Laser Ablation ICP-MS

Transcription

1 LASER ABLATION 1

2 Laser Ablation ICP-MS CETAC LSX Thermo Finnigan Element 2

3 Gold can be melted and recast and is therefore virtually untraceable 3

4 DISTINGUISH GOLD SAMPLES BASED ON TRACE ELEMENTS? 4 Watling et al., Spectrochim. Acta Part B 1994, 49B,

5 DEVELOPMENTS IN LASER ABLATION GÜNTHER et al., ANAL. CHEM. 2003, 75, 341A; TrAC 2005, 24, 255. UV LASERS (266, 213, 193 nm) HOMOGENIZED BEAM PROFILE HELIUM TRANSPORT GAS FRACTIONATION 1. VARIATION OF SIGNAL RATIO vs TIME AS DIG SINGLE PIT 11.MEAS. SIGNAL RATIOS DIFFER FROM THOSE IN SAMPLE SOLUTIONS: FLAT BOTTOM CRATERS VERTICAL SIDES SHORT PULSE (fs) LASER (RUSSO et al., ANAL. CHEM. 2002, 74, 70A). 5

6 PARTICLE SIZE EFFECTS IN LASER ABLATION GÜNTHER & GUILLONG JAAS 2002, 17, 831 AESCHLIMAN et al. JAAS 2003, 18,

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8 Particles from Ablated Y2O3 Pellet Track length velocity ~ 27 m/s 8

9 Pressed pellet Fernald soil blank 9

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12 SINGLE SPOT ABLATION 12

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14 FEMTOSECOND LASER ABLATION RUSSO et al. JAAS 2002, 17, ANAL. CHEM. 2003, 75, , 76,

15 Femtosecond Laser Ablation Nanosecond laser ablation is partly a thermal process Differences in the vaporization properties of elements leads to elemental fractionation With femtosecond pulses, the ablation process occurs by a mechanism far less dependent on thermal effects. Melting is not observed with pulse widths < 1 ps. 15

16 Crater Profiles Crater profiles for 100 fs and 4 ns lasers after 50 pulses 16

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18 UV fs LASER ABLATION INGO HORN UNIV. HANNOVER 18

19 fs-laser ablation system Optics Laser Stretcher/ Compressor Regenerative Amplifier M1 ω Seed laser M5 ½WP1 3ω M4 M12 M6 TP M2 Pump laser 196 nm 785 nm THG SHG ½WP2 M3 ω 2ω ½WP3 ω 3ω M9 M8 FHG ω 3ω+4ω 4ω M7 ω 3ω 2ω 100fs= sec. By comparison, if traveling at the speed of light for 100 fs you would only just cover about 30 μm in distance. MC-ICP-MS or ICP-OES Gas 19 Sample cell

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22 CALIBRATE LASER ABLATION? COMPENSATE FOR MATRIX DEPENDENCE OF ABLATION PROCESS MATCHED STANDARDS MEAS. ANALYTE REL. TO MINOR ISOTOPE OF ELEMENT AT KNOWN CONCENTRATION CALIBRATE REL. TO SOLUTION AEROSOL? BECKER JAAS 2001, 16, 602 AESCHLIMAN JAAS 2003, 18,

23 CETAC LASER ABLATION SYSTEM camera TSI PIEZOBALANCE zoom lens pump 20% Nd:YAG laser (266 nm) impactor argon inlet translation stage argon inlet 80% electrostatic precipitator ESI NEBULIZER FINNIGAN ICP-MS ESA magnet calibration solution 10% 90% waste ICP 23

24 4.0 NIST STEEL -1 Signal (counts s ) / Ablated solid Cr + V Solution Ni Time (s) 24

25 Calibration of LA-ICP-MS with Dried Solution Aerosols Simultaneous introduction of particles from a LA cell and desolvated aerosol particles from a micro-flow nebulizer Stotal = Ssolid + Ssolution = RX,solid TLAt[X]solid + RX,soln VTneb[X]soln RX TLA t [X]solid V Tneb [X]soln isotope-specific response factor (signal/ng X) transport from LA cell (ng solid/s) time of ablation transient (s) concentration of isotope in solid (ng X/ng solid) volume of solution injected to ICP (L) nebulizer efficiency isotopic concentration in solution standard (ng X/L) 25

26 NIST 612 Glass (13 Elements, 5 Replicates) Particle transport from the LA cell was measured using a piezoelectric microbalance Each replicate was generated by firing 50 laser shots per localized spot on the sample A two-point calibration plot for each replicate was prepared and an average calculated All elements were measured in medium resolution (R = m/δm = 4000) CONCENTRATION (ppm) Mn Fe Co Ni Cu Ba Nd Sm Eu Dy Er Tl Pb (55Mn+) (56Fe+) (59Co+) (60Ni+) (63Cu+) (138Ba+) (146Nd+) (147Sm+) (151Eu+) (161Dy+) (166Er+) (205Tl+) (208Pb+) MEASURED CERTIFIED (39.6) 51 (35.5) 38.8 (37.7) (41) (36) (39) (36) (35) (39) (15.7) Relative Diff. (%)

27 NIST 1264a Steel (8 Elements) 266 nm QUAD. Nd:YAG LASER, CETAC LSX-100 AVG. 30 SPOTS, TWO-POINT STD. ADDNS. 50 SHOTS PER SPOT, MED. RES. PARTICLE TRANSPORT MEAS. WITH MICROBALANCE CONCENTRATION (wt %) V Cr Co Ni Cu W Pb Bi (51V+) (52Cr+) (59Co+) (60Ni+) (63Cu+) (184W+) (208Pb+) (209Bi+) MEAS CERT. (INFO) (0.0009)

28 NIST 1264a Steel (8 Elements) 193 nm ArF LASER AVG. 3 SPOTS, TWO-POINT STD. ADDNS. 50 SHOTS PER SPOT, MED. RES. PARTICLE TRANSPORT MEAS. WITH MICROBALANCE CONCENTRATION (wt %) V Cr Co Ni Cu W Pb Bi (51V+) (52Cr+) (59Co+) (60Ni+) (63Cu+) (184W+) (208Pb+) (209Bi+) MEAS CERT. (INFO) (0.0009)

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30 Multivariate Analysis in LA-ICP-MS 30

31 Laser Ablation of NIST 1224 Steel end laser ablation Signal (counts/s) Cu 53Cr Co 60Ni 59 Co Cr + Ni Cu + start laser ablation 98Mo 184W signal from argon blank Mo 184 W Time (s) 31

32 STEEL SAMPLES 32

33 Principal Component Analysis Eigenvector decomposition of covariance matrix Matlab toolbox developed by Eigenvector Research, Inc. Traditionally applied to IR spectra Used to extract reduced dimension factors that describe trends and similarities/dissimilarities in data from multi-component spectra 33

34 Comparison of Stainless Steel Washers from the Same Bag 4.0 (16 Elements) Q Residual % C.I % C.I Sample Number 34

35 Comparison of Two Stainless Steel Washers from the Same Box (19 elements) 12 99% C.I. 10 Q Residual Sample Number 35

36 Chemometric Comparison of Seven Carbon Steels (25 Isotope Model) Principal Component NIST NIST NIST 1263a 1 NIST 1264a_1 0 NIST 1264a_ pipe bar plate Principal Component 3 36

37 Comparison of SRM 139 and 139b to 139a (20 Elements) 12 SRM139b SRM Q Residual % C.I. 2 95% C.I Replicate 37

38 Q Residual Comparison of Two Strands from a Single Copper Wire (7 Elements) % C.I. 95% C.I Sample Number 38

39 Copper Wire Comparison 10 Wire 1 Wire 2 Wire 3 Wire 4 Wire 5 Wire 6 99% C.I. Q Residual E Model Wire 39