trace element analysis: time and cost savings with txrf · trace element analysis: time and cost...
TRANSCRIPT
Trace Element Analysis: Time and Cost Savings
with TXRF
Bruker AXS Microanalysis GmbH Berlin, Germany
23.01.20092
Welcome
Today’s TopicsIntroduction to XRF and TXRFThe S2 PICOFOX benchtop TXRF systemApplication studies
- Liquid samples - urine- Suspensions - blood- Solid samples - NaCl (pharma)- Micro particles - nano particles
Method comparison & summaryInteractive Q & A
Speakers
Dr. Hagen Stosnach Applications Scientist TXRF Berlin, Germany
Dr. Armin Gross Global Product Manager TXRF Berlin, Germany
Your HostArkady Buman Business Development Mgr Madison, WI, USA
Introduction to XRF and TXRF
Armin Gross
23.01.20094
Principles of X-ray fluorescence (XRF) spectroscopy
1
2
3 3
2
11. An X-ray quantum hits an inner
shell electron in a (sample) atom. The electron is removed leaving the atom in an excited state
2. The missing inner shell electron is replaced by an electron from an outer shell
3. The energy difference between the inner and outer shell is balanced by the emission of a photon (fluorescence radiation)
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Principles of X-ray fluorescence spectroscopy
The energy, and therefore the wavelength, of the X-ray fluorescence radiation is characteristic for the different chemical elements.
QUALITATIVE ANALYSIS
The intensity of the X-ray fluorescence radiation is, in first approximation, proportional to the element concentration.
QUANTITATIVE ANALYSIS
Low Z High Z
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Principles of X-ray fluorescence spectroscopy
“Common” XRF optics
Beam angle: 45o / 45o
X-ray tube
Sample
Detector
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Principles of X-ray fluorescence spectroscopy
Samples for common XRF spectrometry (ED and WD XRF):
Solids (cut, polished and made into suitable shape)Powders (as pressed pellets, fused beads or loose powders in liquid cups)Liquids (in liquid cups)
Necessary sample amount: from 1 g to 10 g !!!
23.01.20098
Principles of total reflection X-ray fluorescence (TXRF) spectroscopy
Total reflection X-ray fluorescence spectroscopy
Beam angle: 0o / 90o
X-ray tube
Detector
Sample carrier
23.01.20099
Principles of total reflection X-ray fluorescence spectroscopy
Samples for total reflection X-ray fluorescence spectroscopy:
Powders: Direct preparation or as suspensionLiquids: Direct preparation
always as a thin film, micro fragment or suspension of a powder
necessary sample amount: Low µg respectively µl range
23.01.200910
Principles of total reflection X-ray fluorescence spectroscopy
Quantification in total reflection X-ray fluorescence spectroscopy
In TXRF the samples are prepared as thin films or layers
Therefore matrix effects are negligible
QUANTIFICATION IS POSSIBLE THROUGH:
Sensitivity of the instrument for element lines (energy-dependent)
Net intensity of element lines
Known concentration of an internal standard element
Negligible absorption of primary beam and fluorescence radiation
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The instrument S2 PICOFOX
Benchtop TXRF spectrometer “S2 PICOFOX”
Metal-ceramic X-ray tube- Mo anode- air-cooled- optionally other tubes available
Multilayer monochromator
XFlash© Silicon Drift Detector- electro-thermally cooled- ≤149 eV @ 100 kcps
Automatic version- 25 sample cassette
23.01.200912
S2 PICOFOX Element sensitivity
The S2 PICOFOX detects elements from Na(11) to U(92)The element sensitivities depend on the atomic numberThe sensitivity factors are calibrated ex works
Element sensitivity
L-linesK-lines
Atomic number
23.01.200913
Please use your mouse to answer the question on your screen:
How do you currently treat your samples before analysis? Check all that apply:
No treatmentGrindingDissolvingDilutionExtractionDigestion
Audience poll
Why Wait for Sample Prep!
Ease of Use and Versatility of TXRF Analysis
Hagen Stosnach
23.01.200915
S2 PICOFOX Application overview
Focus on medical and pharmaceutical applications
Sample type Application
Liquids urine analysis
Suspensions whole blood and blood serum testing
Solids, powders raw materials in pharmaceuticalproduction, e.g. NaCl
Particles nano particles
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Sample preparation Liquid samples
fill sample in micro tube
add internal standard
homogenize
pipette on carrier
You‘ll need just a few steps for the preparation of liquid samples
23.01.200917
Sample preparation Final steps
dry by heat / vacuum
load the instrument
start data aquisition
23.01.200918
Liquid samples Urine
IntroductionThe trace element content of urine is anindicator for the human health status
TaskParticipation in round robin test for urine samples
Sample preparation and measurementDirect application after addition of a Ga standardMeasurement time 1000 sAfter treatment with HNO3 directly on the carrier, samples were measured again
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Liquid samples Urine
TXRF spectrum of urine samplegrey = before, blue = after HNO3 treatment
Challenges of urine samples testing:
Detection limits in the low ppb range requiredHigh amount of chlorine and calcium disturb TXRF measurements with sum peaks of matrix elements
SolutionVaporize Cl with HNO3
Perform second measurement of same sample
23.01.200920
Liquid samples Urine
Element TXRF (µg/l) Ref. (µg/l) LLD (µg/l)
Sample A
As 116 95 1.5
Se 9.5 12 1.5
Zn 281 253 2.0
Sample B
As 228 206 1.3
Se 26.7 28.5 1.3
Zn 871 788 1.7
ResultsTXRF received certification for the elements As, Se, Zn
ConclusionTXRF allows precise and accurate urine analysis after direct sample preparation
23.01.200921
Sample preparation Suspensions
dilute sample with distilled water
add internal standard
homogenize
pipette on carrier
Suspensions can be analyzed just after dilution
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Suspensions Blood analysis
IntroductionAnalysis of nutrition-relevant elements (Cu, Fe, Zn, Se)Analysis of other e.g toxic elements and Pt (chemotherapy)
TaskAnalysis of whole blood and blood serum standards
Sample preparation
Serum- 1:10 dilution with water (p.a. grade)- Addition of Ga for internal standardization
Whole blood- 1:1 dilution with water (p.a. grade)- Addition of Ga for internal standardization
23.01.200923
Suspensions Blood analysis
Results ISerum reference standard (t = 600 s)
good correlation for Cu, Zn & Seoverestimation of Feimproved calibration curve required
Note Confidence level of reference values is up to 35 % (!)
10
100
1000
10000
10 100 1000 10000
TXRF values (µg/l)
Ref
eren
ce v
alue
s (µ
g/l)
SeCuZnFe
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Suspensions Blood analysis
Results IIWhole blood reference standard (t = 600 s)
application of optimized “blood calibration”excellent correlation for Fe, Cu, Zn, Se and others
10
100
1000
10000
100000
1000000
10000000
10 100 1000 10000 100000 1000000 10000000
TXRF values (µg/l)
Ref
eren
ce v
alue
s (µ
g/l) P
SKCaRbSrPbSeCuZnFe
23.01.200925
Suspensions Blood analysis
ReproducibilityPrecise TXRF results although sample digestion was avoided
1): Sector-Field Inductively-Coupled Plasma Mass Spectroscopy2): Atomic Absorption Spectroscopy
Serum (ClinCheck L2) Whole blood (Seronorm L2)
Element Unit TXRF Std. dev. Reference 1) Std. dev. TXRF Std. dev. Reference 2) Std. dev.
Fe mg/l 440 7,4 435 12 2,9 0,09 1,964 0,20
Cu µg/l 66 2,2 62 2,1 1685 43 1562 312
Zn µg/l 501 4,9 504 6,9 2194 118 2225 334
Se µg/l 12 0,29 12 1,0 97 18 102 26
23.01.200926
Sample preparation Solid and powder samples I
fill powder in mortar
grind carefully
weigh about 20-50 mg
transfer to tube
Solids are ground to fine particle size and resuspended for direct analysis without digestion
23.01.200927
Sample preparation Solid and powder samples II
suspend in detergent solution
add standard
homogenize
pipette on carrier
23.01.200928
Example: Raw material NaCl
Analytical taskanalysis of impuritieswith regard to the limit value of 1 mg/kg for As in pure NaCl
SamplesNaCl (p.a. grade), Carl Roth GmbH- As: < 0.4 mg/kg
same sample, spiked with As
PreparationDissolution of some mg in 1 ml waterResuspension of about 50 mg in 1.5 ml detergent (Triton X-100)
Solid samples Pharmaceuticals – purity control
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Recovery resultsy = 1,1157x + 0,0986
R2 = 0,9972
0,0
1,0
2,0
3,0
4,0
5,0
0,0 1,0 2,0 3,0 4,0 5,0
Spiked As (mg/kg)
Mea
sure
d va
lues
As
(mg/
kg)Trace element
concentrations of Ca, Ti, Cr, Fe, Ni, Cu, Zn and Br were determined simultaneously
Solid samples Pharmaceuticals – purity control
23.01.200930
Detection limits
(600 s)
Conc. LLD
(mg/kg)Ca 2,4 0,57
Ti 1,8 0,25
Cr 0,85 0,17
Fe 11 0,13
Ni 0,29 0,09
Cu 0,34 0,08
Zn 0,33 0,07
As 1,2 0,07
Se (i.s.) 20 0,07
Br 19 0,08
Solid samples Pharmaceuticals – purity control
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Sample preparation Microparticles
dab vacuum grease on carrier
pick-up some particles with a (glass) rod
drop particles on grease
Microparticles are measured semi-quantitatively and non-destructively
23.01.200932
Particles Characterization of nanoparticles
Analytical questionelement ratios in CdSe nanoparticlescoated with ZnS
Analytical issuesextremely small sample amount (R&D)non-destructive method preferred
TXRF measurementtransfer of nanoparticles to quartz carrier by cotton budstandardless quantification
Resultseven smallest sample amounts allow the determination of element ratios in nanoparticles
23.01.200933
Results
even smallest sample amounts allow the determination of element ratios in nanoparticles
S2 PICOFOX“Standardless”analysis applied
Particles Characterization of nanoparticles
Element ratios of nanoparticles
Sample 2Sample 1
Sample 3
10
1
4
0
2
4
6
8
10
12
Zn/S Cd/Se Zn/Cd
Rat
io (w
t.-%
)
Measured ratios of 3 samples versus target value ( )
Summary and Method Comparison
Armin Gross
23.01.200935
Summary biological matrices Wait Wait for Sample Prep!
TXRF can be easily applied to all biological matricesSample digestion is hardly required
Biological matrixTyp. volume
Sample preparation for TXRF
Blood - whole blood 500 µl1 : 1 dilution with H2 O, addition of internal Ga standard
Blood - serum, small volumes < 10 µl1 :2 dilution with H2 O, pipetting on carrier addition of 1 µl Ga standard solution
Urine mldirect addition of internal standard, fume off Chlorine by HNO3
Tissue homogenates µl 1 : 1 dilution with Y standard solution
Seminal fluid µl direct addition of internal standard
Cerebrospinal fluid µl direct addition of internal standard
Mother’s milk ml direct addition of internal standard
Tear fluid µl to ml direct addition of internal standard
23.01.200936
Summary biological matrices Low levels of detection
Detection limits are in the low to middle ppb range
Detection Limits in Biological Matrices
1
10
100
1000
Ca V Cr Mn Fe Co Ni Cu Zn As Se Br Rb Sr Hg Pb
(µg/
l)
urinewhole bloodblood serum
23.01.200937
Summary pharmaceuticals TXRF meets Pharmacopeia
Metals with significant safety concern (EMEA): TXRF with Mo excitation fulfills required LLDs
Method development for W excitation not yet finished
ElementConcentration
(ppm)Excitation
mode3s LLD (ppm)
Pt 1 Mo 0,06
Pd 1 W
Ir 1* Mo 0,06
Rh 1* W
Ru 1* W
Os 1* (volatile, not analyzable)
Mo 2,5 W
Ni 2,5 Mo 0,08
Cr 2,5 Mo 0,19
V 2,5 Mo 0,24
*) subclass limit for total amount of Ir, Rh, Ru, Os
23.01.200938
TXRF versus AAS & ICP Time-to-result
Solid samples and suspensions
Shorter time needed from sampling to the final quantitative result
AAS
ICP
TXRF
23.01.200939
TXRF versus AAS & ICP Productivity
Factory calibrations – one timeImmediate results for unknown matrices – standardlessShorter learning curve – lab standardization
ICP calibration about 30% of daily worktime
AAS calibration about 15% of daily worktime
TXRF automatic gain calibration about 2 % of daily worktime
23.01.200940
TXRF versus AAS & ICP Cost of ownership
Use of expensive accessories (AAS: graphite tubes) Need for consumables (noble gases, standards) Complicated sample preparation equipment and hazardous chemicalsExpensive maintenance contracts
AAS
ICP-OES
ICP-MS
TXRF
23.01.200941
The S2 PICOFOX can be an alternative to AAS and/or a
complement for existing ICP-OES systems
Major benefits of the S2 PICOFOX
fast and simple sample preparation
flexibility with regard to sample types
easy multi-element analysis without external calibration
low maintenance and operating costs
Comparison TXRF versus AAS & ICP-OES
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23.01.200944www.bruker-axs.com
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