Transcript LASER ABLATION Laser Ablation ICP-MS CETAC LSX 500 www.cetac.com www.thermo.com Thermo Finnigan Element “Gold can be melted and recast and is therefore virtually untraceable”

LASER ABLATION
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Laser Ablation ICP-MS
CETAC LSX 500
www.cetac.com
www.thermo.com
Thermo Finnigan Element
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“Gold can be melted and recast
and is therefore virtually untraceable”
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DISTINGUISH GOLD SAMPLES BASED ON TRACE ELEMENTS?
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Watling et al., Spectrochim. Acta Part B 1994, 49B, 205-219.
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
2. 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).
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PARTICLE SIZE EFFECTS
IN LASER ABLATION
GÜNTHER & GUILLONG
JAAS 2002, 17, 831
AESCHLIMAN et al.
JAAS 2003, 18, 1008
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Particles from Ablated Y2O3 Pellet
Track length u
velocity ~ 27 m/s
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Pressed pellet
Fernald soil blank
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10
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SINGLE SPOT ABLATION
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FEMTOSECOND LASER ABLATION
RUSSO et al.
JAAS 2002, 17, 1072.
ANAL. CHEM. 2003, 75, 6184
2004, 76, 379.
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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.
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Crater Profiles
Crater profiles for 100 fs and 4 ns lasers after 50 pulses
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UV fs LASER ABLATION
INGO HORN
UNIV. HANNOVER
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fs-laser ablation system
Optics
Laser
Stretcher/
Compressor
Regenerative
Amplifier
M1
ω
M8
M5
½WP1
3ω
M4
M12
M6
TP
M2
Pump
laser
196 nm
785 nm
THG
SHG ½WP2
ω
2ω
M3
M9
ω
3ω
4ω
FHG
ω
3ω+4ω
M7
ω
3ω
2ω
½WP3
Seed
laser
100fs=0.0000000000001sec.
By comparison, if traveling
at the speed of light for
100 fs you would only
just cover about 30 mm in
distance.
MC-ICP-MS
or
ICP-OES
Gas
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Sample cell
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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, 872-877.
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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
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4.0
NIST STEEL
-1
Signal (counts s ) / 10
6
3.5
Ablated
solid
3.0
2.5
2.0
1.5
52
Cr+
51
V+
1.0
Solution
0.5
60
Ni+
0.0
0
100
200
300
400
500
600
700
Time (s)
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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)
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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/Dm = 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
40.8  7.9
51.6  6.1
36.0  4.7
39.2  4.7
38.5  6.7
41.6  5.5
36.2  2.6
39.5  4.7
36.5  4.7
35.1  2.5
39.3  4.2
15.8  1.6
39.2  5.8
CERTIFIED
(39.6)
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(35.5)
38.8
(37.7)
(41)
(36)
(39)
(36)
(35)
(39)
(15.7)
38.57
Relative Diff. (%)
3.0
1.2
1.4
1.0
2.1
1.5
0.56
1.3
1.4
0.29
0.77
0.64 26
1.6
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 (51V+)
Cr (52Cr+)
Co (59Co+)
Ni (60Ni+)
Cu (63Cu+)
W (184W+)
Pb (208Pb+)
Bi (209Bi+)
MEAS.
0.119  0.029
0.073  0.012
0.156  0.017
0.143  0.017
0.248  0.040
0.107  0.027
0.056  0.055
0.0016  0.0032
CERT. (INFO)
0.106
0.066
0.150
0.142
0.250
0.102
0.024
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(0.0009)
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 (51V+)
Cr (52Cr+)
Co (59Co+)
Ni (60Ni+)
Cu (63Cu+)
W (184W+)
Pb (208Pb+)
Bi (209Bi+)
MEAS.
0.115  0.011
0.078  0.036
0.137  0.035
0.139  0.108
0.277  0.201
0.108  0.013
0.021  0.004
0.0006  0.0001
CERT. (INFO)
0.106
0.066
0.150
0.142
0.250
0.102
0.024
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(0.0009)
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Multivariate Analysis
in LA-ICP-MS
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Laser Ablation of NIST 1224 Steel
2500000
end laser
ablation
Signal (counts/s)
2000000
65
Cu+
53Cr
1500000
59Co
60Ni
59
Co+
60
65Cu
53
Cr+
+
Ni
98Mo
1000000
184W
start laser
ablation
signal from
argon blank
500000
98
Mo+
184
W+
0
100
150
200
250
300
350
400
Time (s)
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STEEL SAMPLES
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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
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Comparison of Stainless Steel Washers from the Same Bag
4.0
(16 Elements)
3.5
3.0
Q Residual
2.5
2.0
1.5
1.0
99% C.I.
0.5
95% C.I.
0.0
1
2
3
4
5
6
7
8
9
Sample Number
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Comparison of Two Stainless Steel Washers from the Same Box
(19 elements)
12
99% C.I.
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Q Residual
8
6
4
2
0
1
2
3
4
5
6
7
8
9
Sample Number
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Chemometric Comparison of Seven Carbon Steels
(25 Isotope Model)
9
8
7
Principal Component 2
6
5
4
NIST 1224
3
NIST 1227
2
-10
-9
-8
-7
-6
-5
-4
-3
-2
-1
NIST 1263a
1
NIST 1264a_1
0
NIST 1264a_2
-1
-2
0
1
2
3
4
pipe
bar
plate
-3
-4
-5
-6
-7
-8
Principal Component 3
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Comparison of SRM 139 and 139b to 139a
(20 Elements)
12
SRM139b
SRM139
10
Q Residual
8
6
4
99% C.I.
2
95% C.I.
0
0
2
4
6
8
10
Replicate
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Q Residual
Comparison of Two Strands from a Single Copper Wire
(7 Elements)
10
1
99% C.I.
95% C.I.
0.1
1
2
3
4
5
6
7
8
9
Sample Number
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Copper Wire Comparison
10
Wire 1
Wire 2
Wire 3
Wire 4
Wire 5
Wire 6
99% C.I.
Q Residual
1
0.1
0.01
1E-3
1
2
3
4
5
6
Model Wire
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