x ray flouresence analysis (xrf). xrf x-ray fluorescence is used to identify and measure the...
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X Ray Flouresence Analysis(XRF)
XRFXRF
X-Ray Fluorescence
is used to identify and measure the
concentration of
elements in a sample
X-Ray Fluorescence
is used to identify and measure the
concentration of
elements in a sample
XRF instrumental parameters
• x-ray tube kv
• x-ray tube mA
• primary beam filters
• collimator masks
• x-ray tube kv
• x-ray tube mA
• primary beam filters
• collimator masks
• collimator
• crystal
• detector
• path
• collimator
• crystal
• detector
• path
Sampel
METAL POWDER LIQUID
XRF onlyXRD and XRF
XRF Working ConceptXRF Working Concept
In X-ray fluorescence spectroscopy, the process begins by exposing the sample to a source of x-rays. As these high energy photons strike the sample, they tend to knock electrons out of their orbits around the nuclei of the atoms that make up the sample. When this occurs, an electron from an outer orbit, or “shell”, of the atom will fall into the shell of the missing electron. Since outer shell electrons are more energetic than inner shell electrons, the relocated electron has an excess of energy that is expended as an x-ray fluorescence photon. This fluorescence is unique to the composition of the sample. The detector collects this spectrum and converts them to electrical impulses that are proportional to the energies of the various x-rays in the sample’s spectrum.
Factor of errors in Sample Preparation
Grain size and surface roughnessUniformity of sampleContamination through the sample preparation
Grain size and surface roughness
Uniformity of sample
Metallic Sample
Casting condition of the sample in the molding.
Sand molding
Metal molding
X-ray intensities differ according to the molding method which comesIn the measurement of light elements.
Quenching casting which makes the metallic composition fine produces good results
Sample polishing
NiK intensity CrK intensity
50# emery paper 0.686 0.974
100# emery paper 0.699 0.983
240# emery paper 0.704 0.989
Mirror polishing 0.709 0.993
Uniformity of sample
Contamination during polishing
Contamination effect when carbon steel and Ni-Cr alloy polish after polishing stainless steel.
As the contamination form the polishing belt to the sample, the re contamination fromThe material of the polishing belt and from the remaining trace elements of polishedSample.
Ni Cr Fe
% Conc 0.55 0.21 2.10
% Contamination 0.05 0.03 0.38
Powder SampleGrinding Condition
Different grinding condition cause variation in particle size distribution whichleads to variation in X-Ray intensity.
user benefits of wavelength dispersive XRF
• versatile
• accurate
• reproducible
• fast
• non destructive
• versatile
• accurate
• reproducible
• fast
• non destructive
XRF is versatileXRF is versatile
element range is Be to U
atomic numbers (Z) of 4 to 92
concentration range covers 0.1 ppm to 100 %
samples can be in the form of solids, liquids, powders or fragments
element range is Be to U
atomic numbers (Z) of 4 to 92
concentration range covers 0.1 ppm to 100 %
samples can be in the form of solids, liquids, powders or fragments
XRF is accurateXRF is accurate
generally better than 1 % relative
(i.e. 10% ± 0.1%)
accuracy is limited by calibration
standards, sample preparation,
sample matrix, sampling,
instrumental errors & statistics
generally better than 1 % relative
(i.e. 10% ± 0.1%)
accuracy is limited by calibration
standards, sample preparation,
sample matrix, sampling,
instrumental errors & statistics
XRF is reproducibleXRF is reproducible
generally within 0.1% relative
good reproducibility requires high
quality mechanics, stable electronics
and careful construction techniques
generally within 0.1% relative
good reproducibility requires high
quality mechanics, stable electronics
and careful construction techniques
XRF is fastXRF is fast
counting times generally between 1 & 50 seconds for each element
semi-quant analysis of all matrix elements in 10 to 20 minutes
overnight un-attended operation
counting times generally between 1 & 50 seconds for each element
semi-quant analysis of all matrix elements in 10 to 20 minutes
overnight un-attended operation
XRF is non-destructiveXRF is non-destructive
• standards are permanent
• measured samples can be stored and
re-analysed at a later date
• precious samples are not damaged
• standards are permanent
• measured samples can be stored and
re-analysed at a later date
• precious samples are not damaged
properties of x-rays
the following four slides list some
of the more important properties
of x-rays that contribute to the
nature of XRF analysis
XRF analytical envelope
elemental range
detection limits
analysis times
accuracy
reproducibility
elemental range
beryllium (4) to uranium (92)
in solids
fluorine (9) to uranium (92)
in liquids
range of elements in solid samples are shown in green (Be to U)
range of elements in liquid samples are shown in green (Na to U)
detection limits (LLD)
function of atomic number (Z) & the mix of elements within the sample
(sample matrix) < 1 ppm for high Z in a light matrix
(e.g. Pb in petrol) or > 10 ppm for low Z in a heavy
matrix (Na in slag)
XRF applications summary
• Na to U in all sample types
• Be to U in solid samples
• accuracy generally 0.1 to 1 % relative
• reproducibility typically < 0.5% relative
• typical LLD is normally 1 - 10 ppm (depends on element being measured and
the sample matrix)
XRF errors
the following section describes
major source of errors in XRF
analysis, and investigates how
these errors can be minimized to
achieve maximize accuracy
overview of XRF methodologyoverview of XRF methodology
good accuracy requires• careful sample preparation
• fused beads for light elements• accurate standards
• selection of optimum instrument parameters
• collection of enough counts to avoid statistical errors
Methods of Analysis
the following presentation
describes the requirements for
quantitative and semi-quantitative
analysis
XRF analytical methods
the atomic number (Z) of each of the
elements to be determined will have
an influence on the type of sample
preparation to be used, and the
quantitative or semi-quantitative
method that will be the most suitable
XRF analytical methods
the quantitative method is the most accurate, but requires
calibration standards
semi-quantitative method is less accurate, but does not require
standards
the quantitative method is the most accurate, but requires
calibration standards
semi-quantitative method is less accurate, but does not require
standards
overview of XRF methodologyoverview of XRF methodology
elements to be measured
• low Z will require careful preparation
• low Z may have lower accuracy
• low Z may require fusion of powders
• semi-quant does not measure the very light elements (Be to N)
overview of XRF methodology
concentration ranges
as the concentration range for each element increased, accuracy
generally decreases
large concentration ranges will require more standards
XRF applications summary
• Na to U in all sample types
• Be to U in solid samples
• accuracy typically 0.1 to 1 % relative
• typical LLD is between 1 - 10 ppm
Thank you for your attending!
Workshop & Analysis Informations:
Dr. Sayekti Wahyuningsih, M.SiCandra Purnawan, M.Sc
Laboratorium MIPA Terpadu FMIPA Universitas Sebelas MaretPhone / fax : (0271) 663375