Trace Element Analysis: Time and Cost Savings with TXRF. Bruker AXS Microanalysis GmbH Berlin, Germany

Transcription

1 Trace Element Analysis: Time and Cost Savings with TXRF Bruker AXS Microanalysis GmbH Berlin, Germany

2 Welcome Today s Topics Introduction to XRF and TXRF The S2 PICOFOX benchtop TXRF system Application studies - Liquid samples - urine - Suspensions - blood - Solid samples - NaCl (pharma) - Micro particles - nano particles Method comparison & summary Interactive Q & A Your Host Arkady Buman Business Development Mgr Madison, WI, USA Speakers Dr. Hagen Stosnach Applications Scientist TXRF Berlin, Germany Dr. Armin Gross Global Product Manager TXRF Berlin, Germany 2

3 Introduction to XRF and TXRF Armin Gross

4 Principles of X-ray fluorescence (XRF) spectroscopy 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 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) 4

5 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 5

6 Principles of X-ray fluorescence spectroscopy Common XRF optics X-ray tube Sample Detector Beam angle: 45 o / 45 o 6

7 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!!! 7

8 Principles of total reflection X-ray fluorescence (TXRF) spectroscopy Total reflection X-ray fluorescence spectroscopy Detector X-ray tube Sample carrier Beam angle: 0 o / 90 o 8

9 Principles of total reflection X-ray fluorescence spectroscopy Samples for total reflection X-ray fluorescence spectroscopy: Powders: Liquids: Direct preparation or as suspension Direct preparation always as a thin film, micro fragment or suspension of a powder necessary sample amount: Low µg respectively µl range 9

10 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 10

11 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 kcps Automatic version - 25 sample cassette 11

12 S2 PICOFOX Element sensitivity The S2 PICOFOX detects elements from Na(11) to U(92) The element sensitivities depend on the atomic number The sensitivity factors are calibrated ex works Element sensitivity K-lines L-lines Atomic number 12

13 Audience poll 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 treatment Grinding Dissolving Dilution Extraction Digestion 13

14 Why Wait for Sample Prep! Ease of Use and Versatility of TXRF Analysis Hagen Stosnach

15 S2 PICOFOX Application overview Focus on medical and pharmaceutical applications Sample type Liquids Suspensions Solids, powders Particles Application urine analysis whole blood and blood serum testing raw materials in pharmaceutical production, e.g. NaCl nano particles 15

16 Sample preparation Liquid samples You ll need just a few steps for the preparation of liquid samples fill sample in micro tube add internal standard homogenize pipette on carrier 16

17 Sample preparation Final steps dry by heat / vacuum load the instrument start data aquisition 17

18 Liquid samples Urine Introduction The trace element content of urine is an indicator for the human health status Task Participation in round robin test for urine samples Sample preparation and measurement Direct application after addition of a Ga standard Measurement time 1000 s After treatment with HNO 3 directly on the carrier, samples were measured again 18

19 Liquid samples Urine Challenges of urine samples testing: Detection limits in the low ppb range required High amount of chlorine and calcium disturb TXRF measurements with sum peaks of matrix elements Solution Vaporize Cl with HNO 3 Perform second measurement of same sample TXRF spectrum of urine sample grey = before, blue = after HNO 3 treatment 19

20 Liquid samples Urine Results TXRF received certification for the elements As, Se, Zn Conclusion TXRF allows precise and accurate urine analysis after direct sample preparation Element TXRF (µg/l) Ref. (µg/l) LLD (µg/l) Sample A As Se Zn Sample B As Se Zn

21 Sample preparation Suspensions Suspensions can be analyzed just after dilution dilute sample with distilled water add internal standard homogenize pipette on carrier 21

22 Suspensions Blood analysis Introduction Analysis of nutrition-relevant elements (Cu, Fe, Zn, Se) Analysis of other e.g toxic elements and Pt (chemotherapy) Task Analysis 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 22

23 Suspensions Blood analysis Results I Serum reference standard (t = 600 s) good correlation for Cu, Zn & Se overestimation of Fe improved calibration curve required Note Confidence level of reference values is up to 35 % (!) Reference values (µg/l) TXRF values (µg/l) Se Cu Zn Fe 23

24 Suspensions Blood analysis Results II Whole blood reference standard (t = 600 s) application of optimized blood calibration excellent correlation for Fe, Cu, Zn, Se and others Reference values (µg/l) P S K Ca Rb Sr Pb Se Cu Zn Fe TXRF values (µg/l) 24

25 Suspensions Blood analysis Reproducibility Precise TXRF results although sample digestion was avoided 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, ,9 0,09 1,964 0,20 Cu µg/l 66 2,2 62 2, Zn µg/l 501 4, , Se µg/l 12 0, , ) : Sector-Field Inductively-Coupled Plasma Mass Spectroscopy 2) : Atomic Absorption Spectroscopy 25

26 Sample preparation Solid and powder samples I Solids are ground to fine particle size and resuspended for direct analysis without digestion fill powder in mortar grind carefully weigh about mg transfer to tube 26

27 Sample preparation Solid and powder samples II suspend in detergent solution add standard homogenize pipette on carrier 27

28 Solid samples Pharmaceuticals purity control Example: Raw material NaCl Analytical task analysis of impurities with regard to the limit value of 1 mg/kg for As in pure NaCl Samples NaCl (p.a. grade), Carl Roth GmbH - As: < 0.4 mg/kg same sample, spiked with As Preparation Dissolution of some mg in 1 ml water Resuspension of about 50 mg in 1.5 ml detergent (Triton X-100) 28

29 Solid samples Pharmaceuticals purity control Recovery results Trace element concentrations of Ca, Ti, Cr, Fe, Ni, Cu, Zn and Br were determined simultaneously Measured values As (mg/kg) 5,0 4,0 3,0 2,0 1,0 y = 1,1157x + 0,0986 R 2 = 0,9972 0,0 0,0 1,0 2,0 3,0 4,0 5,0 Spiked As (mg/kg) 29

30 Solid samples Pharmaceuticals purity control 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 30

31 Sample preparation Microparticles Microparticles are measured semi-quantitatively and non-destructively dab vacuum grease on carrier pick-up some particles with a (glass) rod drop particles on grease 31

32 Particles Characterization of nanoparticles Analytical question element ratios in CdSe nanoparticles coated with ZnS Analytical issues extremely small sample amount (R&D) non-destructive method preferred TXRF measurement transfer of nanoparticles to quartz carrier by cotton bud standardless quantification Results even smallest sample amounts allow the determination of element ratios in nanoparticles 32

33 Particles Characterization of nanoparticles Results Element ratios of nanoparticles even smallest sample amounts allow the determination of element ratios in nanoparticles S2 PICOFOX Standardless analysis applied Ratio (wt.-%) Sample 1 Sample 2 Sample 3 0 Zn/S Cd/Se Zn/Cd Measured ratios of 3 samples versus target value ( ) 33

34 Summary and Method Comparison Armin Gross

35 Summary biological matrices Wait Wait for Sample Prep! TXRF can be easily applied to all biological matrices Sample digestion is hardly required Biological matrix Typ. volume Blood - whole blood 500 µl Blood - serum, small volumes < 10 µl Urine ml Sample preparation for TXRF 1 : 1 dilution with H 2 O, addition of internal Ga standard 1 :2 dilution with H 2 O, pipetting on carrier addition of 1 µl Ga standard solution direct addition of internal standard, fume off Chlorine by HNO 3 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 35

36 Summary biological matrices Low levels of detection Detection limits are in the low to middle ppb range 1000 Detection Limits in Biological Matrices urine whole blood blood serum 100 (µg/l) 10 1 Ca V Cr Mn Fe Co Ni Cu Zn As Se Br Rb Sr Hg Pb 36

37 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 Element Concentration (ppm) Excitation mode 3s 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 37

38 TXRF versus AAS & ICP Time-to-result Solid samples and suspensions Shorter time needed from sampling to the final quantitative result TXRF ICP AAS 38

39 TXRF versus AAS & ICP Productivity Factory calibrations one time Immediate results for unknown matrices standardless Shorter 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 39

40 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 chemicals Expensive maintenance contracts TXRF ICP-MS ICP-OES AAS 40

41 Comparison TXRF versus AAS & ICP-OES 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 41

42 Any Questions? Please type in questions you may have for any of our speakers in the Question form and then click Submit.

43 Thank you for attending! Please take a moment to complete the brief survey on your screen. Your feedback is very important to us. Copies of this presentation and related TXRF resource materials will be ed to you.

44 Meet us at: IFPAC/PAT: International Forum for Process Analytical Chemistry & Technology Jan 26-28, Baltimore, MD SME & CME: Society for Mining, Metallurgy and Exploration & National Western Mining Conference Feb 23-25, Denver, CO PITTCON: Mar 8-13, Chicago, IL Frontiers in XRF Seminar Northwest: Your free 1-day seminar on the theory, instrumentation, preparation and application of ED and WDXRF Apr 25, Seattle, WA ISWM: International Symposium on Metallomics Jun 7-10, Cincinnati, OH Denver X-ray Conference: Jul 27-31, Colorado Springs, CO 44