x ray flouresence analysis (xrf). xrf x-ray fluorescence is used to identify and measure the...

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