SUPPORTING INFORMATION
Stable isotope analysis of intact oxyanions using electrospray
Quadrupole-Orbitrap mass spectrometry
Cajetan Neubauer
1,*,‡
, Antoine Crémière
1
, Xingchen T. Wang
1
, Nivedita Thiagarajan
1
, Alex L. Sessions
1
,
Jess F. Adkins
1
, Nathan F. Dalleska
2
, Alexandra V. Turchyn
3
, Josephine A. Clegg
3
, Annie Moradian
4
,
Michael J. Sweredoski
4
, Spiros D. Garbis
4
, John M. Eiler
1
1. Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA
91125, USA.
2. Environmental Analysis Center, California Institute of Technology, Pasadena, CA 91125, USA
3. Department of Earth Sciences, University of Cambridge, Cambridge, CB2 3EQ, United Kingdom.
4. Proteome Exploration Laboratory, California Institute of Technology, Pasadena, CA 91125, USA.
* Corresponding author:
123caj@gmail.com
‡ Present address: Hanse-Wissenschaftskolleg, Lehmkuhlenbusch 4, 22753 Delmenhorst, Germany
Table of contents:
●
Supplemental methods:
Bulk isotopic composition
●
Table S1.
Existing methods for isotopic analysis of sulfate and nitrate
●
Table S2.
Description of the sulfate and nitrate materials used in this study, including their
isotopic composition as determined by IRMS
●
References
for information in Table S1 and Table S2
S-1
Supplemental methods
Bulk isotopic composition.
The isotopic compositions of in-house reference standards of sulfate salts
were obtained by conventional IRMS methods. Sulfur-34 isotope measurements were done on an
elemental analyzer-isotope ratio mass spectrometer (EA-IRMS) using the same Na
2
SO
4
stock solutions
used for ESMS measurements. The solution was pipetted directly into tin capsules and dried overnight at
70°C. Results were normalized to international reference materials IAEA-S-1, IAEA-S-2, and IAEA-S-3
with δ
34
S values taken from Brand et al.
1
as well as in-house Na
2
SO
4
and seawater solutions. The
precisions for δ
34
S
SO4
measurements are better than 0.2 ‰.
Oxygen-18 isotope measurements were analyzed on a thermal-conversion (TC) EA-IRMS. Sulfate in
solution was converted to barite through precipitation with BaCl
2
. The barite was cleaned using 6M HCl,
to dissolve any barium carbonate co-precipitate, and then rinsed three times with deionized water and
dried in the oven overnight. Barite was weighed into silver capsules and pyrolyzed in a TC/EA, and
measured via continuous helium flow on a Delta V mass spectrometer. Samples were run for δ
18
O
SO4
ten
times and the average and standard deviation presented. These samples were bracketed with NBS-127
(δ
18
O
SO4
= 8.6 ‰
VSMOW
), whi
ch was used to correct for drift over the course of the run. The isotopic
composition of sulfate and nitrate materials determined by conventional isotope-ratio analysis are
summarized in Table S2.
S-2
Supplemental tables
Table S1.
Existing methods for isotopic analysis of sulfate and nitrate
Method*
Conversion and
Analyte
Isotope
Ratio
Precision (‰; 2sd)
Sensitivity
Throughput
(samples/day)
Reference
MC-ICP-MS
Na
2
SO
4
δ
34
S, Δ
33
S
δ
34
S: 0.08-0.15;
Δ
33
S: 0.1-0.3
> 5 nmol sulfur,
typically 20 nmol
< 20
Paris et al. (2013)
2
dual-inlet IRMS
Ag
2
S -> SF
6
δ
34
S, Δ
33
S,
Δ
36
S
δ
34
S: ~0.2,
Δ
33
S: ~0.02
10 μmol
< 10
Hulston and Thode
(1965)
3
EA-IRMS
Sulfate ->SO
2
δ
34
S
> 0.05
> 0.1 μmol sulfur
< 60
Thode et al. (1961)
4
IRMS
Sulfate ->O
2
δ
18
O, Δ
17
O
δ
18
O: 1.6, ∆
17
O: 0.1 (2 for
smaller samples)
> 17 μmol sulfur
> 12
Bao and Thiemens (2000)
5
TC/EA-IRMS
Sulfate ->CO
2
or
CO
δ
18
O
δ
18
O: 0.1-0.3
0.5 μmol
< 40
Boschetti & Iacumin
(2005)
6
GB-IRMS
Nitrate -> N
2
O
(bacterial/chemical
conversion)
δ
15
N, δ
18
O,
Δ
17
O
δ
15
N: 0.2; δ
18
O: 0.3; ∆
17
O:
0.2-0.5
> 2 nmol nitrate,
typically 5-20
nmol
< 120
Sigman et al. (2001)
7
,
Kaiser et al. (2007)
8
,
Weigand et al. (2016)
9
TC/EA-IRMS
Nitrate -> N
2
, O
2
δ
15
N, δ
18
O,
Δ
17
O
δ
15
N: 0.2; δ
18
O: 0.3, Δ
17
O:
1.0
>1 μmol nitrate
< 60
Michalski et al. (2002)
10
,
Böttcher et al (1990)
11
ESMS
Na
2
SO
4
δ
34
S, δ
33
S,
δ
36
S, δ
18
O,
Δ
34
S
18
O
δ
34
S: <2, δ
18
O: <2
< 1 nmol sulfate
(data acquisition)
~10 (manual
sample changing)
This study
ESMS
KNO
3
δ
15
N, δ
18
O,
δ
17
O
δ
15
N: <2, δ
18
O: <2
< 1 nmol nitrate
(data acquisition)
~ 10 (manual
sample changing)
This study
*
EA: elemental analyzer, ICP: inductively coupled plasma, IRMS: isotope-ratio mass spectrometry, MC:
multi-collector, TC: thermal-conversion, GB: gas bench
S-3
Table S2.
Description of the sulfate and nitrate materials used in this study, including their isotopic
composition as determined by IRMS.
Name
Provider
Origin
δ
18
O (‰
VSMOW
; SD)
δ
34
S (‰
VCDT
; SD)
Purity and comments
Antarctica
G. Rossman, Caltech
McMurdo Station,
Antarctica
+8.73±0.82(n=10)
+21.44 ±0.15 (n=5)
likely anhydrous; obtained as
a powder
Cedar Lake
Saltex, Tx (Cooper
Natural)
Cedar Lake, Texas, USA
+12.45±0.44 (n=10)
+10.92±0.2 (n=2)
99.8%; 0.01% water
Chaplin
Airborne Industrial
Minerals
Chaplin, Saskatchewan,
Canada
+11.54±1.14 (n=9)
+3.15±0.2 (n=2)
99.57%; 0.15% MgSO
4
;
0.013% water
Laguna del Rey
Peñoles
Laguna del Rey,
Coahuila, Mexico
+12.92±0.69 (n=9)
+13.91±0.2 (n=2)
99.90%
Mexico
Macron, 8024-04, Batch
0000177887
Made in Mexico
+8.24±0.88 (n=10)
-0.97±0.2 (n=2)
99.20%
Rio Tiron
Crimidesa,
Lot #19-0579
Minera Rio Tiron,
Burgos, Spain
+13.97±0.69 (n=10)
+12.61±0.2 (n=2)
99.8%; 0.01% water;
Soda Lake
G Rossman, Caltech
Soda Lake, Carrizo Plain,
San Luis Obispo Co.,
California, USA
+11.14±0.57 (n=9)
-9.76±0.09 (n=5)
Thénardite; likely anhydrous;
rocks were ground into a
powder
Synthetic India
Sigma Aldrich,
239313-500G
Lot # SLBR3461V
synthetic inorganic
(manufactured in India)
+11.86±0.33 (n=10)
+1.04±0.2 (n=2)
99.90%
Trona
Searles Valley Minerals
Trona, California, USA
+19.76±0.64 (n=10)
+14.69±0.2 (n=2)
99.5%; 0.10% Na
2
CO
3
, 0.34%
NaCl
δ
18
O (‰
VSMOW
; SD),
δ
17
O (‰
VSMOW
; SD)
δ
15
N (‰
air N2
; 2SD)
USGS32
Reston Stable Isotope
Laboratory – USGS
(Reston, Virginia, USA)
USGS32 is a dried
potassium nitrate salt,
prepared by J. K. Böhlke
in 1992 via dissolving and
recrystallizing a mixture
of normal reagent salt and
15
N-enriched salt.
+25.55±0.2;
13.01±0.35
+180 exactly
Böhlke et al. performed
18
O
analysis using a TC/EA by
on-line reduction with carbon.
IRMS of
15
N/
14
N was
performed after
combustion/reduction to
N
2
.
12,13
δ
17
O provided by Andrew
Schauer, Univ. Washington.
USGS34 and USGS35 were
used to calibrate δ
17
O using
the bacterial denitrifier
method and thermal
decomposition.
USGS34
Reston Stable Isotope
Laboratory – USGS
(Reston, Virginia, USA)
Prepared by equilibrating
nitric acid with δ
18
O
depleted Antarctic
snow-melt water and
subsequent neutralization
with KOH
-27.84±0.3,
-14.55
–1.8±0.1
Prepared and characterized
similar to USGS32 by Böhlke
et al.
10
17
O was measured by
off-line decomposition to O
2
.
S-4
References
(1)
Brand, W. A.; Coplen, T. B.; Vogl, J.; Rosner, M.; Prohaska, T. Assessment of International Reference
Materials for Isotope-Ratio Analysis (IUPAC Technical Report).
Pure and Applied Chemistry
2014
,
86
(3),
425–467.
(2)
Paris, G.; Sessions, A. L.; Subhas, A. V.; Adkins, J. F. MC-ICP-MS Measurement of δ
34
S and ∆
33
S in Small
Amounts of Dissolved Sulfate.
Chemical Geology
. 2013, pp 50–61.
(3)
Hulston, J. R.; Thode, H. G. Variations in the S
33
, S
34
, and S
36
Contents of Meteorites and Their Relation to
Chemical and Nuclear Effects.
Journal of Geophysical Research
. 1965, pp 3475–3484.
(4)
Thode, H. G.; Monster, J.; Dunford, H. B. Sulphur Isotope Geochemistry.
Geochimica et Cosmochimica
Acta
. 1961, pp 159–174.
(5)
Bao, H.; Thiemens, M. H. Generation of O
2
from BaSO
4
Using a CO
2
−Laser Fluorination System for
Simultaneous Analysis of δ
18
O and δ
17
O.
Anal. Chem.
2000
,
72
(17), 4029–4032.
(6)
Boschetti, T.; Iacumin, P. Continuous
-
flow δ
18
O Measurements: New Approach to Standardization,
High
-
temperature Thermodynamic and Sulfate Analysis.
Rapid Communications in Mass Spectrometry
.
2005, pp 3007–3014.
(7)
Sigman, D. M.; Casciotti, K. L.; Andreani, M.; Barford, C.; Galanter, M.; Böhlke, J. K. A Bacterial Method
for the Nitrogen Isotopic Analysis of Nitrate in Seawater and Freshwater.
Anal. Chem.
2001
,
73
(17),
4145–4153.
(8)
Kaiser, J.; Hastings, M. G.; Houlton, B. Z.; Röckmann, T.; Sigman, D. M. Triple Oxygen Isotope Analysis of
Nitrate Using the Denitrifier Method and Thermal Decomposition of N
2
O.
Anal. Chem.
2007
,
79
(2),
599–607.
(9)
Weigand, M. A.; Foriel, J.; Barnett, B.; Oleynik, S.; Sigman, D. M. Updates to Instrumentation and Protocols
for Isotopic Analysis of Nitrate by the Denitrifier Method.
Rapid Commun. Mass Spectrom.
2016
,
30
(12),
1365–1383.
(10)
Michalski, G.; Savarino, J.; Böhlke, J. K.; Thiemens, M. Determination of the Total Oxygen Isotopic
Composition of Nitrate and the Calibration of a Δ
17
Ο Nitrate Reference Material.
Anal. Chem.
2002
,
74
(19),
4989–4993.
(11)
Böttcher, J.; Strebel, O.; Voerkelius, S.; Schmidt, H.-L. Using Isotope Fractionation of Nitrate-Nitrogen and
Nitrate-Oxygen for Evaluation of Microbial Denitrification in a Sandy Aquifer.
J. Hydrol.
1990
,
114
(3),
413–424.
(12)
Böhlke, J. K.; Gwinn, C. J.; Coplen, T. B. New Reference Materials for Nitrogen-Isotope-Ratio
Measurements.
Geostandards Newslett.: J. Geostandards Geoanalysis
1993
,
17
(1), 159–164.
(13)
Böhlke, J. K.; Coplen, T. B.
Interlaboratory Comparison of Reference Materials for Nitrogen-Isotope-Ratio
Measurements
; IAEA-TECDOC-825; IAEA, 1995.
S-5