Accurate mass analysis of hydraulic fracturing waters: Identification of polyethylene glycol surfactants by LC/Q-TOF-MS
Agilent Technologies, Inc.
June 2015
May 21, 2015 Confidentiality Label 1
W h a t i s H y d r a u l i c F r a c t u r i n g ? W h y i s i t i m p o r t a n t ?
• Thermogenic Methane
• Natural Gas & Oil
• 45,000 Wells in US
• 7500 Wells in Colorado
• Natural Gas Prices Down
• US Energy Reserves UP
• High Water Use per well
106 Gallons
• Greenhouse Gases
• Groundwater Contam
• Aesthetics
• Risks Shallow Aquifers
• Methane and HC
• Fracking Fluids
• Metals
• Radionuclides
• Salts
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S h a l e G a s F i e l d s L o w e r 4 8 S t a t e s
Hydraulic Fracturing Production Activity Price per Wellhead
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Vengosh et al. 2014 ES&T
Hydraulic Fracturing for Natural Gas Contamination Risks
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Hydraulic Fracturing for Natural Gas Potential Risks
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LC/QTOF-MS with High Resolution and Accurate Mass In Search of “Tracers” of “Fracking” Contaminates
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• Six flowback samples from
Colorado
• Dilute 1/10, filter through
PFTE 0.1 micron
• Use slow gradient with C-8
column, 3.5 micron, 0.1%
Formic acid/ACN gradient
• High Res Q-TOF analysis
with accurate mass
– 1290 Agilent UHPLC
– 6540 Agilent Q/TOF
– 1 ppm Mass Accuracy
– 25,000 Resolving Power
Samples and Prep
Work performed by Dr. Michael Thurman, University of Colorado, Boulder
Total Ion Chromatogram Production flow-back water from Niobrara Formation
24 June 2015
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Hydrophilic Series
Hydrophobic Series
• Series of Peaks early and late in the chromatogram
• A Hydrophilic Series and a Hydrophobic series
• Masses Differ by 44 mass units suggesting CH2-CH2-O structure for both
Fracturing Fluid Composition What is injected into the well?
24 June 2015
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Proprietary “mixture” containing:
• Water, sand, surfactants, biocides, solvents, distillates, simple
alcohols and glycols, recycled water
Ingredient disclosure required in Colorado
Glycols -CH2-CH2-O = 44 u
Fracturing Fluid Composition Mass Difference among HPI and HPO Series (Ethoxylates?)
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Calculating Kendrick Mass Scaling Factor for [CH2-CH2-O]
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KM Scaling Factor = Isobaric Mass of CH2-CH2-O /
Accurate mass of CH2-CH2-O
KMSF = 44.0000/ 44.0265
KMSF = 0.999404559
Calculating Kendrick Mass Scaling Factor for [CH2-CH2-O]
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KM = Measured Accurate mass x KMSC
KM Defect = Nominal KM-Exact KM
Why it works: adding exactly 44.0000 mass units
to each new polymeric species, i.e. EO-5 to EO-6, etc.;
therefore, mass defect remains the same. Multiplication of
0.999404559 makes this correction for all related
compounds.
Applying the Kendrick Mass Defect to Measured Masses in HPI-Series
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Time Measured Mass Kendrick Putative Identification Exact Mass Error
(Min) (m/z) Mass (m/z) (ppm)
3.5 173.0784 172.975 PEG-EO3 Na Adduct 173.0784 0.0
4.2 217.1042 216.975 PEG-EO4 Na Adduct 217.1046 2.0
5.4 261.1304 260.975 PEG-EO5 Na Adduct 261.1309 2.0
7.3 305.1569 304.975 PEG-EO6 Na Adduct 305.1571 0.7
9.5 349.1833 348.975 PEG-EO7 Na Adduct 349.1833 0.0
10.2 393.2092 392.975 PEG-EO8 Na Adduct 393.2095 0.8
10.7 432.2802 432.023 PEG-EO9 NH4 Adduct 432.2803 0.2
11.0 476.3066 476.023 PEG-EO10 NH4 Adduct 476.3065 0.2
11.3 520.3324 520.023 PEG-EO11 NH4 Adduct 520.3328 0.8
11.5 564.3585 564.022 PEG-EO12 NH4 Adduct 564.3590 0.9
11.7 608.3856 608.023 PEG-EO13 NH4 Adduct 608.3852 0.7
11.9 652.4113 652.023 PEG-EO14 NH4 Adduct 652.4114 0.2
• Formula Generation from m/z 173.0784
• C6H14O4-Na+ ------Chem Spider Search
• Identification of PEGs
• Next test Model with MS/MS, PEG EO-6 and EO-12
MS/MS of m/z 283 (1) and MS/MS of EO-12 at m/z 564 (2) May be the EO-6 H+
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44.01267
44.01254
44.01261
44.01257
44.01256
44.01263 44.01255 CH2=CHOH
18.0110
MH+
MNH4+
MNa+
1
2
MS/MS of m/z 283 and MS/MS of EO-12 at m/z 564 May be the EO-6 H+
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Two Series of Fragmentations
• H20 and CH2=CHOH to 3 diagnostic ions
• CH2=CHOH and H20 to 3 diagnostic ions
89, 133, 177 (Ferrer et al. 2003)
O OH
C4H9O2+
Exact Mass: 89.0597
O O
OH
C6H13O3+
Exact Mass: 133.0859
O O
O
OH
C8H17O4+
Exact Mass: 177.1121
O
HO
HO
O O
O
OO
HO
Chromatogram of PEG-400 Standard (Mixture)
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EO-6
EO-6 Na+
EO-6 H+
283.1751
564.3585 EO-12
Na+ H+
NH4+
PEG-EO7
PEG-EO8
PEG-EO9
NH4+
NH4+
H+
H+
Na+
Na+
OH(CH2CH2O)8H
H
C16H35O9+
Exact Mass: 371.2276
OH(CH2CH2O)7H
H
C14H31O8+
Exact Mass: 327.2013
OH(CH2CH2O)9H
H
C18H39O10+
Exact Mass: 415.2538
Proposed Crown Ether Structure Ammonium Adduct Formation
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O
O
O
O
O
O
O
O
OHN
H
H
HH
OH
Ionic Radii
Na+ =0.102 nm, H3O+ = 0.143 nm
K + = 0.138, NH4+ = 0.145 nm
Percent Adduct Type
EO-8 PEG H+ Na+ NH4+
% % %
EO-4 4 96
EO-5 15 85
EO-6 33 66
EO-7 60 40
EO-8 40 20 40EO-9 20 20 60
EO-10 15 15 70
EO-11 6 14 80
EO-12 5 15 80
EO-13 6 14 80
EO-14 6 14 80
PEG H+ Na+ NH4+% % %
EO-4 1 99
EO-5 8 92
EO-6 20 80
EO-7 40 60
EO-8 33 33 33EO-9 20 30 50
EO-10 10 25 65
EO-11 5 25 70
EO-12 5 25 70
EO-13 5 25 70
EO-14 5 25 70
NH4+ Na+
Density Functional Theory DFT Calculations by Jens Blotvogel, CSU
Table S3: Total free energies, binding constants, and atomic distances for the PEG-EO9
ammonium complex as a function of the number of interacting oxygen atoms calculated
at the IEFPCM/B3LYP/6-311G(d,p) level of theory.
No. of
interacting O
Total Free
Energy
(hartree)
Binding
Constant
log K
Min. H-O
Distance
(Å)
Avg. H-O
Distance
(Å)
Min. N-O
Distance
(Å)
Avg. N-O
Distance
(Å)
6 -1517.854737 4.5 1.86 3.44 2.85 4.18
7 -1517.856880 5.5 1.86 2.99 2.86 3.64
8 -1517.861084 7.4 1.90 2.73 2.92 3.48
9 -1517.862942 8.3 1.84 2.60 2.87 3.31
10 -1517.866147 9.7 1.84 2.44 2.87 3.14
Table S4: Total free energies, binding constants, and atomic distances for the PEG-EO9
sodium complex as a function of the number of interacting oxygen atoms calculated at
the IEFPCM/B3LYP/6-311G(d,p) level of theory.
No. of
interacting O Total Free Energy
(hartree) Binding
Constant log K Min. Na-O
Distance (Å) Avg. Na-O
Distance (Å)
6 -1623.106201 2.6 2.44 4.03
7 -1623.109024 3.9 2.46 3.54
8 -1623.109559 4.1 2.49 3.22
9 -1623.111726 5.1 2.49 3.16
10 -1623.117648 7.9 2.44 3.00
Table S5: Total free energies and binding constants for the PEG-cation complexes
calculated at the IEFPCM/B3LYP/6-311G(d,p) level of theory.
Na+ NH4
+ Δ log K
(NH4+ - Na
+)
Total Free
Energy
(hartree)
Binding
Constant log
K
Total Free
Energy
(hartree)
Binding
Constant log K
PEG EO9 -1623.117648 7.9 -
1517.866147 9.7 1.8
PEG EO8 -1469.300690 10.0 -
1364.047481 11.1 1.1
PEG EO7 -1315.483483 12.2 -
1210.227166 11.8 -0.4
This result explains why we see the PEG prefer NH4+ ion over Na+ at EO-8.
60X
NH4
Free Energy and Binding Constants
Changes in Adduct Formation
EO-20 changes to NH4+ and NH4+
OO
O
OO
O
OOO
HO
OO
O
OO
O
OO
HO
NH H
H
H
N HH
H
H
H3O+ = 0.143 nm
H+
Hydrophobic Series
Total Ion Chromatogram - Production Water
• Late Series of peaks in the chromatogram
• Masses Differ by 44 mass units suggesting CH2-CH2-O structure
• Elution reverses, more EOs the shorter the retention time
26.05 820.5996 820.111 C-12 EO-14 NH4
26.28 776.5740 776.112 C-12 EO-13 NH4 44.0256
26.49 732.5475 732.111 C-12 EO-12 NH4 44.0265
26.71 688.5215 688.112 C-12 EO-11 NH4 44.0260
26.93 644.4952 644.111 C-12 EO-10 NH4 44.0263
27.16 600.4686 600.111 C-12 EO-9 NH4 44.0266
27.40 556.4422 556.111 C-12 EO-8 NH4 44.0264
27.65 512.4160 512.111 C-12 EO-7 NH4 44.0262
27.89 468.3898 468.111 C-12 EO-6 NH4 44.0262
• Kendrick Mass Defect all equal, EO accurate mass
• Formula for m/z 468.3898 is C24H54NO7
• Chem Spider matches a C-12 ethoxylate
• MS/MS is next
MS/MS of m/z 468.3896 C-12 EO-6 NH4
468.3896
-17.0010
NH3
-168.1883
-18.0101
-44.0262
Na+ 21.9821
HO
(CH 2CH 2O )6H
N H 3C 24H 54N O 7+
Exact M ass: 468.3895
C -12 EO 6
C12H24
Exact Mass: 168.1878
H+H+
H+NH4+
H+Na+
Na+Na+
NH4+NH4
+ NH4
+Na+
PEG EO17
Mass Spectrum for doubly charged PEG EO17 with mixed double adducts of Na+, NH4+,
and H+ for sample SF-1. The singly charged PEG EO17 also formed at a lesser
concentration with adducts of H+, Na+, and NH4+ (data not shown). The doubly charged
species shown here were the major ions found in the mass spectrum.
Mass Spectrum for doubly charged PEG EO17
SF-1
107
107
21 PEGs
30 PEGs
20 PEGs
GF-1
SF-2 107 EO-9
EO-9
EO-9
EO-21
Bimodal PEGs
Figure S3. Frac-t-Gram for PEG surfactants in three flowback samples.
Conclusions
PEG Composition
1. PEGs (in all 3 flowback samples)
2. Alkyl-EOs present in (2) flowback samples
3. Produced Water has PEGs
Kendrick Mass Defect
1. KMD works to find related EO’s
2. KMD finds multiply charged species
3. KMD finds mixed adducts
Acknowledgments
Tom Evans of Protreat Technologies, Denver, CO, for
Flowback Samples
Joe Weitzel and Jerry Zweigenbaum of Agilent
Technologies, Inc. for LC/QTOF-MS support
Acknowledgments