SHORT COURSE
ISOTOPIC ANALYSIS USING ICP – MASS SPECTROMETRY
Frank Vanhaecke
Ghent University, Belgium
WHERE EXACTLY IS
BELGIUM?
 Facts
► Area: 30,528 km²
► Population ~ 11,000,000
► Inhabitation density: 360 /km2
► Capital: Brussels
• European Parliament
• NATO headquarters
► Northern part: Flanders (Dutch)
► Southern part: Wallonia (French)
WHERE SHOULD I KNOW BELGIUM FROM?
PERHAPS … WHO KNOWS?
Leo Baekeland?
Chemist, inventor
“Father of plastics”
Bakelite
phenol-formaldehyde resin
Christian de Duve?
Biochemist
Nobel Prize for Medicine in 1974
Discovered lysosomes and peroxisomes
as cell organelles
PERHAPS … WHO KNOWS?
Eddy Merckx ?
1960-70s,
5 times winner of Tour de France
World Champion
World hour record holder
“The cannibal”
Kim Clijsters ?
Recently “retired”
3 times US open, 1 time Australian open
Achieved nr. 1 world ranking
PERHAPS … WHO KNOWS?
Tintin The smurfs
WHERE SHOULD YOU KNOW BELGIUM FROM?
Trappist beers – alcohol content: 6 – 12%
WHERE SHOULD YOU KNOW BELGIUM FROM?
WHAT ABOUT GHENT?
 Wikipedia?
► Ghent started as a settlement at the confluence of the Rivers Scheldt
and Lys and became in the Middle Ages one of the largest and
richest cities of northern Europe. Today it is a busy city with a port
and a university.
THE MIDDLE AGES IN GHENT
GRAVENSTEEN CASTLE (1180)
THE MIDDLE AGES IN GHENT
FRIDAY’S MARKET SINCE 1199 !
THE MIDDLE AGES IN GHENT
GRASLEI – MEDIAEVAL PORT
THE MIDDLE AGES IN GHENT
THE BELFRY & GOTHIC CHURCHES
GHENT UNIVERSITY
°1817 - ~38,000 STUDENTS & ~7,000 STAFF MEMBERS
DEPARTMENT OF ANALYTICAL CHEMISTRY
ATOMIC & MASS SPECTROMETRY RESEARCH GROUP
A&MS
THE ISOTOPIC COMPOSITION OF THE
ELEMENTS
ISOTOPES ?
 Isotopes of an element M:
► same atomic number A
• Same number of protons in their nuclei
• Same number of electrons in their shells
 Identical chemical behaviour
• First approximation – statement will be refined later on
► Different mass number Z
• Different number of neutrons in their nuclei
 Different masses
 Notation
• or
 Terminology?
► Isotope: same place in PSE
► Todd & Soddy (early 20th century)
XA
Z XA
DISCOVERY OF ISOTOPES
 Separation of isotopes according to their mass in MS
► Thomson: separation of Ne+ isotopes in magnetic field
► Later on: Aston → isotopes for a suite of elements
http://www.hibbing.edu/chem/abomb/page_id_64208.html
ISOTOPES?
 Mono-isotopic elements?
► 9Be, 19F, 23Na, 27Al, 31P, 45Sc, 55Mn, 59Co, 75As, 89Y, 93Nb, 103Rh, 127I,
133Cs, 141Pr, 159Tb, 165Ho, 169Tm, 197Au, 209Bi, 231Pa, 232Th
 Other elements?
► 2 – 10 isotopes
► Relative abundances define fraction of element M as nuclide nM
• N: number of atoms
• N: number of moles
 
 
 
 




 mi
1i
i
1
mi
1i
i
1
1
Mn
Mn
MN
MN
M)θ(
THE ISOTOPIC COMPOSITION OF THE ELEMENTS
 First approximation:
all elements show an isotopic composition that is stable in nature
 Why ?
► Thorough mixing during formation of our solar system (4.6 . 109 years BP)
The solar system was formed approximately 4.5 billion
years ago. The material making up the solar system all
came from a single, mostly homogeneous cloud of
material (solar nebula). The matter rotated in a flattened
plane, splayed out in a disk due to the angular
momentum. With time, material not falling to the central
sun, would either be thrown out of the system or begin to
collect and build up planetesimals. At safe relative
distances, planetesimals built up to form the planets.
VARIATIONS IN
THE ISOTOPIC COMPOSITION OF THE ELEMENTS
1. Decay of naturally occurring, long-lived radionuclides
2. Natural fractionation effects
3. Man-made variations
4. Interaction of cosmic rays with terrestrial matter
5. Variations observed in extra-terrestrial materials
RADIOACTIVE DECAY
 Radioactive nuclide: undergoes spontaneous radioactive decay
► -decay:
• Predominantly for heavy nuclides with m > 200
► β –decay
• E distributed over β-particle & (anti)neutrino
• β-particles show continuous E-distribution
► γ-radiation
• Emitted by nucleus in excited state (upon relaxation)
 

4
2
4A
2Z
A
Z YX












YeX:captureelectron
YX:decay
YX:decay
A
1Z
0
1
A
Z
0
1
A
1Z
A
Z
0
1
A
1Z
A
Z [n → p and β-]
[p → n and β+]
[p → n and e-capture from K shell]
RADIOACTIVE DECAY
2/1T
2ln

Characteristic T1/2
t
0t eNN 

RADIOACTIVE DECAY
 Production of daughter nuclide
http://www.earlham.edu/~smithal/radiometric-origins.htm
VARIATIONS IN ISOTOPIC COMPOSITION - DECAY OF
NATURALLY OCCURRING, LONG-LIVED RADIONUCLIDES
 Variations in Sr isotopic composition due to:
► 87Rb = naturally occurring, long-lived radionuclide
• T1/2 = 48.8 x 109 y
• Isotopic composition of Rb has changed through time
• Isotopic composition of Rb presently equal for all terrestrial materials
► Isotopic composition of Sr: variable!
• E.g., rocks: dependent on elemental Rb/Sr ratio + age
 SrRb 8787
Sr isotope Natural range of
relative isotopic abundance
84
Sr 0.55 – 0.58 %
86
Sr 9.75 – 9.99 %
87
Sr 6.94 – 7.14 %
88
Sr 82.29 – 82.75 %
IUPAC, 1997
VARIATIONS IN ISOTOPIC COMPOSITION - DECAY OF
NATURALLY OCCURRING, LONG-LIVED RADIONUCLIDES
B. Bourdon et al, Rev. Miner. Geochem, 52, 1-19, 2003.
► 238U  206Pb
► 235U  207Pb
► 232Th  208Pb
► 204Pb: not radiogenic
VARIATIONS IN ISOTOPIC COMPOSITION - DECAY OF
NATURALLY OCCURRING, LONG-LIVED RADIONUCLIDES
 Variations in the isotopic composition of Pb
► 238U  206Pb; 238U: T1/2 = 4.5 x 109 y
► 235U  207Pb; 235U: T1/2 = 7.1 x 108 y
► 232Th  208Pb; 232Th: T1/2 = 1.4 x 1010 y
► 204Pb = not radiogenic
 Consequences ?
► Isotopic comp. Pb in the presence of U and/or Th changes as f(time)
• Extremely slowly, cf. T1/2
► Isotopic comp. Pb in rocks, dependent on
• Pb/U and Pb/Th elemental ratios
• Time during which elements have “spent together”
► Isotopic comp. Pb varies as a f(place), f(ore deposit), …
Pb isotope Natural range of
relative isotopic abundance
204
Pb 1.04 – 1.65 %
206
Pb 20.84 – 27.48 %
207
Pb 17.62 – 23.65 %
208
Pb 51.28 – 56.21 %
IUPAC, 1997
VARIATIONS IN ISOTOPIC COMPOSITION - DECAY OF
NATURALLY OCCURRING, LONG-LIVED RADIONUCLIDES
Element
containing
radiogenic
nuclide(s)
Isotopes (isotopic abundance
as mole fraction) with
radiogenic nuclides indicated
by the arrow
Parent radionuclide
(T1/2)
Radioactive decay
Nd
142Nd (0.2680-0.2730)
 143Nd (0.1212-0.1232)
144Nd (0.2379-0.2397)
145Nd (0.0823-0.0835)
146Nd (0.1706-0.1735)
148Nd (0.0566—0.0678)
150Nd (0.0553-0.0569)
147Sm (1.06 1011 yrs)  NdSm 143147
VARIATIONS IN ISOTOPIC COMPOSITION - DECAY OF
NATURALLY OCCURRING, LONG-LIVED RADIONUCLIDES
Element
containing
radiogenic
nuclide(s)
Isotopes (isotopic abundance
as mole fraction) with
radiogenic nuclides indicated
by the arrow
Parent radionuclide
(T1/2)
Radioactive decay
Hf
174Hf (0.001619-0.001621)
 176Hf (0.05206-0.05271)
177Hf (0.18593-0.18606)
178Hf (0.27278-0.27297)
179Hf (0.13619-0.13630)
180Hf (0.35076-0.35100)
176Lu (3.57 . 1010 yrs)  
HfLu 176176
there is also a small fraction (3%) of 176Lu that decays to 176Yb via electron capture
VARIATIONS IN ISOTOPIC COMPOSITION - DECAY OF
NATURALLY OCCURRING, LONG-LIVED RADIONUCLIDES
Element
containing
radiogenic
nuclide(s)
Isotopes (isotopic abundance
as mole fraction) with
radiogenic nuclides indicated
by the arrow
Parent radionuclide
(T1/2)
Radioactive decay
Os
184Os (†)
186Os
 187Os
188Os
189Os
190Os
192Os
187Re (4.161 . 1010 yrs)  
OsRe 187187
VARIATIONS IN ISOTOPIC COMPOSITION
NATURAL ISOTOPE FRACTIONATION EFFECTS
 Isotope fractionation?
► Due to their relative difference in mass, different isotopes of the same
element may take part with a (slightly !!) different efficiency in physical
processes or in (bio)chemical reactions.
► Both differences in reaction rate (kinetics) and in equilibrium state
(thermodynamics) have been described.
ISOTOPE FRACTIONATION DURING A PHYSICAL
PROCESS – EVAPORATION OF WATER
 Rayleigh equation
• R = 18O/16O
• ft fraction of water(liq) remaining
• Fractionation factor 
•  approaches 1 at high T
H2O(gas) → isotopically lighter
H2O(liq) → isotopically heavier
 1
t0t fRR 

 
 liquid
1618
vapor
1618
OO
OO

THERMODYNAMIC ISOTOPE FRACTIONATION EFFECT
DISSOCIATION OF A DIATOMIC MOLECULE
F. Vanhaecke et al, JAAS, 24, 863-886, 2009.
21 m
1
m
1
µ
1
µ
k
2
h
2
1
nE









POTENTIAL ENERGY DIAGRAM – CHEMICAL REACTION
ΔG
ΔG < 0: spontaneous reaction
E*
KINETIC ISOTOPE FRACTIONATION EFFECT
CHEMICAL REACTION – ROLE OF ACTIVATION ENERGY
Activated
complex
½ hν(H)*
E(L)*E(H)*
Reactant
½ hν(L)*
½ hν(H)½ hν(L)
Reaction coordinate
E(L)* < E(H)*
Unidirectional reaction
F. Vanhaecke et al, JAAS, 24, 863-886, 2009.
ISOTOPE FRACTIONATION EFFECT
CHEMICAL REACTION
Note: assuming ΔG = ΔH + TΔS  ΔH
VARIATIONS IN ISOTOPIC COMPOSITION
NATURAL ISOTOPE FRACTIONATION EFFECTS
 Extent of isotope fractionation?
► ~ Relative difference between the masses of the isotopes
• More pronounced for light isotopes
• But, discovered for more and more elements owing to higher precision in MS
► ~ Extent to which element takes part in processes
• Physical processes
– Evaporation, condensation
– Diffusion
– …
• (Bio)chemical reactions
 Also mass-independent isotope fractionation (rare)
► Difference in size between nuclei of isotopes
• Not always linear relation with mass
► Hyperfine coupling between nuclear spin & electron cloud
VARIATIONS IN ISOTOPIC COMPOSITION
NATURAL FRACTIONATION EFFECTS
 Very small effects
► Special notation introduced
 
000,10
O
O
O
O
O
O
Oε
000,1
O
O
O
O
O
O
00
0Oδ
dardtans
16
18
dardtans
16
18
sample
16
18
18
dardtans
16
18
dardtans
16
18
sample
16
18
18








































VARIATIONS IN ISOTOPIC COMPOSITION
NATURAL FRACTIONATION EFFECTS
VARIATIONS IN ISOTOPIC COMPOSITION
NATURAL FRACTIONATION EFFECTS
Factor 2 relative difference between isotope masses
10% relative difference between isotope masses
6% relative difference between isotope masses
Difference too small for measurable isotope fractionation ?
VARIATIONS IN ISOTOPIC COMPOSITION
NATURAL FRACTIONATION EFFECTS
Difference too small for measurable isotope fractionation ?
Fractionation reported for increasing number of (heavier) elements: improved MS precision
von Blanckenburg et al.
VARIATIONS IN ISOTOPIC COMPOSITION
MAN-MADE VARIATIONS
mined uranium
0.715% 235U and 99.28% 238U
isotopic
enrichment
fission reactor
fuel enriched in 235U
waste =
depleted U (DU)
depleted in 235U
very high density !
counterweights in airplanes
ammunition & projectiles
penetrating armored steel
VARIATIONS IN ISOTOPIC COMPOSITION
MAN-MADE VARIATIONS
 Enrichment of B in 10B:
► 10B thermal neutron cross-section 6 x higher than that of 11B
• Control of chain reaction in nuclear fission reactor
• Boron neutron capture theory (BNCT)
 BNCT: experimental anti-cancer therapy
► Administration of 10B-containing drug
• Selective accumulation in tumoral (neoplastic) tissue
► Irradiation with thermal neutrons
• 10B undergoes (n,) reaction and is converted into 7Li
► -particle only travels distance ≈ one cell
• Damage limited to cell wherein process takes place
MAN-MADE VARIATIONS IN ISOTOPIC COMPOSITION
BORON NEUTRON CAPTURE THERAPY
► Less damage to healthy than to neoplastic tissue
VARIATIONS IN ISOTOPIC COMPOSITION
INTERACTION OF COSMIC RAYS WITH TERRESTRIAL MATTER
 Formation of 14C in the atmosphere
► Cosmic rays
► Spalliation
► Production of neutron
► 14N + n → 14C + p
 14C
► Radionuclide
► T1/2 = 5730 y
► Production & decay in dynamic equilibrium
► Constant abundance of 14C, next to 12C & 13C
 Also other “cosmogenic” nuclides formed
► Stable nuclides & radionuclides
► Extremely low concentrations
► In the atmosphere
► On the earth’s surface (to a lesser extent)
VARIATIONS IN ISOTOPIC COMPOSITION – VARIATIONS
OBSERVED IN EXTRA-TERRESTRIAL MATERIALS
 Extraterrestrial materials ?
In extraterrestrial materials, some elements show
an isotopic composition not known in terrestrial materials
Many iron meteorites display an enrichment in 107Ag unseen in any terrestrial silver. It is now widely
accepted that the 107Ag enrichment is a result of the decay of the now extinct radionuclide 107Pd (T1/2 =
6.5 x 106 y). Since Pd is more siderophile than Ag, “core” formation results in high Pd/Ag elemental
ratios, as displayed in iron meteorites (these meteorites are often considered a good “model” for the
planetesimals). Terrestrial material that is accessible on the other hand (the silicate fraction) is
characterized by much lower Pd/Ag elemental ratios. Therefore, in all terrestrial material, the 107Ag/109Ag
isotope ratio is (very close to) 1.081. In some iron meteorites however, the 107Ag/109Ag isotope ratio can
substantially deviate from this value (values up to 9 has been reported!).
Hoba meteorite, Namibia (50 ton)Iron meteorite (5% of meteorites)
HOW TO MEASURE ISOTOPE RATIOS –
SINGLE-COLLECTOR ICP-MS INSTRUMENTS
IMPORTANCE OF ISOTOPE RATIO PRECISION
IsotoperatioIsotoperatio
?
2 different populations

conclusions!
…
WHAT CAN WE EXPECT IN TERMS OF
ISOTOPE RATIO PRECISION ?
 Ultimate limit set by counting statistics
 Poisson counting statistics
► Valid if variation in arrival of ions @ detector = statistically governed
► Then
• N = total # counts (not count rate!)
 Ultimate limit?
► Importance of acquiring a high number of counts
• Sufficiently high signal intensities
• Sufficiently long measurement times
“TRADITIONAL” QUADRUPOLE-BASED ICP-MS
HOW TO GET THE BEST ISOTOPE RATIO PRECISION?
“TRADITIONAL” QUADRUPOLE-BASED ICP-MS
 Optimum conditions?
► Sufficiently high signal intensities
• Cf. detector dead time
► Sufficiently long measurement time
► Isotope ratio close to 1
 Problem?
► ICP = noisy source
 Warning
► Do not compare apples & pears
► St. dev (mean) = st. dev. / SQR = st. error
HOW TO GET THE BEST ISOTOPE RATIO PRECISION?
“TRADITIONAL” QUADRUPOLE-BASED ICP-MS
sufficiently high total acquisition time
cf. Poisson counting statistics
pneumatic nebulization
87Sr/86Sr
laser ablation
F. Vanhaecke et al, JAAS, 14, 1691-1696, 1999.
M. Resano et al, JAAS, 23, 1182-1191, 2008.
HOW TO GET THE BEST ISOTOPE RATIO PRECISION?
“TRADITIONAL” QUADRUPOLE-BASED ICP-MS
1 2 3 4 5 6 7 8 9 10
Time (arbitrary units)
250
270
290
310
330
350
370
390
signal intensity
0
0.2
0.4
0.6
0.8
1
1.2
Isotope ratio
isotope 1
isotope 2
HOW TO GET THE BEST ISOTOPE RATIO PRECISION?
“TRADITIONAL” QUADRUPOLE-BASED ICP-MS
1 2 3 4 5 6 7 8 9 10
Time (arbitrary units)
250
270
290
310
330
350
370
390
signal intensity
0
0.2
0.4
0.6
0.8
1
1.2
Isotope ratio
isotope 1
isotope 2
HOW TO GET THE BEST ISOTOPE RATIO PRECISION?
“TRADITIONAL” QUADRUPOLE-BASED ICP-MS
 Residence time / acquisition point
► Sufficiently low
► Too low values?
• Large fraction of time lost
• Settling time
HOW TO GET THE BEST ISOTOPE RATIO PRECISION?
“TRADITIONAL” QUADRUPOLE-BASED ICP-MS
 An example of data acquisition conditions:
► Scanning mode
• Peak hopping/jumping
► Dwell time / acquisition point (per sweep)
• 10 ms
► Number of acquisition points / spectral peak
• 1
► Number of sweeps per replicate measurement
• 3250
► Total acquisition time per replicate measurement
• ~3 min
► Number of replicate measurements
• 10
 Optimum measurement precision? ~0.1 % RSD
DIFFERENT ACQUISITION TIMES
FOR DIFFERENT ISOTOPES ?
 Sometimes used
► Higher # of counts accumulated for low-abundant isotope
• Cf. Poisson counting statistics
► Lower scan speed
• Cf. noisy source
► Compromise conditions
QUADRUPOLE-BASED ICP-MS
IMPROVEMENT WITH A COLLISION/REACTION CELL
 Use of Ne as non-reactive collision gas in DRC
► Mixing of ions sampled at slightly different moments in time
► Collisional damping  improved isotope ratio precision
L. Moens et aI, JAAS, 16, 991–994, 2001.
QUADRUPOLE-BASED ICP-MS
IMPROVEMENT WITH A COLLISION/REACTION CELL
 Use of Ne as non-reactive collision gas in DRC
► Mixing of ions sampled at slightly different moments in time
► Collisional damping  improved isotope ratio precision
Increased
mass discrimination
Improved
isotope ratio precision
laser ablation
M. Resano et al, JAAS, 23, 1182-1191, 2008.
QUADRUPOLE-BASED ICP-MS
EQUIPPED WITH A COLLISION/REACTION CELL
 Other guidelines are still valid
► Low dwell time / acquisition point
► 1 acquisition point / spectral peak
► Acquiring a sufficiently high # of pulses
• Sufficiently high target element concentration
• Sufficiently long measurement time per replicate
L. Moens et aI, JAAS, 16, 991–994, 2001.
SECTOR FIELD ICP – MASS SPECTROMETRY
Selection of resolution setting R = 300, 4000 or 10000
MRHR
LR
0
500
1000
1500
2000
2500
0 10 20 30 40 50 60
mass/charge (arbitrary units)
signalintensity
analyte ion + molecular ion
SECTOR FIELD ICP – MASS SPECTROMETRY
IMPROVED ISOTOPE RATIO PRECISION AT LOW R
 Optimum measurement precision? ~0.025 – 0.05% RSD
HOW ARE FLAT-TOPPED PEAKS OBTAINED ?
Wide exit slit
Scanning
Width of ion beam
<
Exit slit width
HOW ARE FLAT-TOPPED PEAKS OBTAINED ?
Wide exit slit
Scanning
Width of ion beam
<
Exit slit width
HOW ARE FLAT-TOPPED PEAKS OBTAINED ?
Wide exit slit
Scanning
Width of ion beam
<
Exit slit width
SECTOR FIELD ICP – MASS SPECTROMETRY
IMPROVED ISOTOPE RATIO PRECISION AT LOW R
 Vanhaecke et al., Anal. Chem., 567-569, 68, 1996
! central section of
flat-topped peak
SECTOR FIELD ICP – MASS SPECTROMETRY
IMPROVED ISOTOPE RATIO PRECISION AT LOW R
 Vanhaecke et al., Anal. Chem., 567-569, 68, 1996
SECTOR FIELD ICP – MASS SPECTROMETRY
ISOTOPE RATIO PRECISION AT MEDIUM R ?
0
500
1000
1500
2000
2500
0 10 20 30 40 50 60
mass/charge (aribitray units)
signalintensity
analyte ion + molecular ion
0
50
100
150
200
250
0 10 20 30 40 50
mass/charge (arbitrary units)
signalintensity
analyte ion
molecular ion
flat-topped peaks
RSD% ≤ 0.05%
“triangular” peaks
RSD% ≥ 0.1%
SECTOR FIELD ICP – MASS SPECTROMETRY
ISOTOPE RATIO PRECISION AT MEDIUM R ?
 Vanhaecke et al., Anal. Chem., 268-273, 69, 1997
!
SECTOR FIELD ICP – MASS SPECTROMETRY
ISOTOPE RATIO PRECISION AT MEDIUM R ?
 Vanhaecke et al., Anal. Chem., 268-273, 69, 1997
SECTOR FIELD ICP – MASS SPECTROMETRY
ISOTOPE RATIO PRECISION AT MEDIUM R ?
 Vanhaecke et al., Anal. Chem., 268-273, 69, 1997
multiplication factor: 107 – 108 / pulse counting mode vs. analog mode
ION DETECTION VIA ELECTRON MULTIPLIER
DETECTOR DEAD TIME
EM OPERATED IN PULSE COUNTING MODE
 Handling of one ion  no possibility to detect another one
► 10 – 100 ns
 More pronounced effects at higher count rates
 Accurate isotope ratio (≠ 1) determination requires correction
 Correction for non-paralyzable detector:
 Experimental determination of dead time (τ) required
► Various methods for determination
• Do not forget to set τ = 0 in software prior to experimental determination
► Detector dead time  instrument software for automatic correction
DETERMINATION OF DETECTOR DEAD TIME
Normalized 208Pb/207Pb isotope ratio (= (208Pb/207Pb)measured/(208Pb/207Pb)true value) plotted as a
function of the value applied for dead time correction of the ‘raw’ results obtained for solutions
with a Pb concentration ranging from 20 to 45 µg/L. In this particular case, the dead time of
the detection system was observed to be  20 ns.
F. Vanhaecke et al, JAAS, 13, 567–571, 1998.
DETERMINATION OF DETECTOR DEAD TIME
Variation of the 204Pb/208Pb isotope ratio
as a function of the Pb concentration
for various assumed values of detector dead time.
S. M. Nelms et al, JAAS, 16, 333-338, 2001.
DETERMINATION OF DETECTOR DEAD TIME
Slope of the curve obtained on plotting the 204Pb/208Pb isotope ratio vs. the Pb concentration
as a function of the assumed value for the detector dead time. The intersection of the line thus
obtained with the x-axis provides the actual dead time.
S. M. Nelms et al, JAAS, 16, 333-338, 2001
PRECISION, PRECISION, WHAT ABOUT ACCURACY ?
MASS DISCRIMINATION IN ICP-MS
ICP-MS
 Mass discrimination
► Measured ratio  true value
► Order of magnitude
• ca. 1% per mass unit @ mid-mass
• Considerably larger @ low masses
► Not a systematic f(time)
TIMS
 NOT = mass fractionation !
► TIMS
► First
• measurement result < true value
► Later on:
• measurement result > true value
F. Albarede and B. Beard, Rev. Miner. Geochem., 55, 113–150, 2004.
SPACE-CHARGE EFFECTS IN THE ICP-MS INTERFACE
 All ions forced to move with vAr (collisions)
► Ekin = ½ mv2 and hence, f(mion)
 Electrostatic repulsion between positively charged ions
► Defocusing of ion beam
► Lighter ions preferentially lost
MASS DISCRIMINATION CORRECTION IN
SINGLE-COLLECTOR ICP-MS
External correction
Based on comparison of experimental result
and certified value for isoropic reference material
Preferably via bracketing (std – sample – std – sample – …)
0,95
1
1,05
1,1
1,15
1,2
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
isotopic standard sample
Measurement number
Isotope ratio result
MASS DISCRIMINATION CORRECTION IN
SINGLE-COLLECTOR ICP-MS
Internal correction – type I
If at least one isotope ratio of the target element is constant in nature
E.g., Sr: isotopic composition displays natural variation, but 86Sr/88Sr = constant
Comparison of experimental result and certified value for 86Sr/88Sr
Calculation of correction factor ε or , to be used for further correction
 
 
 mΔε
obs
true
mΔ
power
obs
true
linear
obs
true
onentialexp
e
R
R
K
ε1
R
R
K
mΔε1
R
R
K




β
2
1
obs
true
m
m
R
R
K 






Various approaches lead to similar results
(no significant differences)
MASS DISCRIMINATION CORRECTION IN
SINGLE-COLLECTOR ICP-MS
 
 
 mΔε
obs
true
mΔ
power
obs
true
linear
obs
true
onentialexp
e
R
R
K
ε1
R
R
K
mΔε1
R
R
K




β
2
1
obs
true
m
m
R
R
K 






Various approaches lead to similar results
(no significant differences)
Internal correction – type II
Using an element, close in mass number, added to the sample
E.g., Tl added to sample solutions intended for Pb isotopic analysis
Comparison of experimental result and certified value for 203Tl/205Tl
Calculation of correction factor ε or , to be used for further correction
ISOTOPE RATIO PRECISION WITH ICP-MS
(OPTIMUM VALUES)
 Applications
► Induced variations  single-collector
► Natural variations due to radiogenic nuclide
• Geochronological dating  multi-collector
• Provenance determination  single- & multi-collector
► Natural variations due to fractionation  multi-collector
► Natural variations due to extinct radionuclides  multi-collector
Type of ICPMS instrument Internal isotope ratio precision (RSD)
Traditional quadrupole-based ICPMS ≥ 0.1%
Quadrupole-based ICPMS
with pressurized collision/reaction cell
≥ 0.025%
Single-collector sector field ICPMS ≥ 0.025% at LR and ≥ 0.1% at MR
Multi-collector ICPMS ≥ 0.002% at LR and ≥ 0.005% at MR
INDUCED VARIATON
ELEMENTAL ASSAY VIA ISOTOPE DILUTION
PRINCIPLE OF ISOTOPE DILUTION (ID)
sample + =spike mixture
0
5
10
15
20
25
signal isotope 1
signal isotope 2
Rsample = 2.125
Rtracer = 0.208
Rblend = 0.688
PRINCIPLE OF ISOTOPE DILUTION (ID)
sample spike mixture
mixture = known amount of sample + known amount of spike
spike : different isotopic composition
determination of ratio (enriched isotope / reference isotope) in:
sample
spike
mixture
Isotope ratios:much more more “robust” than signal intensities !
ELEMENTAL ASSAY USING ISOTOPE DILUTION
)1(
n
n
n.)1(n
n.
RR
RR
.
R
R
n
R
n
R
n
nn
R
ninenrichedspike
nn
nn
R
n
n
R
n
n
R
sample
sample
1
sample
spikespikespike
1
spike
1
samplemixture
mixturespike
spike
sample
sample
1
spike
spike
1
sample
sample
1
spike
1
sample
1
mixture
1
spike
2
sample
2
spike
1
sample
1
mixture
spike
2
spike
1
spike
sample
2
sample
1
sample




















ELEMENTAL ASSAY USING ISOTOPE DILUTION
spikesamplemixture R.RRoptimum 
)2(
n
nandn.)2(n
n.
RR
RR
n
ninenrichedspike
n.)1(n
n.
RR
RR
.
R
R
n
ninenrichedspike
nn
nn
R
n
n
R
n
n
R
sample
sample
2
samplespikespikespike
2
spike
2
samplemixture
mixturespike
sample
2
2
spikespike
1
spike
1
samplemixture
mixturespike
spike
sample
samp
1
1
spike
2
sample
2
spike
1
sample
1
mixture
spike
2
spike
1
spike
sample
2
sample
1
sample




























ELEMENTAL ASSAY USING ISOTOPE DILUTION
 Advantages
► After isotopic equilibration: analyte losses do no affect result
► Isotope ratios barely affected by changes in sensitivity (matrix effects)
► Most reliable calibration method
• High accuracy
• High precision
 Disadvantages
► Not suited for mono-isotopic elements
• Be, Na, Al, P, K, Sc, Mn, Co, As, Y, Nb, Rh, I, Cs, Pr, Ho, Tm, Au, Bi, Th
– Sometimes : use of long-lived radionuclide (e.g., 129I)
► High purchase price of spikes
•  1000 € / 100 mg
– Isotopic enrichment & nuclide (natural isotopic abundance)
► Analyte concentration has to be approximately known
 Use of IDMS ?
► Reference measurements
► Analyte losses to be expected
DETERMINATION OF ULTRA-TRACE AMOUNTS OF
FE IN AGNO3 SOLUTIONS
 Goal?
►Determination of Fe in AgNO3 solutions
• Ag-matrix: ~ 600 g.L-1 Ag
• memory effects & signal suppression
►ICP-MS: max. ~ 100 mg.L-1 Ag
• dilution of the samples (external calibration)
• LOD = 1200 ng.g-1
► precipitation of Ag as AgBr
• co-precipitation of Fe?
• isotope dilution as a calibration method
L; Balcaen et al, ABC, 377, 1020-1025, 2003..
DETERMINATION OF FE IN AGNO3 SOLUTIONS
PRECIPITATION OF AG+ AS AGBR + ID
precipitation of Ag Filtration
Ag-content: ± 1 mg.L-1
!! CONTAMINATION !!
54Fe spike HBr
AgNO3
Dilution (50x)
L; Balcaen et al, ABC, 377, 1020-1025, 2003..
DETERMINATION OF FE IN AGNO3 SOLUTIONS
SPECTRAL INTERFERENCES
54Fe
(5,85 %)
56Fe
(91,8 %)
57Fe
(2,12 %)
58Fe
(0,28 %)
Isobaric
nuclide
54Cr+ 58Ni+
Ar-containing
molecular ion
40Ar14N+
38Ar16O+
36Ar18O+
40Ar16O+ 40Ar16OH+
38Ar18OH+
40Ar18O+
Ca-containing
molecular ion
40Ca16O+ 40Ca16OH+ 40Ca18O+
42Ca16O+
Cl-containing
molecular ion
37Cl16OH+ 23Na35Cl+
L; Balcaen et al, ABC, 377, 1020-1025, 2003..
DETERMINATION OF FE IN AGNO3 SOLUTIONS
OVERCOMING SPECTRAL OVERLAP VIA CHEMICAL RESOLUTION
PerkinElmer-SCIEX
Dynamic Reaction Cell
ICP-MS
Use of NH3 to induce selective ion-molecule reactions
allowing spectral overlap to be overcome at m/z = 54 & 56
L; Balcaen et al, ABC, 377, 1020-1025, 2003..
DETERMINATION OF FE IN AGNO3 SOLUTIONS
OVERCOMING SPECTRAL OVERLAP VIA CHEMICAL RESOLUTION
S/B ratio
50 µg/L Fe std sol’n
1 mg/L Ca std sol’n
m/z = 56
L; Balcaen et al, ABC, 377, 1020-1025, 2003..
DETERMINATION OF ULTRA-TRACE AMOUNTS OF
FE IN AGNO3 SOLUTIONS
 Comparison of LODs
►Dilution of sample solution  1200 ng/g
►AgBr precipitation + ID  10 ng/g
L; Balcaen et al, ABC, 377, 1020-1025, 2003..
ISOTOPE DILUTION
IN ELEMENTAL SPECIATION ANALYSIS?
 Speciation analysis?
► Separation, identification, quantification of the different chemical
forms (oxidation state, molecule) in which the target element occurs
• Examples
– Cr(III) vs. Cr(VI)
– Different toxic & non-toxic As-containing compounds
– Inorganic Hg vs. MeHgX
– …
► Combination of separation technique with ICP-MS
• Separation technique
– Liquid chromatography – HPLC
– Gas chromatography – GC
– Field flow fractionation – FFF
– Capillary electrophoresis – CE
• ICP-MS as element-selective & sensitive detector
ISOTOPE DILUTION IN ELEMENTAL SPECIATION ANALYSIS
SPECIES-SPECIFIC ISOTOPE DILUTION
 What?
► Synthesis of specific compound with non-natural isotopic composition
► Addition of this compound to sample
• As early as possible in the analysis process
 Advantages ?
► Automatic correction for:
• Non-quantitative derivatization (if relevant, e.g., GC-ICP-MS)
• Non-quantitative extraction (if relevant, e.g., SPME)
• Non-quantitative column recovery
• Variations in ICP-MS sensitivity due to
– Matrix effects
– Gradient elution
– Signal drift
– Instrument instability
– …
► Important remark
• No correction for non-quantitative recovery out of solid matrix
ISOTOPE DILUTION IN ELEMENTAL SPECIATION ANALYSIS
SPECIES-UNSPECIFIC ISOTOPE DILUTION
 When ?
►No standards available
• Identity of species not known
• Too many species to synthesize them all
• Species too complicated to synthesize
• Synthesis of standards too labour-intensive and/or time-consuming
 Advantages ?
►Automatic correction for changes in ICP-MS sensitivity
• Gradient elution
• Matrix changes as f(time)
• Signal instability & drift
ISOTOPE DILUTION IN ELEMENTAL SPECIATION ANALYSIS
SPECIES-UNSPECIFIC ISOTOPE DILUTION
4°C
nebulizer gas
waste
pumps
nebulizer
torchO2
MS
RP-column
injector
mixing chamber
spike
4°C
nebulizer gas
waste
pumps
nebulizer
torchO2
MS
RP-column
injector
mixing chamber
spike
2 °C
Continuous & calibrated flow of Br-81
Meermann et al. ABC, 402, 439-448, 2012
BR-CONTAINING DRUG: HPLC-ICP-MS METABOLITE PROFILING
QUANTIFICATION VIA SPECIES UNSPECIFIC ISOTOPE DILUTION
0
20000
40000
60000
80000
100000
120000
140000
160000
180000
200000
0 1000 2000 3000 4000 5000 6000
time (s)
Intensity(cps)
79Br
81Br
F. Cuyckens et al, ABC 390, 1717–1729, 2008.
BR-CONTAINING DRUG: HPLC-ICP-MS METABOLITE PROFILING
QUANTIFICATION VIA SPECIES UNSPECIFIC ISOTOPE DILUTION
Via ID formula 
mass flow chromatogram
0
2
4
6
8
10
12
35 40 45 50 55 60
time (min)
81
Br/79
Br
81Br / 79Br
Rnat  1
Rspike  9
F. Cuyckens et al, ABC 390, 1717–1729, 2008.
BR-CONTAINING DRUG: HPLC-ICP-MS METABOLITE PROFILING
QUANTIFICATION VIA SPECIES UNSPECIFIC ISOTOPE DILUTION
Mixture of standards
mass flow chromatogram

µg Br /s
F. Cuyckens et al, ABC 390, 1717–1729, 2008.
INDUCED VARIATION
TRACER EXPERIMENTS WITH STABLE
ISOTOPES
TRACER EXPERIMENTS FOR STUDYING
THE UPTAKE OF ZN BY DAPHNIA MAGNA
 Usual assumption:
►Toxicity caused by waterborne metal only
• Uptake via gills (A)
►Effect of dietary metals ignored
• Uptake via alimentary channel (B)
 Our study:
►Effects of dietary Zn ?
• Exposure experiment (total Zn / ICP-MS)
• Reprocductive toxicity
►Relative importance of both exposure routes ?
• Stable isotopic tracer experiment (ICP-MS)
A
B
TRACER EXPERIMENTS FOR STUDYING
THE UPTAKE OF ZN BY DAPHNIA MAGNA
Zn2+(aq)
68ZnZn isotopic analysis
using sector field ICP-MS
At R = 4000
67Zn
L. Balcaen et al, ABC, 390, 555–569, 2008.
TRACER EXPERIMENTS FOR STUDYING
THE UPTAKE OF ZN BY DAPHNIA MAGNA
Zn2+(aq)
+ excess 68Zn-EDTA
to minimize effect of 67Zn leaching
from algae
68Zn
67Zn
L. Balcaen et al, ABC, 390, 555–569, 2008.
TRACER EXPERIMENTS FOR STUDYING
THE UPTAKE OF ZN BY DAPHNIA MAGNA
0%
20%
40%
60%
80%
100%
Isotopicabundance(%)
502 566 571 576 581
Sample number
70
68
67
66
64
algae:
67
Zn
algae:
67
Zn algae:
67
Zn algae:
67
Znnatural
Zn
water:
70 µg/L
68
Zn +
EDTA
water:
70 µg/L
68
Zn
water:
150 µg/L
68
Zn
water:
300 µg/L
68
Zn
L. Balcaen et al, ABC, 390, 555–569, 2008.
NATURAL VARIATION
MULTI-COLLECTOR ICP – MASS SPECTROMETRY
Isotope ratio precision:
down to 0,002 % RSD !
ARRAY OF FARADAY COLLECTORS:
SIMULTANEOUS MONITORING OF ION SIGNAL INTENSITIES
1 2 3 4 5 6 7 8 9 10
measurementnumber
250
270
290
310
330
350
370
390
signal intensity
0
0.2
0.4
0.6
0.8
1
1.2
Isotope ratio
isotope 1
isotope 2
isotope ratio
 Simultaneous monitoring:
► Automatic correction for signal instability & signal drift
► Higher isotope ratio precision
 With ICP-MS instrument equipped with only one detector:
► Mimicked by fast ‘hopping’
Isotope ratio precision:
down to 0,002 % RSD !
ION BEAMS  FARADAY COLLECTORS ?
Zoom optics
Moveable detectors
(motorized)
The ion beams are steered into the appropriate
collectors by applying suitable voltages on the zoom
“optics” (= electrostatic lenses).
The position of the Faraday collectors can
be optimised with respect to the respective
ion beams
Or a combination of both …
FARADAY COLLECTOR – OPERATING PRINCIPLE
VR = 1011 Ω
ion beam
e
Compared to electron multiplier:
► Analog amplifier
► Less sensitive
► No detector dead time
► Very long lifetime
MULTI-COLLECTOR ICP – MASS SPECTROMETRY
 Dedicated tool for highly precise isotopic analysis
 Competitor for thermal ionization mass spectrometry – TIMS
 Advantages compared to TIMS ?
► Ion source operated at atmospheric pressure
• Straightforward sample introduction
– Contnuous pneumatic nebulization
– Laser ablation (bulk & spatially resolved analysis of solid samples)
► High ionization efficiency
– TIMS: formation of M+ ions limited to elemnts with IE < 7.5 eV
► Higher sample throughput
► Isolation of target element not required ??
MASS DISCRIMINATION IN
MULTI-COLLECTOR ICP – MASS SPECTROMETRY
 Same phenomenon as in single-collector ICP-MS
 Due to high precision:
► Matrix exerts measurable influence on mass discrimination
 isolation of analyte element
► Analyte concentration exerts influence on mass discrimination
 Matching of target element concentrations within  30%
MASS DISCRIMINATION CORRECTION IN
MULTI-COLLECTOR ICP-MS
If high precision & accuracy is required:
Isolation of target element – pure & quantitative
Matching of element concentration in samples & standards within ± 30%
External correction
Based on comparison of experimental result and certified value for isoropic
reference material
Bracketing (std – sample – std – sample – …)
Internal correction – type I
If at least one isotope ratio of the target element is constant in nature
E.g., Sr: isotopic composition displays natural variation, but 86Sr/88Sr = constant
Comparison of experimental result and certified value for 86Sr/88Sr
Calculation of correction factor ε or , to be used for further correction
Internal correction – type II
Using an element, close in mass number, added to the sample
E.g., Tl added to sample solutions intended for Pb isotopic analysis
Comparison of experimental result and certified value for 203Tl/205Tl
Calculation of correction factor ε or , to be used for further correction
 
 
 mΔε
obs
true
mΔ
power
obs
true
linear
obs
true
onentialexp
e
R
R
K
ε1
R
R
K
mΔε1
R
R
K




β
2
1
obs
true
m
m
R
R
K 






Linear law model
Power law model
Exponential law model
Russell’s equation
Significantdifferences!!
MASS DISCRIMINATION CORRECTION IN
MULTI-COLLECTOR ICP-MS
INTERNAL MASS DISCRIMINATION CORRECTION IN
MULTI-COLLECTOR ICP-MS
 Application of various correction methods
► Will result in relatively small differences
► Significant threat in precise isotope ratio work
► Still issue of discussion between specialists
110/111
Rexp/Rtrue
110/112
Rexp/Rtrue
110/113
Rexp/Rtrue
110/114
Rexp/Rtrue
110/116
Rexp/Rtrue
No MD 1 1 1 1 1
MD according to linear
law (εlin = 0.01)
0.99010 0.98039 0.97087 0.96154 0.94340
MD according to power
law (εpower = 0.01)
0.99010 0.98030 0.97059 0.96098 0.94205
MD according to expontial
law (εexp = 0.01)
0.99005 0.98020 0.97045 0.96079 0.94176
MD according to Russell’s
equation (β = -1.11053)
0.99000 0.98019 0.97056 0.96111 0.94272
Internal correction – type II
Tl added to sample solutions intended for Pb isotopic analysis
Further refinement: deduction of correction factor  (Pb) via  (Tl)
Linear relationship between  (Pb) and  (Tl) defined via reference solutions
INTERNAL MASS DISCRIMINATION CORRECTION IN
MULTI-COLLECTOR ICP-MS
SPECTRAL INTERFERENCES IN
MULTI-COLLECTOR ICP – MASS SPECTROMETRY?
 Usually: target element isolated from matrix
► Clean-up of spectrum
► No analyte isolation in case of laser ablation for sample introduction
 Ar introduced @ 20 L/min in ICP
► Ar+
► Ar2+
► Ar-containing molecular ions – ArH+, ArN+, ArO+, ArOH+, …
 Isotope ratio determination
► At least two nuclides free from spectral overlap
 High precision
► Down to 0.002% RSD
► Limited contribution of interfering ion, already dramatic !
• In contrast to situation for element determination …
FULL HIGH RESOLUTION
IN MULTI-COLLECTOR ICP-MS?
0
500
1000
1500
2000
2500
0 10 20 30 40 50 60
mass/charge (aribitray units)
signalintensity
analyte ion + molecular ion
Low R
High R
Single-collector ICP-MS Multi-collector ICP-MS
0
50
100
150
200
250
0 10 20 30 40 50
mass/charge (arbitrary units)
signalintensity
analyte ion
molecular ion
Deteriorated isotope
ratio precision !
PSEUDO-HIGH RESOLUTION IN MULTI-COLLECTOR ICP-MS
THE BEST OF TWO WORLDS
0
500
1000
1500
2000
2500
0 10 20 30 40 50 60
mass/charge (aribitray units)
signalintensity
analyte ion + molecular ion
0
100
200
300
400
500
600
700
0 10 20 30 40 50 60
mass/charge (arbitrary units)
signalintensity
analyte
ion
analyte ion +
molecular ion
molecular
ion
Low mass R
down to 0.002% RSD
Pseudo high mass R
reduced entrance slit width
exit slit width not changed
Interference-free measurement
down to 0.005% RSD
MASS SPECTRAL PEAK SHAPE
PSEUDO-HIGH MASS RESOLUTION
Wide exit slit
Narrow entrance slit
Only side moved !
Scanning
Analyte ion
Interfering ion only
MASS SPECTRAL PEAK SHAPE
PSEUDO-HIGH MASS RESOLUTION
Wide exit slit
Analyte ion
Interfering ion only
Narrow entrance slit
Only side moved !
Scanning
MASS SPECTRAL PEAK SHAPE
PSEUDO-HIGH MASS RESOLUTION
Wide exit slit
Narrow entrance slit
Only side moved !
Scanning
Analyte ion
Interfering ion only
MASS SPECTRAL PEAK SHAPE
PSEUDO-HIGH MASS RESOLUTION
Wide exit slit
Narrow entrance slit
Only side moved !
Scanning
Analyte ion
Interfering ion only
MASS SPECTRAL PEAK SHAPE
PSEUDO-HIGH MASS RESOLUTION
Wide exit slit
Analyte ion
Interfering ion only
Narrow entrance slit
Only side moved !
Scanning
MASS SPECTRAL PEAK SHAPE
PSEUDO-HIGH MASS RESOLUTION
Scanning
Analyte ion
Interfering ion only
Wide exit slit
Narrow entrance slit
Only side moved !
MASS SPECTRAL PEAK SHAPE
PSEUDO-HIGH MASS RESOLUTION
Scanning
Analyte ion
Interfering ion only
Wide exit slit
Narrow entrance slit
Only side moved !
MASS SPECTRAL PEAK SHAPE
PSEUDO-HIGH MASS RESOLUTION
ScanningAnalyte ion
Interfering ion only
Wide exit slit
Narrow entrance slit
Only side moved !
PSEUDO-HIGH RESOLUTION IN MULTI-COLLECTOR ICP-MS
EXAMPLE: MEASUREMENT OF FE ISOTOPE RATIOS
Interference-free measurement of Fe isotope ratios
Static multi-collection at m/z values where only
analyte ions contributes to signal intensity
Static collectionSpectral scan
S. Weyer, & J.B. Schwieters, Int. J. Mass Spectrom., 226, 355–368, 2003
NATURAL VARIATION
APPLICATIONS BASED ON RADIOGENIC NUCLIDES
NATURAL VARIATIONS IN THE ISOTOPIC COMPOSITION OF SR
 Variations in Sr isotopic composition due to:
► 87Rb = naturally occurring, long-lived radionuclide
• T1/2 = 48.8 x 109 y
• Isotopic composition of Rb has changed through time
• Isotopic composition odf Rb presently equal for all terrestrial materials
► Isotopic composition of Sr: variable!
• E.g., rocks: dependent on elemental Rb/Sr ratio + age
 SrRb 8787
Sr isotope Natural range of
relative isotopic abundance
84
Sr 0.55 – 0.58 %
86
Sr 9.75 – 9.99 %
87
Sr 6.94 – 7.14 %
88
Sr 82.29 – 82.75 %
IUPAC, 1997
NATURAL VARIATIONS IN THE ISOTOPIC COMPOSITION OF SR
 Pronounced variation!
► Measurable by
• TIMS
• MC-ICP-MS
• Single-collector ICP-MS
 Sr isotopic analysis useful for:
► Provenance determination
• Agricultural products
– Wine, cheese, …
• Human remains
– Archeological findings
– Forensics
• …
► Geological dating - Rb-Sr dating
quite often with single-collector ICP-MS
very seldom with single-collector ICP-MS
RADIOMETRIC DATING
based on half-life (T1/2) of radionuclide
and ratio of parent nuclide to daughter nuclide
RB-SR DATING
 Possibilty for dating (t-determination)
► Igneous & metamorphic rocks, via
• Rb-rich minerals they contain
• whole rock dating
► Production of 87Sr as function(t):
► Absolute isotope amounts are difficult to determine accurately
► Divide left & right side by 86Sr
• Note: 86Sr does not vary as function(t)
► Resolve equation for t:
11
2/1
9
2/1
8787
1042.1
T
2ln
λor,y108.48Twith,νβSrRb 

  )1e(RbSrSr tλ87
i
8787

)1e(
Sr
Rb
Sr
Sr
Sr
Sr tλ
86
87
i
86
87
86
87










































i
86
87
86
87
87
86
Sr
Sr
Sr
Sr
Rb
Sr
1ln
λ
1
t
RB-SR DATING
 Based on:
 Needed?
► Rb/Sr elemental ratio
• Traditionally determined via IDMS (accuracy & precision)
► 87Sr/86Sr isotope ratio
• TIMS, MC-ICP-MS, ICP-MS
► (87Sr/86Sr)initial
 Condition?
► System has always been closed with respect to Rb & Sr
 In practice?
► Isochron dating



































i
86
87
86
87
87
86
Sr
Sr
Sr
Sr
Rb
Sr
1ln
λ
1
t
RB-SR ISOCHRON DATING
► Is equation for straight line: y = a + bx
• With y = 87Sr/86Sr and x = 87Rb/86Sr
)1e(
Sr
Rb
Sr
Sr
Sr
Sr tλ
86
87
i
86
87
86
87







isochron
1
1: at the time of the genesis of the rock, all of its
minerals display the same 87Sr/86Sr isotope ratio
RB-SR ISOCHRON DATING
RB-SR ISOCHRON DATING
1
2
3
2: as the rock ages, 87Rb decays into 87Sr 
the Rb concentration decreases & the Sr concentration increases
the 87Sr/86Sr isotope ratio increases
Data points for all minerals remain on one straight line = isochron (3)
RB-SR ISOCHRON DATING
IN PRACTICE
Slope = (et – 1)  t  rock age (t)
Extrapolation  intersection w Y-axis for x = 0  (87Sr/86Sr)i
PROVENANCE DETERMINATION
VIA SR ISOTOPIC ANALYSIS
 Varying geology
 Varying Sr isotopic composition
 Sr isotopic composition, same for:
► Rocks
► Soil
► Vegetation
► Cattle
► ….
Flanders
Wallonia
Ardennes
50 km
Holocene
Pleistocene
Pliocene
Miocene
Oligocene
Eocene
Cretaceous
Jurassic
Triassic
Permian
upper-Carboniferous
lower-Carboniferous
Devonian
Silurian
Cambrian
Quaternary
Tertiary
Mesozoic
Palaeozoic
NATURAL VARIATIONS IN THE ISOTOPIC COMPOSITION OF SR
– PROVENANCE DETERMINATION OF AGRICULTURAL PRODUCTS
Transfer of Sr without
measurable isotopic
fractionation
 Provenancing agricultural products ?
► To detect incorrect indication of geographical origin (fraud)
 Which products?
► Of plant origin:
• Wine: Almeida & Vasconselos, JAAS, 2001, Barbaste et al., JAAS, 2002
• Cider: Garcia-Ruiz et al., ACA, 2007
• Rice: Kawasaki et al., Soil Sci Plant Nutr, 2002
• Ginseng: Choi et al., Food Chem, 2008
• Asparagus: Swoboda et al.,ABC, 2008
• …
► Of animal origin:
• Cheese: Fortunato et al.,JAAS, 2004
• Caviar: Rodushkin et al.,ACA, 2008
• …
NATURAL VARIATIONS IN THE ISOTOPIC COMPOSITION OF SR
– PROVENANCE DETERMINATION OF AGRICULTURAL PRODUCTS
AUTHENTICATION OF KALIX (NE SWEDEN) VENDACE CAVIAR
RODUSHKIN ET AL., ACA, 583, 310, 2007
87Sr/86Sr:
seasonal variation Kalix
< geographical variation
complemented with:
trace element fingerprint
Os isotopic analysis
SR ISOTOPIC ANALYSIS OF FISH OTOLITHS
FOR DISCOVERING FISH MIGRATION PATHS
Otolith or ear bone
 Otoliths or "ear bones" consist of three pairs of small carbonate bodies that are
found in the head of teleost (bony) fish. Otoliths are primarily associated with
balance, orientation and sound detection, and function similarly to incus, malleus
and stapes in the inner ear of mammals
 An otolith's ring structure can provide information about an individual's age,
growth rate, and environment. In some cases, these patterns are a natural record;
in other cases they are induced by man.
Otolith or ear bone
SR ISOTOPIC ANALYSIS OF FISH OTOLITHS
FOR DISCOVERING FISH MIGRATION PATHS
Occurrence of growth rings  Chronological archive

Spatially resolved Sr isotopic analysis via laser ablation MC-ICP-MS

Reveals migration pathways with sub-annual resolution
Fish otolith with growth rings Tree rings
Outridge et al., Environ. Geol., 2002, 42, 891-899
Transfer of Sr without
measurable isotopic
fractionation
NATURAL VARIATIONS IN THE ISOTOPIC COMPOSITION OF SR
– PROVENANCE DETERMINATION OF AGRICULTURAL PRODUCTS
SR ISOTOPIC ANALYSIS FOR
PROVENANCE DETERMINATION OF HUMAN REMAINS
 Enamel
► Formed during early childhood
► 87Sr/86Sr ~ food age 1 – 10
 Dentine
► Continuously renewed
► Faster Sr turnover rate
► 87Sr/86Sr ~ food last years
 Useful info
► Archaeology
► Forensics
SR ISOTOPIC ANALYSIS FOR
PROVENANCE DETERMINATION OF HUMAN REMAINS
 St-Servatius basilica
► Maastricht, Netherlands
► 1600 years of history
► Early christianity in the Maas valley
► Important archaeological excavations
► Analysis of the grave-field population
• Locals and/or immigrants?
 Sr isotopic analysis of tooth tissue & soil (UGent & ETH)
► Acid digestion of samples (open beaker – HNO3 & HCl)
► Isolation of Sr using Sr-spec (Eichrom Technologies)
► Sr isotopic analysis using multi-collector ICP-MS
87
Sr /
86
Sr enameldentine
0,7098
0,7090
0,7100
0,7092
0,7102
0,7094
0,7104
0,7096
0,7106
108-I
108-M
454-I
454-M
71-M
Pandhof population
I: incisor, M: molar
SR ISOTOPIC ANALYSIS FOR
PROVENANCE DETERMINATION OF HUMAN REMAINS
B. Bourdon et al, Rev. Miner. Geochem, 52, 1-19, 2003.
► 238U  206Pb
► 235U  207Pb
► 232Th  208Pb
► 204Pb: not radiogenic
NATURAL VARIATIONS IN
THE ISOTOPIC COMPOSITION OF PB
 Pronounced variation!
► Measurable by TIMS, MC-ICP-MS, single-collector ICP-MS
 Pb in the earth’s crust
► Shows isotopic variation
► 206Pb/207Pb ~ 1.20
 Pb in ores
► Ore formation  separation of Pb from Th & Pb
• Isotopic compostion of Pb “frozen”
► ≠ mines show ≠ Pb isotopic composition:
• Time of ore deposit formation
• U/Pb, Th/Pb ratio in parent material
 Isotope ratio applications ?
► Distinction between crustal Pb & ore-Pb
► Distinction between Pb (ores) of different provenance
PbS ore – galena
NATURAL VARIATIONS IN
THE ISOTOPIC COMPOSITION OF PB
PB – ENVIRONMENTAL POLLUTION
 Pb in the atmosphere
► Geogenic background: crustal “signature”
► Pollution: “ore signature”
►  possibility to calculate relative contributions
2.04
2.05
2.06
2.07
2.08
2.09
2.10
0.825 0.830 0.835 0.840 0.845 0.850 0.855
207
Pb/206
Pb
208
Pb/206
Pb
Source 1
Pb added to gasoline
(anti-knocking agent)
Source 2
Local, geogenic
lead
PB – ENVIRONMENTAL POLLUTION
CALCULATION OF RELATIVE CONTRIBUTIONS
2.04
2.05
2.06
2.07
2.08
2.09
2.10
0.825 0.830 0.835 0.840 0.845 0.850 0.855
207
Pb/206
Pb
208
Pb/206
Pb
Source 1
Pb added to gasoline
(anti-knocking agent)
Source 2
Local, geogenic lead
CASE STUDY – PB POLLUTION IN MARINE SEDIMENTS
NEAR CASEY STATION, ANTARCTICA
Pollution established @ Brown Bay
Townsend and Snape, JAAS, 17, 922-928, 2002.
CASE STUDY – PB POLLUTION IN MARINE SEDIMENTS
NEAR CASEY STATION, ANTARCTICA
 Samples
► Grab samples + core samples
 Sample preparation
► Stored frozen
► Dried at 105oC
► Sieved to <2mm grain size
► Total digestion using concentrated mineral acids, including HF
 Measurement of Pb isotope ratios
► Single-collector sector field ICP-MS
• 1200 scans in ~2 min
• 201Hg monitored to correct for potential isobaric interference on 204Pb
• Correction for mass discrimination corrected using NIST SRM 981
– Isotopic reference material
– Bracketing approach
Townsend and Snape, JAAS, 17, 922-928, 2002.
CASE STUDY – PB POLLUTION IN MARINE SEDIMENTS
NEAR CASEY STATION, ANTARCTICA
Broken Hill mining area Pb
= potential source of contamination
Low Pb-level sediments
‘local’ Pb
Mixing line
Townsend and Snape, JAAS, 17, 922-928, 2002.
CASE STUDY – PB POLLUTION IN MARINE SEDIMENTS
NEAR CASEY STATION, ANTARCTICA
Mixing line
The higher the Pb concentration, the closer the 208Pb/204Pb ratio to the Broken Hill value
Straight lines are preferred  use 1/Pb instead
Background Pb
Mixing line
Townsend and Snape, JAAS, 17, 922-928, 2002.
CASE STUDY – PB POLLUTION IN MARINE SEDIMENTS
NEAR CASEY STATION, ANTARCTICA
PB – ENVIRONMENTAL POLLUTION
MORE THAN TWO SOURCES…
2.04
2.05
2.06
2.07
2.08
2.09
2.10
0.825 0.830 0.835 0.840 0.845 0.850 0.855
207
Pb/206
Pb
208
Pb/206
Pb
Source 1
Source 2
Source 1
F. Vanhaecke et al, JAAS, 24, 863-886, 2009.
NATURAL VARIATION
APPLICATIONS BASED ON ISOTOPE
FRACTIONATION
11B/10B AS A PALEO PH SEAWATER PROXY
 B in seawater:
► Present as B(OH)3 & B(OH)4
- / distribution dependent on pH
► 11B/10B isotope ratio in the past?  foraminifera & corals
pH pH
Concentration (µmol/kg) 11B
sea water
11B/10B AS A PALEO PH SEAWATER PROXY
 In seawater:
B(OH)3 + H2O  B(OH)4
- + H+
isotopically
heavier
isotopically
lighter
B(OH)4
- taken up
without isotopic fractionation
in corals & foraminifera
Foraminifera
living or fossil
eukaryotic monocellular
organisms with CaCO3 skeleton
pH of seawater as a
function(time)
RELEVANCE OF PH OF SEAWATER ?
 Determined by CO2 concentration in the atmosphere
► Information on CO2 level over geological times
► Is the current increase in CO2 level exceptional ?
CO2
H2CO3
RELEVANCE OF PH OF SEAWATER ?
?
S ISOTOPIC ANALYSIS FOR TRACING DOWN COUNTERFEIT DRUGS
R. CLOUGH ET AL., ANAL. CHEM., 78, 6126, 2006.
 Counterfeit drugs
► violation of intellectual property laws
► inappropriate quantities of active ingredients
► may contain ingredients that are not on the label (purity)
► often inaccurate, incorrect or fake packaging & labeling
 “Money making” drugs
S ISOTOPIC ANALYSIS FOR TRACING DOWN COUNTERFEIT DRUGS
R. CLOUGH ET AL., ANAL. CHEM., 78, 6126, 2006.
 S isotopic analysis in viagra using LA-MC-ICP-MS
► Higher mass resolution
STUDY OF ISOTOPE FRACTIONATION
IN THE CONTEXT OF BIOMEDICAL APPLICATIONS
As Fe proceeds through the food chain,
(56Fe/54Fe) is reduced by approx 1 ‰ with
each trophic level.
Thorough investigation should provide
information on uptake & transfer of Fe.
Walczyk and von Blanckenburg, Science, 295, 2065- 2066, 2002.
UPTAKE OF FE IN THE SMALL INTESTINE
Fe isotopic analysis  tool for efficiency of (non-heme) iron absorption
Tool for diagosing hereditary chromatosis
Krayenbuehl et al, Blood, 105, 3812-3816, 2005.
NATURAL VARIATION
APPLICATIONS BASED ON EXTINCT
RADIONUCLIDES
THE 182HF-182W CHRONOMETER
S.B. JACOBSEN, EPSL, 33, 531-570 2005.
Very short compared to
age of solar system
Extinct
radionuclide
c
W isotopic analysis
TIMS: hampered by hihgh IE(W) = 7,98 eV
Straightforward with MC-ICP-MS
c
THE 182HF-182W CHRONOMETER
S.B. JACOBSEN, EPSL, 33, 531-570, 2005.
 Formation of a planet ?
► Accretion
• Growth of an object by attracting more matter (gravity)
► Differentiation
• Core formation
Iron core (heavy)
Crust (light)
Hf = lithophile

prefers crust
W = siderophile

prefers core
THE 182HF-182W CHRONOMETER
S.B. JACOBSEN, EPSL, 33, 531-570 2005
 Effect of planetary differentiation?
► Situation 1: Hf & W only separated after extinction of 182Hf
• Hf/W ratio ~ chondritic meteorites (unfractionated reservoir)
► Situation 2: Hf & W were separated while 182Hf was still around
• High Hf/W ratio in crust  higher enrichment in 182W
 182Hf-182W chronometer
► Timing of planetary differentiation
Increase in
182W/183W
In silicate fraction
THE 182HF-182W CHRONOMETER
S.B. JACOBSEN, EPSL, 33, 531-570 2005
THE END …