Helium Replacement in Italy – HeRe in Italy 2-3 dicembre 2013 ENEA – C.R. Frascati

1. HeliumReplacement in Italy – HeRe in Italy 2-3 dicembre 2013 ENEA – C.R. Frascati Chemical characterization of thin films: focus on ICP-MS and Laser Ablation techniques Giovanna Zappa Responsabile del Coordinamento Qualità dei Test Chimici e Biologici ENEA-UTAGRI

2. AnalyticalTechniquesforElemental Analysis IonicCrhromatography AtomicSpectroscopy Electrochemistry • Ion selective electrodes • Polarography • Atomic Absorption • Flame • Furnace • ICP-OES • ICP-MS • Ion selective electrodes • Polarography X-RayFluorescence (XRF) • Wavelength dispersive XRF • Energy dispersive XRF NeutronActivationAnalysis (INAA) PhotoelectronSpectroscopy Mass Spectroscopy • X-Ray Photoelectron Spectroscopy (XPS) • Ultraviolet Photoelectron Spectroscopy (UPS) Proton-Induced γ-Ray Emission (PIGE) Particle-Induced X-Ray Emission (PIXE)

3. Spectroscopy Source: D.C. Harris, Quantitative Chemical Analysis, 7th Ed., Freeman, NY, 2007.

4. X-raySpectroscopy

5. X-rayFluorescence 3 1 1. An X-ray quantum hits an inner shell electron in a (sample) atom. The electron isremovedleaving the atom in an excited state. 2. The missinginnershell electron is replaced by an electron from an outershell. 3. The energydifferencebetween the inner and outershellisbalanced by the emission of a photon quantum (fluorescenceradiation). 2

6. X-RayFluorescence (XRF) AdaptedfromInnov-Xhandout for handheld XRF analyzers Note similar reference tables available from other XRF vendors

7. X-RayFluorescence (XRF): interferences and errorsources • Elements in the sample may produce 2 or more lines • Ka, Kb , La, Lb • Lg, La1, Lb1, Lb2 (can also have a1 and a2 lines, b1 and b2 lines, g lines, etc.) • Peak overlaps arising from the presence of multiple elements in the sample • Limited detector resolution • PeaksfromX-Ray source • Bremsstrahlung (more prominent in less dense samples) • Rayleigh peaks from X-ray source target (typically Ag La, Lb) • Compton peaks from X-ray source target (typically at energies < Ag La, Lb) • Sum peaks (two X-ray photons arriving at the detector at the same time) • E = Ka + Ka • E = Ka + Kb • Escape peaks (Si in the detector absorbing some of the energy from a X-ray) • E = Ka – Ka for Si (where Si line energy = 1.74 keV) • E = La – Kafor Si • Otherartifactpeaks • Product packaging, XRF cup, Mylar film, (measure what you want to measure) • Contaminants on XRF window or trace levels of elements in XRF window or detector

8. Common XRF Vs TXRF Common XRF spectrometry (EDXRF and WDXRF TXRF

9. Common XRF Vs TXRF common XRF spectrometry (EDXRF and WDXRF TXRF ■Solids (cut, polished and put intosuitableshape) ■Powders (aspressedpellets, fusedbeads or loosepowders in liquidcups) ■Liquids (in liquidcups) Powders directpreparation or as a suspension Liquids directpreparation sample amount: Lowμg / μlrange Always as a thin film, micro fragment or suspension of a powder Necessary sample amount: 1 - 10 g

10. TXRF: detectionlimits

11. Detectionlimits

12. AtomicSpectroscopy (UV-VIS) AFS AAS AES • Flame • Electrothermal Atomizer (graphitefurnace) • Flame • ICP Liquid Samples

13. M+ M+ + M x 100% Inductively Coupled Plasma (ICP) Processes in the plasma • Sample in the centre channel is heated • radiation and conduction • Sample is volatized, atomized, ionized • mainly singly charged ions (positive) produced Ionization occurs when the energy is high enough to cause an atom to lose one or more electrons (electron is moved to infinity) Extent of Element Ionization in Argon Plasma Calculated values of degree of ionization of M+ and M+2 (T = 7500K, ne = 1e15cm-3 ) *Houk 1986

14. ICP-AES Vs ICP-MS

15. Sample introduction system, torch and gas flows Nebulizers for sample introduction Typical sample introduction system: • Pneumatic • Concentric (excellent sensitivity and stability) • Cross Flow (can tolerate heavier matrix) • Direct Injection (very low flow, high sensitivity) • Ultrasonic Nebulizer Effect of nebulizer flow on plasma Plasma Flow: forms the plasma Auxiliary Flow: prevents torch melting, holds plasma away from injector tube Nebulizer Flow: carries sample, punches cooler channel through centre of plasma Sheath Gas Flow (not shown): added to the sample aerosol - allowing control of the velocity of the aerosol or diluting the sample aerosol The nebulizer gas punches a pathway through the plasma, allowing sample to be desolvated, volatilized, atomized and ionized

16. Comparisonamong ICP-MS, ICP-AES and AA Ex. oftypicalinstrumental Detection Limits (µg/l)

17. ICP-MS instrumentation sample Vacuum Ion source Mass analyzer Detector data processing 6 basic components of ICP-MS instruments: • Sample Introduction • Plasma Generation • Plasma-Mass Spectrometer Interface • Ion Optics • Mass Analyser (including Detector) • Vacuum System

18. Interferences in ICP-MS Spectroscopic interferences • Isobaric interferences: overlap of different isotopes with same mass/charge (e.g. 82Kr+ on 82Se+) • Oxides: appears at mass +16 amu e.g. 40Ar16O+ on 56Fe+) • Doubly charged ions: appears at half mass (e.g. 138Ba++ on mass/charge=69, i.e. 69Ga+) • Polyatomic interferences: molecular ion with same mass/charge, often formed between Argon and major elements in the sample matrix (e.g. 40Ar35Cl+ on 75As+) Physical interferences Mostly in the sample introduction area • Nebulizer aspiration variations (viscosity, surface tension) • Cone blockage • Memory effects • Typically observed in samples with high TDS • Ion signals vary on the basis of the sample • Can cause suppression or enhancement • Effect can be mass or time dependent • Space charge • Plasma ionization effects • Can be corrected by using internal standards • Preconditioning the interface can reduce effects

19. Isotone (± P) Original Nucleus P Isotope (± N) N Isobar (=Mass) Element Mass and Isotopes in ICP-MS • Mass (amu) • Total number ofprotons(P) andneutrons(N) in nucleus/atom • Isotone • Nuclide with the same N, but different P (or Mass) • Isotope • Nuclide with the same P, but different N (or Mass) • Isobar • Nuclide with the same Mass, but different P and N

20. Ca 40 96.941% K 39 93.258% Ca 41 ~ % K 40 0.012% Ca 42 0.647% K 41 6.730% Ar 38 0.063% Ar 39 ~ % Ar 40 99.60% Example of K isotopes, isobars and Isotone • Three K Isotopes • 39K, 40K, 41K (P=19) • Two Isobars for 40K • 40Ca (P=20, N=20) • 40Ar(P=18, N=22) • Two Isotone for 39K • 40Ca (P=20, N=20) • 38Ar (P=18, N=20)

21. POLYATOMIC Interferences in ICP-MS (MR: R = 4 000, HR: R = 10 000)

22. Reduction of Interferences • Sample Introduction System • Chilled spray chamber and lower sample uptake • Reduced vapour loading • Reduces oxygen availability • High power helps to fragment polyatomic • Cool Plasma • Reduced plasma temperature reduces ionization of argon containing species • Correction Equations (software) • Reliable for elemental isotope corrections • Variable success for polyatomic corrections • Interference Management Technique (IMT)Collision/Reaction Cell

23. ATMOSPHERE 760 Torr INTERFACE 1~5 Torr ION OPTICS ~ 1x 10-4 Torr PLASMA Skimmer Cone Sampler Cone Turbo-Molecular Pump Rotary Vacuum Pump Plasma and Ion Sampling Interface • Ion sampling via interface cones • Sampler cone (~1.0mm orifice) • Skimmer cone (~0.5mm orifice)

24. L4 L3 L2 L1 Extraction lens Skimmer Cone Mass Analyzer Photon Stop Ion Optics / Lens System • Designed to provide for the efficient transfer of ions from the skimmer to the entrance of mass analyzer • Remove photons and neutrals • Focus ions into quadrupole/mass analyzer

25. Torch Ion Optics Detector Quadrupole Turbo Pump Turbo Pump Interface Rotary Pump Rotary Pump Vacuum System • Required to allow transmission of ions without collisions • Vastly different operating pressures of the plasma and mass spectrometer affect the design. • A differentially pumped vacuum system is the most economical means of handling high gas loads. • Three chamber systems are most common

26. Typical Collision/Reaction Cell in ICP-MS pressurized multipole (quadrupole, hexapole or octapole) in front of the mass analyzer • - Various reaction gasses used depending on application (H2,He, NH3, CH4, etc) • Interfering species are attenuated by converting them to non-interfering species.

27. Bruker CRI PE DRC Thermo CCT Interference Management Techniques Dynamic Reaction Cell (DRC) Collision Reaction Interface (CRI) Agilent ORS • Collision Cells (CC or CCT, used by Agilent and Thermo)

28. Collision/Reaction Cell For collision cells, ion-molecule collisional fragmentation and energy discrimination are dominant mechanisms for interference reduction simple gasses must be used - e.g. He or H2 For reaction cells, ion-molecule chemical reaction is the dominant mechanism for interference reduction highly reactive gasses can be used - e.g. NH3 or CH4

29. Direct analysis of solidsamples by MS To generate analyte ions, 2 principles : simultaneous evaporation/atomization and ionization processes within one step (SIMS) ‘‘post-ionization’’ - evaporation/atomization processes aseparated in time and space from the ionization step (SNMS, GDMS, LA-ICP-MS) possibility to optimize the sampling and ionizationprocesses separately Matrix independence better suitability for non-matrix matched calibration approaches

30. Direct analysis of solidsamples • Need to calibrate with solid samples of known composition • The lack of appropriate Certified Reference Materials can restrict applications to quantitative analysis calibrationstrategies: • preparationof in-housecalibrationsamplesusingdopedpressedpowders, • fusion of powderedreferencematerialsintoglass, • directionimplantation of a known dose of the elementof interestinto a matrix-matchedsubstrate, • use of isotope dilution mass spectrometry (ID-MS), • non-matrixmatchedcalibrationapproaches(solid–solid and liquid–solid)

31. Certified Reference Materials (CRM) Fit for purposeCRM: chemicalcomposition (matrix), concentration of the elements homogeneity of the elements in the solidsample roughnessof the sample surface

32. Laser Ablation- ICP MS A short-pulsed, high power laser beamisfocused or imagedonto the sample surface in an inert gas atmosphereunder normalpressure, within an airtightablationcell. The interactionbetweenthe laser beam and the sample leads to an aerosol formationof the solid. A carrier gas flushesthrough the ablationcelland transports the particle-containing aerosol into the ICPMS, whereitisvaporized, atomized, and ionized. General capabilities. LA-ICP-MS allows trace and ultra trace elementanalysisat high lateral and depthresolution (few mm and hundredsof nm, respectively) A wide variety of samplessuchasconducting, non-conducting, hard, soft, and coatedsolidscan be directlyanalyzed. The samplesmust be kept in a stableform (e.g. solidorpressedpowder and dry or cooled–frozen)

33. Laser types and wavelenghts

34. Laser ablation fspulse ns pulse

35. Laser Ablation- ICP MS Oneof the mainlimitationsof LA-ICP-MS, and basically of all laser-basedsamplingtechniques, is the occurrence of non-stoichiometriceffectsin the transientsignals, definedaselementalfractionation. Allprocessesinvolved in LA-ICP-MS (the aerosol formationprocess, the transport of the aerosol into the ICP, and the conversionof the aerosol intoionswithin the ICP) maypotentiallyalter the stoichiometriccomposition of the laser-generatedaerosol dependingon the chemical and physicalproperties of the elements, resultingin unknowncontributions to elementalor isotopicfractionationeffects.

36. Laser InducedBreakdownSpectroscopy (LIBS)

37. Ionizationof atomic and molecular speciesin Laser-Induced BreakdownSpectroscopy MultiphotonIonization (MPI) Inverse Bremsstrahlung (IB) Atoms or molecules undergo simultaneous absorption of sufficient numbers of photons to cause ionization (or the ejection of electrons from the valence to the conduction band, in the case of metals) Electronsacquire energy from the absorbance of photons and collisions with atoms, ions, and molecules If the energyof the free electron is greater than the ionization potential of a neutral species, it can ionize a molecule (M) by colliding with it. This produces two lower-energy free electrons, which can gain more energy from the electric field, causing ionization of other neutrals and two more electrons

38. LA-ICP-MS, µXRF and LIBS comparison

39. Samplingand sample pre-treatment (representativeness) Development of the analyticalmethods (analysis of liquidsamples) Select the appropriate laser source Evaluatevaporization rate on realsamples Select the appropriate CertifiedRefenceMaterials Evaluateprecision and accuracy EvaluateUncertaintysources and calculateMeasurementUncertainty Comparisonbetweentwo or more analyticaltechniques Development of methodsbased on LA-ICP-MS

40. Thankyou for yourattention