Analisi di Fluorescenza X a dispersione di energia

Tradizionale ed in Riflessione Totale(EDXRF e TXRF)

40 eV

400 keV

1 keV

40 keV

The EM spectrum – X-RaysThe EM spectrum – X-Rays

Interactions of X-Rays with matterInteractions of X-Rays with matter

X-ray Source Sample

Photoelectricabsorption

Elastic (Rayleigh)Scattering

Inelastic (Compton)Scattering

Incident photon

X-ray fluorescenceX-ray fluorescence

Photoelectron

Fluorescencephoton

Incident photon

Competition: Auger effectCompetition: Auger effect

Photoelectron

Augerelectron

Fluorescence yieldFluorescence yield

0 20 40 60 800.0

0.2

0.4

0.6

0.8

1.0

ωK 1-ωK ωL 1-ωL

Fluorescent Yield

Auger Electron Yield

Atomic Number Z

Transition probabilitiesTransition probabilities

Germanium

X-Ray line families - KX-Ray line families - K

5000 6000 7000 8000 9000 100000.00.20.40.60.81.01.21.41.61.82.02.22.4

counts

/(ch

annel

sec

ond)

photon energy [eV]

Fe K

21000 22000 23000 24000 25000 260000

2

4

6

8

10

12

14

16

18

counts

/(ch

annel

sec

ond)

photon energy [eV]

Ag K

8000 10000 12000 14000 160000

1

2

3

4

5

counts

/ (

chan

nel

sec

ond)

photon energy [eV]

X-Ray line families - LX-Ray line families - L

Pb L

Typical energy dispersive set-upTypical energy dispersive set-up

ADC

Pulse heightdiscriminator

X-raytube

Primarybeam

Fluorescenceradiation

Sample

Energy-dispersivedetector

Conventional EDXRFConventional EDXRF

X-raytube

Sample onOptical flat

Fluorescenceradiation

Energy-dispersivedetector

Totally reflectedbeam

TXRFTXRF

Comparison shows a difference in the geometric grouping ofexcitation and detection units

Comparison shows a difference in the geometric grouping ofexcitation and detection units

TXRF and EDXRF geometriesTXRF and EDXRF geometries

5 6 7 8 9 10

Ni K edge

Ni Kα

Fe

Cr K edge

Cr Kα

Cr Fe Ni

Energy [keV]

enhancement

absorption

The XRF quantification problemThe XRF quantification problem

The XRF quantification problemThe XRF quantification problem

Monochromatic

Thin layer approximationThin layer approximation

No dependence on other elements (matrix)

TXRFTXRF

EDXdetector

Incident X-ray beam

ReflectedX-raybeam

Reflector

• Thin sample layer deposited on a reflector• The total reflection effect makes the sample support “almost invisible”

n (x-ray range ) = 1- δ - iβ

δ ~ 10-6β ~ 10-8

ϕ critical ≈ √ 2 δ

ϕ critical(Si, 17.5 keV) = 0.1°

= 1.75 mrad

TXRF basicsTXRF basics

0 1 2 3 4 50.0

0.2

0.4

0.6

0.8

1.0

reflec

tivi

ty,

tran

smittivi

ty

incidence angle [mrad]

reflectivity

transmittivity

Quartz reflectorMo Kα radiation

Incidentbeam

Reflectedbeam

Refractedbeam

TXRF basicsTXRF basics

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.00.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

criticalangle

Background

Fluorescenceline

Arbitrary units

angle [mrad]

Line intensityIL∝ ( 1 + R )

BackgroundIB∝ ( 1 - R ) sinφ

Quartz reflectorMo Kα radiation

15 200

2000

scatter

Mo

Nb

Rb

Cou

nts

/ cha

nnel

Energy [keV]

massNet

BackgroundDL 3=

timeDL 1∝

Detection limitsDetection limits

16.0 16.2 16.4 16.6 16.8 17.00

500

1000

1500

Nb

Cou

nts

/ cha

nnel

Energy [keV]

Easy quantification - Taking ratiosEasy quantification - Taking ratios

Internal standard – relative sensitivitiesInternal standard – relative sensitivities

CALIBRATE

QUANTIFY UNKNOWNS

Compare with theory

Mo Ka - calibration curveMo Ka - calibration curve

5 10 15 20 25 30 35 50 60 70 80 901E-4

1E-3

0.01

0.1

1

rela

tive

sens

itivi

ty to

Ga

Z

measured fundamental parameters Polynomial Fit of Kα data Exp fit of Lα data

Principle of TXRFPrinciple of TXRF

EDXdetector

Incident X-ray beam

ReflectedX-raybeam

Reflector

ADVANTAGESADVANTAGES

• Background reduction• Background reduction

• Double excitation of sample by both the primary and reflected beam• Double excitation of sample by both the primary and reflected beam

• Small distance sample-detector(~1mm) large solid angle• Small distance sample-detector(~1mm) large solid angle

• Small sample volumes required• Small sample volumes required

• Detection limits in the pg range with X-ray tube excitation• Detection limits in the pg range with X-ray tube excitation

DISAVANTAGESDISAVANTAGES

• Collimated beam required• Collimated beam required

• Sample preparation necessary for non liquid samples• Sample preparation necessary for non liquid samples

Comparison between TXRF and EDXRF spectrum

Comparison between TXRF and EDXRF spectrum

Main Advantages of TXRFMain Advantages of TXRF

• No matrix effects• No matrix effects

• A single internal standard greatly simplifies quantitative analyses

• A single internal standard greatly simplifies quantitative analyses• Calibration and quantification independent from any sample matrix

• Calibration and quantification independent from any sample matrix• Simultaneous multi-element ultra-trace analysis• Simultaneous multi-element ultra-trace analysis• Several different sample types and applications• Several different sample types and applications• Minimal quantity of sample required for the measurement (5 µl)

• Minimal quantity of sample required for the measurement (5 µl)

• Unique micro analytical applications for liquid and solid samples

• Unique micro analytical applications for liquid and solid samples• Excellent detection limits (pptor pg) for all elements from sodium to plutonium

• Excellent detection limits (pptor pg) for all elements from sodium to plutonium• Excellent dynamic range from ppt to percent• Excellent dynamic range from ppt to percent• Possibility to analyse the sample directly without chemical pre-treatment

• Possibility to analyse the sample directly without chemical pre-treatment• No memory effects• No memory effects

• Non destructive analysis• Non destructive analysis

• Low running cost• Low running cost

The TXRF equipmentThe TXRF equipment

Main components:• Double anode Mo/W X-ray tube• Multilayer monochromator

MoKα, WLα/β, Bremsstr.• TXRF and EDXRF chambers•High resolution Si(Li) detector

Front viewFront view

Back viewBack view

Minimum angular step

• monochromator 0.0074°

• tube shield 0.0016°

Alignment windowAlignment window

Control

• multilayer

• tube shield

Visualise

• X-ray line counts

• Total counts

• TXRF and EDXRF (traditional45° geometry) spectroscopy inthe same equipment

• TXRF and EDXRF (traditional45° geometry) spectroscopy inthe same equipment

• Automatic switching of primary beam (MoKα W/Lα and Brems-strahlung 33 keV) using double anode Mo/W X-ray tube, based on innovative software. We select the energy required using a high reflectivity 80% (WLα/Lβ/MoKα) multilayer. We can choose also other X-ray tubes and monochromatise the energy that you need

• Automatic switching of primary beam (MoKα W/Lα and Brems-strahlung 33 keV) using double anode Mo/W X-ray tube, based on innovative software. We select the energy required using a high reflectivity 80% (WLα/Lβ/MoKα) multilayer. We can choose also other X-ray tubes and monochromatise the energy that you need• 3.8 liters UHV (Si(Li) 20 mm2detector area) high resolution detector

Multielement standard - WLβMultielement standard - WLβ

0 1 2 3 4 5 6 7 8 9 100

1000

2000

3000

4000

5000

6000

counts

/channel

photon energy [keV]

Zn

CuNi

Co

FeMn

Cr

KCaBa

Ba

Tl, Pb, Bi

Al SiSr

Kα

Kβ

Lα

Lβ

M

CuNiAgCd

W Lβscatter

0 2 4 6 8 10 12 14 16 180

1000

2000

3000

4000

5000

6000

7000

8000

counts

/ c

han

nel

photon energy [keV]

Sr

GaZn

CuNi

CoFe

MnCr

KCa

Moscatter

TlPb

Bi

Tl BiPb

Sr

BaBa

Tl, Pb, Bi

ZnAl

SiSr

PbBi

Kα

Kβ

Lα

Lβ

Lγ

M

Multielement standard - MoKαMultielement standard - MoKα

Multielement standard – 33keVMultielement standard – 33keV

10 20 30 400

2000

4000

6000

8000 lines

LβLα

KβKα Multielement sample10 ng CdW white spectrum monochromatised at about 33 keVload: 45 kV 20 mA; 500s

TlBiTl

PbBi Pb

CrMnFeCo

Ni

Cu

Zn

Ga

Ca

K

Sr

In

Zr

ZrSr Ag

Cd

Cd

In

Ag

W white spectrumscattered radiation

counts

E (keV)

Excitation radiation

W-L LineW-white Line

Mo-K Line

< 5 pg 5-10 pg 10-30 pg 30-100 pg >100 pg

Detection Limits

Elemental sensitivity periodic tableElemental sensitivity periodic table

isinfo@italstructures.comwww.italstructures.com

A droplet of 10 µL is pipetted on a carrier with a diameter of 3 cmThe droplet leaves a dry residue after evaporation.

A droplet of 10 µL is pipetted on a carrier with a diameter of 3 cmThe droplet leaves a dry residue after evaporation.

Sample holderSample holder

Sample preparation schemeSample preparation scheme

Preparation of a TXRF measuring samplePreparation of a TXRF measuring sample

Aliquotationof some mL

Addition ofsome µLinternalstandard

Homogenizationby shaking

Taking offsome µL

Pipetting onclean carrier

Drying byevaporation

Measurement

Si(Li)-Detector

ApplicationsApplications

•Environmental Analysis: water, dust, sediment, aerosol•Environmental Analysis: water, dust, sediment, aerosol

• Medicine: toxic elements in biological fluids and tissue samples

• Medicine: toxic elements in biological fluids and tissue samples

• Forensic Science: analysis of extremely small sample quantities

• Forensic Science: analysis of extremely small sample quantities

• Pure chemicals: acids, bases, salts, solvents, water, ultra pure reagents

• Pure chemicals: acids, bases, salts, solvents, water, ultra pure reagents

• Oils and greases: crude oil, essential oil, fuel oil• Oils and greases: crude oil, essential oil, fuel oil

• Pigments: ink, oil pants, powder• Pigments: ink, oil pants, powder

• Semiconductor Industry(direct or after VPD-VPT)• Semiconductor Industry(direct or after VPD-VPT)

• Nuclear Industry: measurements of radioactive elements

• Nuclear Industry: measurements of radioactive elements

Spectrum of detection limits Chromium in distilled water

Spectrum of detection limits Chromium in distilled water

Example of detection limits Chromium in distilled water

Example of detection limits Chromium in distilled water

6.2512530050 (5 x 10)1.97

4.008050050 (5 x 10)1.97

4.4044030010 (5 x 2)1.97

4.0040050010 (5 x 2)1.97

3.50355000100 (5 x 20)24.5

5.50551000100 (5 x 20)24.5

7.0070500100 (5 x 20)24.5* (spectr.)

8.5017030050 (5 x 10)24.5

6.0012050050 (5 x 10)24.5

3.7037050010 (5 x 2)24.5

Detection Limit (pg) = ppt x

µl/1000

Detection Limit (ppt)

Live Time(seconds)

Volume µl(5 x N)

Concentration (ppb)

Choice of the anodeChoice of the anode

Forensic: gunshot powderForensic: gunshot powder

coun

ts /

chan

nel

0 5 10 15 200

200

400

600

800

Fi 5

counts

Pb

Pb

SrRb

Br

Ni CuZn

Zn

CuNi

CoFe

Fe

Cr

CrTi

Ti

Ca

Ca

K

ArCl

S

P

Si

Moscattered radiation

black wool, acrylic and polyammide fiber white cotton fiber fiber from gray thermic gloves

E(keV)

Forensic: fiber analysisForensic: fiber analysis

Food industry: wineFood industry: wine

0 2 4 6 8 10 12 14 16 18 200

100

200

300

400

500

600

1000

10000

counts

/channel

photon energy [keV]

white wine red wine must

Mo Kα40kV 30mA 500s

Ga int standard

white red mustAl 9.397P 41.987S 8.718 162.824 6.144Cl 1.355 31.139 20.424K 1.956 691.89 709.589

Ca 20.674 53.741 29.24Mn 0.875 0.299Fe 0.063 4.39 0.392Ni 0.02Cu 0.081 9.049Zn 0.057 0.507 0.606Br 0.006 0.172Rb 1.547 0.544Sr 0.142 0.577Pb 0.011 0.025

RbGa

Zn

CuFe

MnCr

K

Ca

Moscatter

Pb

Pb

ZnAl

Kα

Kβ

Lα

Lβ

SrSi

Ca

P

S

Cl

Rb

Industrial application case study:Petrochemical transformation

Industrial application case study:Petrochemical transformation

Monitor corrosion phenomena and possibly give indications on the origin (Fe, Ni, Cr, Mn)

Process assistance and quality control

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)

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.

ApplicationsApplications

Olefin C10-13Olefin C10-13

Conc. (ppm) ICP TXRF

Ca 0.36 0.45Cd

Linear paraffin C10-13Linear paraffin C10-13

Conc. (ppm) ICP TXRF

Ca 0.18 0.13Cd 0.009

Detection limits: ICP-OES vs. TXRFDetection limits: ICP-OES vs. TXRF

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

0.040

0.045

Ca V Cr Mn Fe Ni Co Cu Zn Sr Mo Rh Cd Sn Pb

ppm

ICP

TXRF

ICP-OES (ASTM: D 5708-B)Campione : 10g @ 25 ml

Correlation ICP-OES vs. TXRFCorrelation ICP-OES vs. TXRF

0.0 0.2 0.4 0.6 0.8

0.0

0.2

0.4

0.6

0.8

TXR

F (p

pm)

ICP OES (ppm)

ICP-OES vs. TXRFPaired t-test : results do not differ significantlyLinearly correlated

Y = A + B * X N = 32 R = 0.998 --------------------------------------Param Value IC (t*s)--------------------------------------A -0.0039 0.0046B 1.0137 0.0252-------------------------------------

ICP-OES TXRF

Sensitivity Comparable, except for Rh and PbDecreases with atomic

number

Sample preparation

Time consuming treatment (days) with risk of

contaminationSimple and fast

Time 3-4 days A few hours (about 3)

CalibrationMultielement: 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

ConclusionsConclusions

Environmental: soilEnvironmental: soil

0 2 4 6 8 10 12 14 16 18

20

40

60

80

100

120

1000

10000

counts

/chan

nel

photon energy [keV]

Sr

Ga

ZnCu

Ni

Fe

Mn

K

Ca

Moscatter

Pb

Pb

Rb

Al

Kα

Kβ

Lα

Lβ

Rb

Fe

Ca

Si S

Fe e

scap

e GaAs

Microwave mineralisation in10 ml HNO3. Final volume 50 ml

0 5 10 15 200

200

400

600

800

1000

1200

1400

Sorgente di Mo 35 kV, 30 mA10 μL di campioneTempo di conteggio 200 s.

Benzina Standard ICIP Pb 0.324 g/l

PbPbPb

Pb

Pb

Moradiazione scatterata

Ga Kβ

Ga Kα 15 ppmstandard interno

VS

Si

Conteggi

E (keV)

Counts

Standard Petrol ICP Pb 0.324 g/l

Internal standard

Scattered radiation

Mo X-ray tube 35kV, 30mASample: 10 µLLive time: 200 s

Environmental: gasolineEnvironmental: gasoline

Environmental: compostEnvironmental: compost

microwave

microwaveTXRF no treatment

ARPAVRING_3-02: esercizio di interconfronto

Particulate matter monitoringParticulate matter monitoring

Multi-stage Cascade impactors can be usedin order to collect the the particulate matter onto standard quartz carriers that can be analysed directly with the TXRF without anysample preparation.

SeldomSeldomFrequentlyMaintenance

HighLowHighRunning costs

Very highMediumMediumCapital costs

Nuclear reactor + γ-spectrometer

Special EDSAr-plasma + quadrupoleMS

Equipment

Expenditure

20 min – 30 days< 20 min< 3 minTime consumption

NoNoYesMemory effects

NoneNoneSevereMatrix effects

Some pure element foilsOne internal standardSeveral external and internal standards

Calibration

Quantification

NoNoYesIsotope detection

FewFewSeveralSpectral interferences

Z < 9; Tl, Pb, BiZ < 13H, C, N, O, F, P, SElement limitations

Very goodVery goodExcellentDetection limits

Detection

NoNoYesConsumption

NoneNone1:100Diluition of acids

Any< 1%< 0.4%Dissolvation portion

NoneDigestion or suspensionDigestion or suspensionPreparation of solid

10-200 mg5-50 µL2-5 mLVolume or mass

Samples

INAATXRFICP-MSAnalytical Features

Comparison of Important Analytical Features of the Three Competitive Methods

Comparison of Important Analytical Features of the Three Competitive Methods

Benefits and Drawbacks of TXRF Applied to Element Analyses

Benefits and Drawbacks of TXRF Applied to Element Analyses

• Unique micro analytical capability• Unique micro analytical capability

• Great variety of samples and applications• Great variety of samples and applications

• Simultaneous multielementdetermination• Simultaneous multielementdetermination

• Low detection limits• Low detection limits

• Impossibility of totally non-destructive analysis• Impossibility of totally non-destructive analysis

• Limitation for non-volatile liquids• Limitation for non-volatile liquids

• Exception of low-Z elements• Exception of low-Z elements

• Limitation by high matrix contents• Limitation by high matrix contents

Benefits:Benefits: Drawbacks or limitations:Drawbacks or limitations:

• Simple quantification by internal standardization• Simple quantification by internal standardization

• No matrix or memory effects• No matrix or memory effects

• Wide dynamic range• Wide dynamic range

• Non-destructive surface and thin-layer analysis• Non-destructive surface and thin-layer analysis

• Simple automated operations• Simple automated operations

• Low running costs and maintenance• Low running costs and maintenance

• Restriction to flat or polished samples• Restriction to flat or polished samples

ReferencesReferences

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 SpectroscopyTXRF Special Issues – TXRF conference proceedings

Vol. 44, Issue 5 (1989) Vol. 46, Issue 10 (1991) Vol. 48, Issue 2 (1993)Vol. 52, Issue 7 (1997)Vol. 54, Issue 10 (1999)Vol. 56, Issue 11 (2001)Vol. 58, Issue 12 (2003)

ReferencesReferences

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

Handbook of X-Ray SpectrometryRene E. Van GriekenAndrzej A. Markowicz

ISBN: 0824706005Publisher: Marcel Dekker

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