GPC/SEC with Mass Spectrometry
Detection: A Winning Team?
Peter Kilz, PSS GmbH, 55023 Mainz, Germany
[email protected]
1. Matching up Two Worlds
2. How To: Hyphenating GPC/SEC with MS
3. GPC-MS: Insight Into Polymer Reactions
4. Summary
International Symposium GPC/SEC & Related techniques, Amsterdam, September 28, 2016
Acknowledgement
Norbert Hirschberger,
PSS Polymer Standards Service GmbH
Prof. Christopher Barner-Kowollik
Queensland University of Technology, Australia
Dr. Till Gründling
BASF SE, Germany
International Symposium GPC/SEC & Related techniques, Amsterdam, September 28, 2016
Matching up Two Worlds
Macromolecules
all:
high molar mass
most: solid
vs.
Mass Spectrometry
gas phase separation
of ionized species
in high vacuum
not a simple start …
International Symposium GPC/SEC & Related techniques, Amsterdam, September 28, 2016
Page 3
Matching up Two Worlds
GPC/SEC Systems
vs.
Mass Spectrometers
not simple either …
International Symposium GPC/SEC & Related techniques, Amsterdam, September 28, 2016
Page 4
Matching up Two Worlds
GPC/SEC
Advantages and Limitations of
Mass Spectrometry
+ standard technique
+ applicable to all macromolecules
+ can separate mixtures
+ non-specific detection
o separates by size
- low resolution
- unspecific (in general)
- difficult to detect traces
- co-eluting species
+ software for specific data treatment
- limited by high price
- exotic with polymers
- difficult spectra of mixtures
- risk of ion suppression
+ direct molar mass measurement
+ high resolution
+ high specificity/identification
+ high sensitivity (very low LOD)
+ independent separation in MS
- no specific software for polymers
Good balance of pros/cons
hyphenation has potential
International Symposium GPC/SEC & Related techniques, Amsterdam, September 28, 2016
Page 5
How To Hyphenate
fractions from GPC/SEC separation
MS
MS control +
requires powerful PC,
creates large data sets
Major Problem:
- generate gas phase species from charged solid analytes
International Symposium GPC/SEC & Related techniques, Amsterdam, September 28, 2016
Page 6
How To Hyphenate
MS Instrument:
- controlled by instrument specific software
- MS spectra saved in MS software
- MS data file used by PSS WinGPC
Split flow RI-MS (~90/10)
Add salt for soft ionization
LC/GPC instrument:
- controlled by PSS WinGPC
- concentration detector data for quantitative results
- MS data merged to WinGPC database
7
International Symposium GPC/SEC & Related techniques, Amsterdam, September 28, 2016
How To Hyphenate
45
40
?
?
30
25
?
?
20
15
PSS WinGPC Unity, Build 3523, LAB-SW1, Instance #1
RI Signal [mV]
35
10
5
5.0
7.5
10.0
12.5
15.0
17.5
20.0
22.5
25.0
27.5
30.0
Elution volume [ml]
column
visco
LS
RI
MS
Mw
Rg, g
structure
c
-
Mn
endgroup,
repeat units,
by-products,
etc., …
Information content:
Primary:
Secondary:
[η]
M, g‘
structure
Understanding local polydispersity:
measure Mw (LS) / Mn (MS)
International Symposium GPC/SEC & Related techniques, Amsterdam, September 28, 2016
Information Content
GPC-MS combines benefits of both
GPC (separation) and MS (information content)
Qualitative information
Quantitative information
(Status quo ante)
(Current state-of-the-art)
Chemical structure of the macromolecules
Molar mass distribution & averages
(repeating units, functional endgroups,
backbone structure)
Concentration of individual macromolecular
species in mixtures
Band-broadening correction
• Obtained from MS detector alone
• Molecular formula from hires MS (FT/ICR
or Orbitrap)
• Increased information content from
MS/MS
• Multiple charging allows M < 50.000 Da
to be analyzed
• Obtained from concentration detector with
internal calibration by MS
Requires sophisticated data treatment
Convolution of EIC’s to fit RI mass
International Symposium GPC/SEC & Related techniques, Amsterdam, September 28, 2016
Information Content
WinGPC supports users with MS relevant information:
- charge-state correction
- isotope correction
- spectral deconvolution
- reconstitution of
concentration signal
Data analysis results:
- chain length
- endgroup mass
- repeat unit masses
- unassigned species
- absolute M and MWD
International Symposium GPC/SEC & Related techniques, Amsterdam, September 28, 2016
Page 10
Information Content
O
1200
GPC:
- endgroups co-elute
MS:
- can separate/identify
- reveals sample mixture0
1250
1300
1350
1400
1450
SEC-calibration, relative
abundance of oligomers
1500
1564.92
1575.50
1375.42
1364.83
Br
n
Binary mixture of two
functional polymers
1314.75
1325.25
OMe
1275.25
O
18
retention time /min
1550
20
22
24
monomer units, functional
endgroups, backbone
structure
1600
1664.92
1675.58
16
1615.00
1625.58
14
1514.75
1525.50
12
1464.83
1475.50
10
H
n
Mass Spectrum
MeO
RI signal
OMe
1425.42
H
?
1414.75
O
?
Total mass concentration
of polymer
fraction
Investigtion of binary
polymer blend
1650
1700
m/z
Retention time, tR
Peak dispersion, σ, τ
Area, A
2
4
6
8
10
12
14
retention time /min
International Symposium GPC/SEC & Related techniques, Amsterdam, September 28, 2016
16
18
20
22
1750
1800
Single Oligomer
Profiles (SOP)
= Extracted Ion
Chromatogram
Verification of Data Processing
Comparison with NIST SRM2881:
• Absolute molecular weight polystyrene standard
• MWD determined solely by MALDI (internal mass bias correction)
+
Ag
Bu
Excellent
H
n
agreement SRM data with GPC-ESI-MS results
Perfect MWD overlay corroborates accuracy of methodologies
Independent verification of WinGPC MS data treatment (implementation)
International Symposium GPC/SEC & Related techniques, Amsterdam, September 28, 2016
Verification of Data Processing
MS generated calibration
3
VG /cm3
7.5
5
4
charge
6 state
GPC-MS with MaxEnt
corrects for peak broadening
– Only slight effects due to good column
resolution
– Important for oligomer analysis
7.0
0.03
6.5
Results based on
Manufacturer
75
125 175
repeat
unit
(n)
repeat unit (DP)
DPw
102.00
NMR (bulk)
DPn
99.00
PDI
0.02
w(n)
6.0
25
0.01
1.03
94.5 ±1%
GPCwith RI/MS (/w
MaxEnt correction)
96.66
(-5%)
93.44
(-6%)
1.035
GPC with MS
calibration
97.23
(-5%)
93.60
(-6%)
1.039
0.00
0
50
100
150
repeat
repeatunit
unit(DP)
(n)
200
Gruendling et al., Anal. Chem. 2008, 80, 6915-6927.
International Symposium GPC/SEC & Related techniques, Amsterdam, September 28, 2016
MS Data Analysis with
WinGPC Software
What Can We Learn from GPC with MS Detection
Raw Data View of Unknown
Automatic identification
- poly(methyl acrylate)
- 2 endgroups
propyl (43), butyl (57)
Observations:
- simple charge pattern
- good mass resolution
- 2 main distributions
same repeat units
∆m/e: 86.089 amu
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MS Data Analysis with
WinGPC Software
What Can We Learn from GPC with MS Detection
Raw Data View of PMA
Automatic assignment
by WinGPC software:
- charge state
- chain length
- endgroup masses
- repeat unit masses
Polymeric structure
BUT also
- many non-assigned
irregular chains
PSS - WatersSymposium
International
Meeting, July
GPC/SEC
2013 & Related techniques, Amsterdam,
www.pss-polymer.com
September 28, 2016
Page 15
MS Data Analysis with
WinGPC Software
Analysis of Poly(methyl acrylate) by GPC-MS
Molar Mass Overview of Species by MS
Calibration reveals:
- GPC separation of regular
chains
- no separation if irregular
species
MS reveals:
- co-elution of species
- sample component does not
elute in SEC mode
However:
Still absolute M and MWD
PSS - WatersSymposium
International
Meeting, July
GPC/SEC
2013 & Related techniques, Amsterdam,
www.pss-polymer.com
September 28, 2016
Page 16
MS Data Analysis with
WinGPC Software
Analysis of Poly(methyl acrylate) by GPC-MS
Sample characteristics with correct and incorrect assignment
regular
Mn [Da] 1614
Mw [Da] 2105
PDI
1.30
irregular
7529
7537
1.001
MWD overlay:
- regular chains
- irregular species
non-GPC separation of
irregular species
Structure elucidation of
by-product currently
investigated
PSS - WatersSymposium
International
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GPC/SEC
2013 & Related techniques, Amsterdam,
www.pss-polymer.com
September 28, 2016
Page 17
Conclusions
GPC/SEC with ESI-MS detection can be used to
• determine absolute MWD without GPC standards,
suitable for oligomers and polymers < 50000 g/mol
• identify and quantify endgroups, cyclic molecules, byproducts, homo- and binary copolymers
• investigate and optimize reaction mechanisms/products
• determine low molecular weight components (REACH
registration, deformulation, trace identification, etc.)
PSS WinGPC UniChrom software developments allow
• automated GPC-MS data processing (true MWD with
chromatographic band broadening correction)
• implementation of GPC-MS as a routine analysis method
International Symposium GPC/SEC & Related techniques, Amsterdam, September 28, 2016
Comprehensive GPC-MS
GPC-MS combines benefits of both
GPC (separation) and MS (information content)
Qualitative information
Quantitative information
Chemical structure of the macromolecules
Molecular weight distribution
(repeating units, functional endgroups,
backbone structure)
Concentration of individual functional
macromolecules in mixtures
Band-broadening correction
• Obtained from MS-Detector alone
• Molecular formula with FT/ICR or
Orbitrap
• Obtained from concentration detector with
internal calibration by ESI-MS
 Requires sophisticated data treatment
• Increased information content from
MS/MS
• Multiple charging allows M < 50.000 Da
to be analyzed
International Symposium GPC/SEC & Related techniques, Amsterdam, September 28, 2016
Backup Slides
International Symposium GPC/SEC & Related techniques, Amsterdam, September 28, 2016
Benefits and Pitfalls of MS
Advantages of Modern MS
•
•
•
•
•
Direct molar mass measurement with soft ionization
Very high resolution
Ultra high sensitivity (e.g. trace compounds, 2D detection)
High specificity
Identification and structure elucidation (by fragmentation)
Potential Problems
Selective ionization & degradation in ion source
• Broad distributions cause problems in detector
• Operation of MS instrument requires “MS expert” (“auto-tune”)
• Interpretation of data; multiple charges in ESI (“better software”)
• Quantitative results require in-depth data treatment
… cost of MS instrumentation
•
DSP Meeting, Eindhoven, April 2012
Page 21
Implementation into
WinGPC Software
Automatic charge state assignment just requires
knowledge of (co)monomer molar masses
Data analysis results:
- charge state
- chain length
- endgroup mass
- repeat unit masses
- irregular chains
- absolute M and MWD
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GPC/SEC
2013 & Related techniques, Amsterdam,
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Absolute Copolymer
MWD Determination
PEO/PPO block copolymer („pluronics“)
Na+
- Automated copolymer analysis requires comonomer Mr
- Cross-autocorrelation of residuals
O
O
n
O
H
m
Accurate determination of
copolymer molar masses
Autometic generation of
calibration curves for
different species
Automatic assignment of
charge states
PSS - WatersSymposium
International
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GPC/SEC
2013 & Related techniques, Amsterdam,
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September 28, 2016
Page 23
Detection Techniques
I = KD ×
∑ (k
Sample
× cSample × M x )
i
concentration detector:
light scattering detector:
viscometer:
mass spectrometer:
X=0
X=1
X = MH-α
X = -1
apparent concentration
scattering intensity
specific viscosity
total ion count, spectra
→ c(V)
→ M(V), Rg(V)
→ [η](V)
→ M(V), structure
6.0
I LS (V)
5.5
5.0
4.5
I osm (V)
Voltage [V]
4.0
3.5
I visco (V)
3.0
2.5
2.0
PSS WinGPC scientific
1.5
1.0
I conc (V)
0.5
0.0
13
14
15
16
17
18
19
20
Elution Volume [ml]
24
International
PSS - WatersSymposium
Meeting, July
GPC/SEC
2013 & Related techniques, Amsterdam,
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September 28, 2016
Experimental Setup GPC-ESI-MS
Plumbing Details
Lab View
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International
Meeting, July
GPC/SEC
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Ternary Mixture
- Reconstruction of the molecular weight distributions of a
ternary mixture is possible
- Overall good agreement between molar mass averages and PDI
2.0:2.0:2.0 g∙L-1
original
reconstructed
DPw
DPn
PDI
∫
DPw
DPn
PDI
∫
pMMA(H-H)
manufacturer
46.6
50.0
41.5
45.4
1.12
1.09
195
45.8
(-2%)
41.6
(0%)
1.10
200
(+3%)
pMMA(BriB)
52.6
47.4
1.11
195
49.8
(-5%)
45.2
(-5%)
1.10
185
(-5%)
pMMA(CPDB)
25.5
15.6
1.64
215
27.4
17.0
(+7%) (+8%)
1.61
220
(+2%)
Gruendling, T.; Barner-Kowollik C.; Guilhaus, M. Macromolecules 2009, 42, 6366-6374.
Gruendling, T.; Barner-Kowollik C.; Guilhaus, M. Anal. Chem. 2008, 80, 6915-6927.
PSS
- WatersSymposium
Meeting, July
2013 & Related techniques, Amsterdam,
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International
GPC/SEC
September 28, 2016
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