low vacuum" operation.
Data Collection, Results and PresentationRepresentative SEM images of asbestiform minerals from the USGS Denver Microbeam
Laboratory
UICC Asbestos Chrysotile 'A' standard
Tremolite asbestos, Death Valley, California
Anthophyllite asbestos, Georgia
Winchite-richterite asbestos, Libby, Montana
What is Multicollector-Inductively Coupled Plasma Mass Spectrometer (MC-ICPMS)
Nu plasma MC-ICPMS. Details
MC-ICPMS is an instrument that measures isotopic ratios that are used in geochemistry,
geochronology, and cosmochemistry. A MC-ICPMS is a hybrid mass spectrometer that
combines the advantages of superior ionization of an inductively coupled plasma source
and the precise measurements of a magnetic sector multicollector mass spectrometer.
The primary advantage of the MC-ICPMS is its ability to analyze a broader range of
elements, including those with high ionization potential that are difficult to analyze by
TIMS. The ICP source also allows flexibility in how samples are introduced to the mass
spectrometer and allows the analysis of samples introduced either as an aspirated
solution or as an aerosol produced by laser ablation.
Fundamental Principles of Multicollector-Inductively Coupled Plasma Mass Spectrometer (MC-ICPMS)As a hybrid mass spectrometer, MC-ICPMS combines an inductively coupled plasma
(ICP) plasma source, an energy filter, a magnetic sector analyzer, and multiple
collectors for the measurement of ions. The ions are produced by introducing the
sample into an inductively coupled plasma which strips off electrons thereby creating
positively charged ions. These ions are accelerated across an electrical potential
gradient (up to 10 KV) and focused into a beam via a series of slits and electrostatically
charged plates. This ion beam then passes through an energy filter, which results in a
consistent energy spectrum in the ion beam and then through a magnetic field where
the ions are separated on the basis of their mass to charge ratio. These mass-resolved
beams are then directed into collectors where the ions reaching the collectors are
converted into voltage. Isotope ratios are calculated by comparing voltages from the
different collectors.
Multicollector-Inductively Coupled Plasma Mass Spectrometer (MC-ICPMS) Instrumentation - How Does It Work?
ThermoFinnigan MC-ICPMS. Details
Modern MC-ICPMS are composed of three primary components:
1. an inductively coupled plasma ion source, where ions are produced, accelerated,
and focused;
2. an analyzer, where a) the ions are focused and filtered to produce a beam where
the ions have the same approximate energy and can be separated based on their
mass/charge ratios; and
3. a series of collectors, where the ion beams are measured simultaneously.
The electronics of these instruments must operate to very close tolerances in order to
produce isotope ratios that are precise to 0.01-0.001%. In addition, a high vacuum
needs to be maintained along the path of the ion beam in order to avoid scattering of
the ions due to interaction with air molecules.
ApplicationsThe primary application of MC-ICPMS is to measure the isotopic ratios of elements used
in geochronologic/thermochronologic, radiogenic isotopic, and stable isotopic studies.
Geochronology/thermochronology refers to the use of radioactive decay to obtain the
time of a specific geologic event, which is referred to as an age. Tracer isotopic
applications use the natural isotopic variations in radiogenic isotopes due to decay of
radioactive elements. These isotopic variations can be used to evaluate the interaction
between geochemical systems and/or reservoirs. This application can also provide
general chronologic information, often referred to as model ages, which more loosely
constrain the timing of geologic processes and the development of, and interaction
between, geochemical reservoirs.
Separating elements on ion exchange columns in a clean laboratory. Details
For terrestrial systems, common applications in geochronology and tracer isotopic
studies involve the following isotopic systems
U-Th-Pb
Rb-Sr
Sm-Nd
Lu-Hf
Re-Os
U series disequilibrium
Sr, Nd, Hf, Os in seawater
In cosmochemistry, isotopic compositions are used to place constraints on
nucleosynthetic processes and the timing and evolution of solar system formation. This
involves use of the isotopic systems noted above, but also includes the use of extinct
radionuclides, which are nuclides that were formed during nucleosynthesis, but have
short half lives (generally < 100 m.y.) and are no longer naturally present in the solar
system. Their presence is detected by measuring isotopic variations in daughter
isotopes, as observed principally in meteorites. In addition to the systems noted above,
systems of cosmochemical interest include:
60Fe-60Ni
53Mn-53Cr
26Al-53Mg
107Pd-107Ag
92Nb-107Zr
146Sm-142Nd
182Hf-182W
Non-radiogenic (stable) isotope ratios are typically used to evaluate biologic and kinetic
processes and track reservoir interactions:
Li
B
Mg
Ca
Fe
Ni
Cu
Zn
Zr
Mo
Strengths and Limitations of Multicollector-Inductively Coupled Plasma Mass Spectrometer (MC-ICPMS)?
StrengthsThe advantages of MC-ICPMS compared to other isotope ratio techniques include:
- the ionization efficiency is very high (near 100%) for most elements which enables
analysis of most of the elements of the periodic table, including those with high
ionization potential that are difficult to analyze by TIMS
- the MC-ICPMS operates essentially as a steady state system during the analysis
resulting in time invariant mass fractionation
- there is consistent mass bias variation across the mass range which allows the use of
an adjacent element to calculate mass bias for those elements without > 2 stable
isotopes
- the MC-ICPMS permits flexibility in sample introduction systems. Solutions can be
introduced at atmospheric pressure, which allow ease in handling. Laser ablation
systems can also be coupled with the MC-ICPMS, which allows in-situ isotopic
measurements in solid materials (e.g., Hf isotopes in zircon).
LimitationsThe disadvantages of MC-ICPMS include:
- essentially all elements introduced into the plasma are ionized including doubly
charged species, oxides, and argides; in order to achieve the highest precision and
accuracy samples, need to be chemically purified (at least as pure as for TIMS).
- even with static multi-collection, plasma instability can limit precision
- even though ionization efficiency of the plasma is near 100%, transmission of ions is
lower than with TIMS because the plasma-generated ion must be transferred from
atmospheric pressure to the high vacuum of the mass spectrometer. Many ions are lost
during this difficult transfer.
- mass bias in a MC-ICPMS is not fully understood and may result from a combination of
factors, including sampling of ions in the plasma as well as during the formation of the
aerosol (from nebulizer or laser); as a result, traditional mass fractionation laws are
imperfect
- Although similar elements can be used to determine mass bias corrections in systems
with only two isotopes, (e.g., Yb for Lu; Tl for Pb) the mass bias response between the
two elements is not identical and must be accounted for
User's Guide - Sample Collection and PreparationAs for all geochemical analyses, care must be taken to preserve sample integrity from
the time of collection through analysis in all steps of physical and chemical preparation.
For the most accurate analysis, samples require complete dissolution followed by liquid
chromatography to isolate elements of interest and eliminate isobaric interferences. For
geochronologic and many tracer applications, it is necessary to "spike" with an
artificially enriched isotopic tracer in order to determine concentrations and parent-
daughter ratios by isotope dilution. For these applications, the sample is introduced as a
solution into a spray chamber that removes the majority of the liquid from the sample
and produces a fine aerosol that is injected into the plasma for ionization. The ICP
source also allows a laser to be interfaced with the instrument, which allows the
introduction of a laser generated aerosol into the plasma. This enables the in-situ
determination of isotopic ratios in certain materials enriched in the element of interest
(Sr isotopes in carbonates and plagioclase, Hf isotopes in zircon) and in some cases
allows the instrument to be used for depth profiling.
Data Collection, Results and Presentation
Lu-Hf garnet isochron with isotopic data generated by MC-ICPMS. Details
Measured isotope ratios must be properly corrected for all instrumental biases,
including mass fractionation. Once corrected, these ratios are suitable for plotting in
any diagrams requiring atomic ratios (e.g., isochron, concordia, etc.).
LiteratureThe following literature can be used to further explore Multicollector-Inductively Coupled
Plasma Mass Spectrometer (MC-ICPMS)
What is Thermal Ionization Mass Spectrometry (TIMS)
A TIMS is an instrument that measures isotopic ratios that are used in geochemistry,
geochronology, and cosmochemistry.
Fundamental Principles of Thermal Ionization Mass Spectrometry (TIMS)
A TIMS is a magnetic sector mass spectrometer that is capable of making very precise
measurements of isotope ratios of elements that can be ionized thermally, usually by
passing a current through a thin metal ribbon or ribbons under vacuum. The ions
created on the ribbon(s) are accelerated across an electrical potential gradient (up to 10
KV) and focused into a beam via a series of slits and electrostatically charged plates.
This ion beam then passes through a magnetic field and the original ion beam is
dispersed into separate beams on the basis of their mass to charge ratio. These mass-
resolved beams are then directed into collectors where the ion beam is converted into
voltage. Comparison of voltages corresponding to individual ion beams yield precise
isotope ratios.
Thermal Ionization Mass Spectrometry (TIMS) Instrumentation - How Does It Work?Modern instruments are composed of three primary components: 1) ion source, the
region in which ions are produced, accelerated, and focused; 2) analyzer, the region in
which the beam is separated based on mass/charge ratios; and 3) collector, a region in
which the ion beams are measured either sequentially (single collector) or
simultaneously (multi-collector). The electronics of these instruments must operate to
very close tolerances in order to produce isotope ratios that are precise to 0.01-0.001%.
ApplicationsThe primary application of TIMS is to measure the isotope ratios of elements used
ingeochronology and tracer studies. Geochronology refers to the use of radioactive
decay in closed systems to obtain the time of a specific geologic event, which is
referred to as an age. Tracer applications refer to the use of the growth of daughter
isotopes from radioactive decay to evaluate the interaction between geochemical
systems and/or reservoirs. This application provides only general chronologic
information, often referred to as model ages, which more loosely constrain the timing of
geologic processes and the development of, and interaction between, geochemical
reservoirs.
For terrestrial systems, common applications in geochronology and tracer Studies
involve the following radiometric systems
U-Th-Pb
Rb-Sr
Sm-Nd
Lu-Hf
Re-Os
U series disequilibrium
Sr, Nd, Hf, Os in seawater
In cosmochemical systems, the measurement of isotopic compositions is primarily as
tracers of nucleosynthetic processes and constraining the evolution of the solar system.
This involves measurement of the systems noted above, but also includes the decay of
short lived radionuclides, as observed principally in meteorites. In addition to the
systems noted above, systems of cosmochemical interest include:
Fe-Ni
Mn-Cr
Al-Mg
Zr-Mo
Mo-Ru
Non-radiogenic (stable) isotope-isotope ratios are typically used to characterize
exchange processes, track reservoir interactions, and evaluate biologic and kinetic
processes:
Li
B
Mg
Ca
Fe
Strengths and Limitations of Thermal Ionization Mass Spectrometry (TIMS)?
StrengthsThe advantage of TIMS compared to other isotope ratio techniques include:
the chemical and physical stability of the measurement environment, which lead
to highly precise measurements,
the ability to ionize and evaporate samples at different temperatures by using
multiple filament assemblies,
lower and more consistent average mass fractionation,
the use of single element solutions to eliminate isobaric interferences,
production of ions with a restricted range of energies (eliminates need for energy
filter),
easily automated operation, and
near 100% transmission of ions from source to collector.
LimitationsThe disadvantages include:
not all elements are easily ionized, which restricts applications to elements with
low ionization potentials;
ionization is not equally efficient for all elements, and is generally less than 1%;
mass fractionation continually changes during analysis;
elementally pure solutions are required to avoid isobaric interferences, which
requires extensive preparation; and
accurate mass fractionation correction is limited to elements with 3 or more
isotopes of which at least 2 are stable.
User's Guide - Sample Collection and PreparationAs for all geochemical analyses, care must be taken to preserve sample integrity from
the time of collection through analysis in all steps of physical and chemical preparation.
Most applications require complete dissolution of the sample followed by liquid
chromatography to isolate elements of interest, which is usually done in a "clean"
laboratory (typically Class 100-1000). For geochronologic and many tracer applications,
it is necessary to "spike" samples with an artificially enriched isotopic tracer in order to
determine concentrations and parent-daughter ratios by isotope dilution. Elements are
loaded directly as acid solutions on pre-cleaned metal ribbons for analysis.
Data Collection, Results and PresentationMeasured isotope ratios must be properly corrected for all instrumental biases,
including mass fractionation. Once corrected, these ratios are suitable for plotting in
any diagrams requiring atomic ratios (e.g., isochron, concordia, etc.) or for calculating
model ages and initial isotopic ratios.
LiteratureThe following literature can be used to further explore Thermal Ionization Mass
Spectrometry (TIMS)
Related LinksFor more information about Thermal Ionization Mass Spectrometry (TIMS) follow the
links below.
Thermal Ionization - this page, from the University of Arizona SAHRA program,
offers a brief description of thermal ionization.
Geochemistry of the World Wide Web - this site, from Cornell University, provides
links to geochemistry-related websites, including professional societies, journals,
on-line geochemical data, geochemical analytical standards, government and
university laboratories, and cosmochemistry-, astronomy-, and planetology-related
sites.
Mass Spectrometry Wiki - this Wiki site provides a brief description of thermal
ionization.
Thermo Scientific Corporation - this website provides details regarding the
perchase of a Triton thermal ionization ratio MS with multicollector.
Powerpoint tutorials on Mass Spectrometry from the EARTHTIME project.
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