Analisi di Fluorescenza X
a dispersione di energia
Tradizionale ed in Riflessione Totale
(EDXRF e TXRF)
The EM spectrum – X-Rays
400 keV
40 keV
1 keV
40 eV
Interactions of X-Rays with matter
Elastic (Rayleigh)
Scattering
X-ray Source
Photoelectric
absorption
Sample
Inelastic (Compton)
Scattering
X-ray fluorescence
Photoelectron
Incident photon
Fluorescence
photon
Competition: Auger effect
Photoelectron
Incident photon
Auger
electron
Fluorescence yield
1.0
Fluorescent Yield
Auger Electron Yield
0.8
K
0.6
1-K
L
0.4
1-L
0.2
0.0
0
20
40
60
Atomic Number Z
80
Transition probabilities
Germanium
2.4
18
2.2
16
2.0
counts/(channel second)
counts/(channel second)
X-Ray line families - K
1.8
1.6
Fe K
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
5000
6000
7000
8000
photon energy [eV]
9000
10000
14
12
Ag K
10
8
6
4
2
0
21000
22000
23000
24000
photon energy [eV]
25000
26000
X-Ray line families - L
5
counts / (channel second)
Pb L
4
3
2
1
0
8000
10000
12000
14000
photon energy [eV]
16000
Typical energy dispersive set-up
Pulse height
discriminator
ADC
TXRF and EDXRF geometries
TXRF
Conventional EDXRF
Energy-dispersive
detector
Energy-dispersive
detector
X-ray
tube
X-ray
tube
Primary
beam
Sample
Fluorescence
radiation
Fluorescence
radiation
Totally reflected
beam
Sample on
Optical flat
Comparison shows a difference in the geometric grouping of
excitation and detection units
The XRF quantification problem
Ni K
Cr K edge
6
7
8
Energy [keV]
absorption
enhancement
Ni K edge
Fe
Cr K
5
Cr
Fe
Ni
9
10
The XRF quantification problem
Monochromatic
Thin layer approximation
No dependence on other elements (matrix)
TXRF
EDX
detector
Incident
X-ray
beam
Reflected
X-ray
beam
Reflector
n (x-ray range ) = 1-  - i
 ~ 10-6
 ~ 10-8
 critical   2 
 critical
(Si, 17.5 keV) = 0.1°
= 1.75 mrad
• Thin sample layer deposited
on a reflector
• The total reflection effect
makes the sample support
“almost invisible”
TXRF basics
reflectivity, transmittivity
1.0
Quartz reflector
Mo K radiation
0.8
reflectivity
0.6
Incident
beam
transmittivity
Reflected
beam
0.4
0.2
0.0
Refracted
beam
0
1
4
3
2
incidence angle [mrad]
5
TXRF basics
2.0
1.8
Quartz reflector
Mo K radiation
Fluorescence
line
Arbitrary units
1.6
Background
1.4
1.2
Line intensity
IL  ( 1 + R )
1.0
Background
IB ( 1 - R ) sin
0.8
0.6
0.4
critical
angle
0.2
0.0
0.0
0.5
1.0
1.5
2.0
2.5
angle [mrad]
3.0
3.5
4.0
Detection limits
Rb
Mo
Counts / channel
scatter
2000
Background
DL  3
m ass
Net
Nb
0
15
20
Energy [keV]
Counts / channel
1500
1
DL 
tim e
1000
Nb
500
0
16.0
16.2
16.4
16.6
Energy [keV]
16.8
17.0
Easy quantification - Taking ratios
Internal standard – relative sensitivities
Compare with theory
CALIBRATE
QUANTIFY UNKNOWNS
Mo Ka - calibration curve
relative sensitivity to Ga
1
0.1
0.01
measured
fundamental parameters
Polynomial Fit of K data
Exp fit of L data
1E-3
1E-4
5
10
15
20
25
30
35
Z
50
60
70
80
90
Principle of TXRF
EDX
detector
ADVANTAGES
• Background reduction
• Double excitation of sample by
both the primary and reflected beam
• Small distance sample-detector
(~1mm) large solid angle
Incident
X-ray
beam
Reflected
X-ray
beam
Reflector
• Small sample volumes required
• Detection limits in the pg range with X-ray tube excitation
DISAVANTAGES
• Collimated beam required
• Sample preparation necessary for non liquid samples
Comparison between TXRF and EDXRF
spectrum
Main Advantages of TXRF
• No matrix effects
• A single internal standard
greatly simplifies quantitative
analyses
• Calibration and quantification
independent from any sample
matrix
• Simultaneous multi-element
ultra-trace analysis
• Several different sample types
and applications
• Minimal quantity of sample
required for the measurement
(5 µl)
• Unique micro analytical
applications for liquid and solid
samples
• Excellent detection limits (ppt
or pg) for all elements from
sodium to plutonium
• Excellent dynamic range from
ppt to percent
• Possibility to analyse the
sample directly without
chemical pre-treatment
• No memory effects
• Non destructive analysis
• Low running cost
The TXRF equipment
Main components:
• Double anode Mo/W X-ray tube
• Multilayer monochromator
MoK, WL/, Bremsstr.
• TXRF and EDXRF chambers
•High resolution Si(Li) detector
Front view
Back view
Minimum angular step
• monochromator
0.0074°
• tube shield
0.0016°
Alignment window
Control
• multilayer
• tube shield
Visualise
• X-ray line counts
• Total counts
The main features of the TX 2000 Spectrometer
• TXRF and EDXRF (traditional
45° geometry) spectroscopy in
the same equipment
• Automatic switching of primary
beam (MoK W/L and Bremsstrahlung 33 keV) using double
anode Mo/W X-ray tube, based on
innovative software. We select the
energy required using a high
reflectivity 80% (WL/L/MoK)
multilayer. We can choose also other
X-ray tubes and monochromatise the
energy that you need
• 3.8 liters UHV (Si(Li) 20 mm2
detector area) high resolution
detector <137 eV (K Mn radiation
at 5.89 keV), with an ultra-thin and
highly corrosion resistant window (8
mm Dura-Beryllium)
• Minimal distance between the
sample and the detector (mounted
to the axis normal plane of the
sample). In this position the
detector is also completely out of
the primary beam, as the angle
between the incident and the
reflected beams is so large
• Instrumental detection limits for
more than 50 elements below 10 pg
• Helium device to improve the
detection limits for the light
elements
• The spectrometer is fully
automated and you can control
different total reflection conditions
for different energies from the PC,
using stepping-motors moving
monochromator and tube shield and
MS Windows software.
Multielement standard - WL
6000
K
Zn
K
5000
L
counts/channel
L
4000
M
Cu
Ni
3000
Co
2000
Tl, Pb, Bi
1000
0
W L
scatter
Fe
Mn
Sr
Al Si
0
1
2
Cd
Ag
3
Cr
KCa
4
Ba
Ba
5
Ni
6
7
photon energy [keV]
8
Cu
9
10
Multielement standard - MoK
8000
K
7000
counts / channel
Sr
K
6000
L
5000
L
L
Ga
Zn
Cu
Tl
Ni
Pb
Bi
Co
Pb
Tl Bi
Fe
Mn
Cr
M
4000
3000
2000
Tl, Pb, Bi
1000
0
Si
Sr
Al
0
2
K
Ca
Ba
Ba
4
Zn
6
8
10
Mo
scatter
Sr
Pb Bi
12
14
photon energy [keV]
16
18
Multielement standard – 33keV
Ni
8000
lines
K K
Co
Fe
Mn
Cr
counts
6000
Multielement sample
10 ng Cd
W white spectrum
monochromatised at about 33 keV
load: 45 kV 20 mA; 500s
L L
K
Ca
4000
Zn
Cu
Ag
Cd
In
Zr
Sr
2000
W white spectrum
scattered radiation
Ga
Pb
Tl Bi Pb
Tl Bi Sr
Zr
Ag
Cd In
0
10
20
30
40
E (keV)
Elemental sensitivity periodic table
Excitation radiation
W-L Line
W-white Line
Mo-K Line
Detection Limits
< 5 pg
5-10 pg
10-30 pg
30-100 pg
>100 pg
Sample holder
A droplet of 10 µL is pipetted on a carrier with a diameter of 3 cm
The droplet leaves a dry residue after evaporation.
www.italstructures.com
isinfo@italstructures.com
Sample preparation scheme
Preparation of a TXRF measuring sample
Aliquotation
of some mL
Pipetting on
clean carrier
Addition of
some µL
internal
standard
Drying by
evaporation
Homogenization
by shaking
Taking off
some µL
Si(Li)-Detector
Measurement
Applications
•Environmental Analysis:
water, dust, sediment, aerosol
• Oils and greases: crude oil,
essential oil, fuel oil
• Medicine: toxic elements in
biological fluids and tissue
samples
• Pigments: ink, oil pants,
powder
• Forensic Science: analysis of
extremely small sample
quantities
• Pure chemicals: acids, bases,
salts, solvents, water, ultra
pure reagents
• Semiconductor Industry
(direct or after VPD-VPT)
• Nuclear Industry:
measurements of radioactive
elements
Spectrum of detection limits Chromium in distilled
water
Example of detection limits Chromium in distilled
water
Concentration
(ppb)
Volume µl
(5 x N)
Live Time
(seconds)
Detection
Limit (ppt)
Detection Limit
(pg) = ppt x
µl/1000
24.5
10 (5 x 2)
500
370
3.70
24.5
50 (5 x 10)
500
120
6.00
24.5
50 (5 x 10)
300
170
8.50
24.5* (spectr.)
100 (5 x 20)
500
70
7.00
24.5
100 (5 x 20)
1000
55
5.50
24.5
100 (5 x 20)
5000
35
3.50
1.97
10 (5 x 2)
500
400
4.00
1.97
10 (5 x 2)
300
440
4.40
1.97
50 (5 x 10)
500
80
4.00
1.97
50 (5 x 10)
300
125
6.25
Choice of the anode
counts / channel
Forensic: gunshot powder
Forensic: fiber analysis
800
black wool, acrylic and polyammide fiber
white cotton fiber
fiber from gray thermic gloves
counts
600
Zn
Mo
scattered radiation
Fe
Ca
400
Ti
Ni Cu
K
200
Si
Pb
S
Br Pb
Cr
Fe
Cl Ca
P
Ti
Ar
Cr Co
Zn
Ni
Cu
Rb
Sr
0
0
5
10
15
20
E(keV)
Figure 5
Food industry: wine
K
K
L
10000
L
counts/channel
Ca
S
1000
white wine
red wine
must
Ca
Cu
Fe
Ga
Rb
Mo K
40kV 30mA 500s
Mo
scatter
Ga int standard
Cl
white
Al
P
S
Cl
K
Ca
Mn
Fe
Ni
Cu
Zn
Br
Rb
Sr
Pb
600
Si
500
Zn
P
Sr
400
300
200
100
0
Cr
K
Mn
Pb
Pb
Rb
Zn
Al
0
2
4
6
8
10 12 14
photon energy [keV]
16
18
20
8.718
1.355
1.956
20.674
0.063
0.057
0.006
0.142
0.011
red
must
9.397
41.987
162.824
6.144
31.139 20.424
691.89 709.589
53.741
29.24
0.875
0.299
4.39
0.392
0.02
0.081
9.049
0.507
0.606
0.172
1.547
0.544
0.577
0.025
Industrial application case study:
Petrochemical transformation
Process assistance and quality control
Monitor corrosion phenomena
and possibly give indications on
the origin (Fe, Ni, Cr, Mn)
Individuate transport processes of
elements deriving for catalyst (Co,
Ni, Pt, Rh, Cr, Cu, …)
Logistics
• Search the probable causes of deterioration (contamination) of the products
during Transport and Stocking – Reflects on product price and on logistic costs
(e.g. ship stop)
Applications


Raw materials for intermediate
products
Intermediate compounds for the
synthesis of final products
destined to high consumption
markets
Cosmetics
Detergents
Lubrication
Paper Industry
Plastics
Food industry
Leather industry
The limits for the metals content are regulated by different norms,
mostly dictated by Acceptance Specifications of the client.
Olefin C10-13
70 ppb
17 ppb
Ctz.: Pt, Ni
Conc.
(ppm)
ICP
TXRF
Ca
Cd
Co
Cr
Cu
Fe
Mn
Mo
Ni
Pb
Rh
Sn
Sr
V
Zn
0.36
<0.004
<0.002
0.003
0.006
0.08
<0.001
<0.008
0.015
<0.04
<0.03
0.02
<0.0003
<0.002
0.07
0.45
<0.015
<0.005
<0.005
0.006
0.07
<0.003
<0.007
0.017
<0.002
<0.008
<0.019
<0.002
<0.008
0.06
Linear paraffin C10-13
50 ppb
8 ppb
Conc.
(ppm)
ICP
TXRF
Ca
Cd
Co
Cr
Cu
Fe
Mn
Mo
Ni
Pb
Rh
Sn
Sr
V
Zn
0.18
0.009
0.003
0.013
0.008
0.07
0.003
<0.008
0.009
<0.04
<0.03
<0.008
<0.001
<0.002
0.04
0.13
<0.015
<0.005
0.006
0.008
0.05
0.00
<0.007
0.003
<0.002
<0.008
<0.019
<0.002
<0.008
0.00
Detection limits: ICP-OES vs. TXRF
0.045
0.040
ICP
0.035
ppm
0.030
TXRF
0.025
0.020
0.015
0.010
0.005
0.000
Ca
V
Cr
ICP-OES (ASTM: D 5708-B)
Campione : 10g @ 25 ml
Mn
Fe
Ni
Co
Cu
Zn
Sr
Mo
Rh
Cd
Sn
Pb
Correlation ICP-OES vs. TXRF
ICP-OES vs. TXRF
 Paired t-test : results do
0.8

TXRF (ppm)
0.6
0.4
0.2
0.0
0.0
0.2
0.4
ICP OES (ppm)
0.6
0.8
not differ significantly
Linearly correlated
Y=A+B*X
N = 32
R = 0.998
-------------------------------------Param
Value
IC (t*s)
-------------------------------------A
-0.0039
0.0046
B
1.0137
0.0252
-------------------------------------
Conclusions
ICP-OES
TXRF
Sensitivity
Comparable, except for Rh
and Pb
Decreases with atomic
number
Sample
preparation
Time consuming treatment
(days) with risk of
contamination
Simple and fast
Time
3-4 days
A few hours (about 3)
Calibration
Multielement: depending
on the element to be
determined
ONE ONLY
internal standard
Field of
application
"non volatile” metals (no
Hg, Se, As..)
Simultaneous and
accurate determination of
the elements with Z > 15
Environmental: soil
Microwave mineralisation in
10 ml HNO3. Final volume 50 ml
K
10000
K
Si
S
120
Mo
scatter
L
L
Fe
Ca
1000
Ga
Rb
Mn
Sr
Rb
Ca
100 Al
Fe escape
counts/channel
K
Fe
80
60
40
As
Ga Pb
Ni
Zn
Cu
Pb
20
0
2
4
6
8
10 12 14
photon energy [keV]
16
18
Environmental: gasoline
Ga K 15 ppm
standard interno
Internal
standard
1400
Conteggi
Counts
1200
Sorgente di Mo 35 kV, 30 mA
X-ray tube 35kV, 30mA
10  L diMo
campione
Sample: 10 µL
Tempo di
conteggio 200 s.
Live time: 200 s
Benzina Standard ICIP Pb 0.324 g/l
Standard Petrol ICP Pb 0.324 g/l
1000
Pb
Pb
800
600
400
Ga K
S
200
Si
0
0
Mo
radiazione
scatterata
Scattered
radiation
V
Pb
5
10
Pb
Pb
15
20
E (keV)
Environmental: compost
microwave
microwave
TXRF no treatment
ARPAVRING_3-02: esercizio di interconfronto
Particulate matter monitoring
Multi-stage Cascade impactors can be used
in order to collect the the particulate matter
onto standard quartz carriers that can be
analysed directly with the TXRF without any
sample preparation.
Comparison of Important Analytical Features of
the Three Competitive Methods
Analytical Features
ICP-MS
TXRF
INAA
Samples
Volume or mass
2-5 mL
5-50 µL
10-200 mg
Preparation of solid
Digestion or suspension
Digestion or suspension
None
Dissolvation portion
< 0.4%
< 1%
Any
Diluition of acids
1:100
None
None
Consumption
Yes
No
No
Detection limits
Excellent
Very good
Very good
Element limitations
H, C, N, O, F, P, S
Z < 13
Z < 9; Tl, Pb, Bi
Spectral interferences
Several
Few
Few
Isotope detection
Yes
No
No
Calibration
Several external and
internal standards
One internal standard
Some pure element foils
Matrix effects
Severe
None
None
Memory effects
Yes
No
No
Time consumption
< 3 min
< 20 min
20 min – 30 days
Equipment
Ar-plasma + quadrupole
MS
Special EDS
Nuclear reactor + spectrometer
Capital costs
Medium
Medium
Very high
Running costs
High
Low
High
Maintenance
Frequently
Seldom
Seldom
Detection
Quantification
Expenditure
Benefits and Drawbacks of TXRF Applied to
Element Analyses
Benefits:
Drawbacks or limitations:
• Unique micro analytical capability
• Impossibility of totally nondestructive analysis
• Great variety of samples and
applications
• Limitation for non-volatile liquids
• Simultaneous multielement
determination
• Exception of low-Z elements
• Low detection limits
• Restriction to flat or polished
samples
• Simple quantification by internal
standardization
• No matrix or memory effects
• Wide dynamic range
• Non-destructive surface and thinlayer analysis
• Simple automated operations
• Low running costs and
maintenance
• Limitation by high matrix contents
References
R. Klockenkämper, Total-Reflection X-Ray Fluorescence Analysis,
John Wiley and Sons Inc., New York, 1997, ISBN 0-471-30524-3
Spectrochimica Acta Part B: Atomic Spectroscopy
TXRF Special Issues – TXRF conference proceedings
Vol.
Vol.
Vol.
Vol.
Vol.
Vol.
Vol.
44,
46,
48,
52,
54,
56,
58,
Issue
Issue
Issue
Issue
Issue
Issue
Issue
5
10
2
7
10
11
12
(1989)
(1991)
(1993)
(1997)
(1999)
(2001)
(2003)
References
Handbook of X-Ray Spectrometry
Rene E. Van Grieken
Andrzej A. Markowicz
ISBN: 0824706005
Publisher: Marcel Dekker
Total Reflection XRF (TXRF), P.Kregsamer, C.Streli, P.Wobrauschek,
Book chapter "Handbook of X-ray Spectrometry",
Ed: R.Van Grieken, A.Markowicz, Marcel Dekker, 2002
Total Reflection X-ray Fluorescence Analysis,
P.Wobrauschek, C.Streli, Chapter in :
Encyclopedia of Analytical Chemistry,
Ed.:R.A.Meyers,
Wiley & Sons, 2000, 13384-13414