GPC/SEC with Mass Spectrometry Detection: A Winning Team? · • MWD determined solely by MALDI (internal mass bias correction) A Excellent agreement SRM data with GPC -ESI-MS results

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


Matching up Two Worlds

Page 3 International Symposium GPC/SEC & Related techniques, Amsterdam, September 28, 2016

Macromolecules vs. Mass Spectrometry all: high molar mass gas phase separation most: solid of ionized species in high vacuum not a simple start …



GPC/SEC Systems vs. Mass Spectrometers

not simple either …



Advantages and Limitations of GPC/SEC Mass Spectrometry + standard technique - limited by high price + applicable to all macromolecules - exotic with polymers + can separate mixtures - difficult spectra of mixtures + non-specific detection - risk of ion suppression o separates by size + direct molar mass measurement - low resolution + high resolution - unspecific (in general) + high specificity/identification - difficult to detect traces + high sensitivity (very low LOD) - co-eluting species + independent separation in MS + software for specific data treatment - no specific software for polymers Good balance of pros/cons hyphenation has potential


fractions from GPC/SEC separation

MS control + requires powerful PC, creates large data sets

MS

Major Problem: - generate gas phase species from charged solid analytes

How To Hyphenate

7

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


How To Hyphenate


column visco RI Information content:

Primary: [η] Mw c Mn Secondary: M, g‘ Rg, g - endgroup, structure structure - repeat units, by-products, etc., …

LS MS

5

10

15

20

25

30

35

40

45

Elution volume [ml]

5.0 7.5 10.0 12.5 15.0 17.5 20.0 22.5 25.0 27.5 30.0

RI Sign

al [mV

]

PSS Win

GPC Un

ity, Buil

d 3523,

LAB-SW

1, Instan

ce #1

? ?

? ?

Understanding local polydispersity: measure Mw (LS) / Mn (MS)

How To Hyphenate

GPC-MS combines benefits of both GPC (separation) and MS (information content)


Qualitative information (Status quo ante)

Chemical structure of the macromolecules (repeating units, functional endgroups, backbone structure) • 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

Quantitative information (Current state-of-the-art)

Molar mass distribution & averages Concentration of individual macromolecular species in mixtures Band-broadening correction • Obtained from concentration detector with internal calibration by MS Requires sophisticated data treatment Convolution of EIC’s to fit RI mass

Information Content

Page 10

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


Information Content


Single Oligomer Profiles (SOP) = Extracted Ion Chromatogram

Mass Spectrum

1200 1250 1300 1350 1400 1450 1500 1550 1600 1650 1700 1750 1800 m/z

1475

.50

1425

.42

1525

.50

1375

.42

1464

.83

1514

.75

1575

.50

1414

.75

1564

.92

1325

.25

1625

.58

1615

.00

1364

.83

1664

.92

1675

.58

1275

.25

1314

.75

0 2 4 6 8 10 12 14 16 18 20 22 retention time /min

Total mass concentration of polymer

Peak dispersion, σ, τ

Retention time, tR

monomer units, functional endgroups, backbone structure

Area, A

10 12 14 16 18 20 22 24

RI signal

retention time /min

SEC-calibration, relative abundance of oligomers

Investigtion of binary polymer blend

GPC: - endgroups co-elute MS: - can separate/identify - reveals sample mixture

Binary mixture of two functional polymers

Brn

O OMe

O

MeO

HH

n

O OMe

? ?

frac

tion

Information Content

Comparison with NIST SRM2881:

• Absolute molecular weight polystyrene standard • MWD determined solely by MALDI (internal mass bias correction)

Excellent 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

HBu

n

Ag+

MS generated calibration


GPC-MS with MaxEnt corrects for peak broadening

– Only slight effects due to good column resolution

– Important for oligomer analysis

25 75 125 1756.0

6.5

7.0

7.5

V G /c

m3

repeat unit (n)

chargestate6

54

3

0 50 100 150 2000.00

0.01

0.02

0.03

w(n)

repeat unit (n)

Results based on DPw DPn PDI

Manufacturer 102.00 99.00 1.03

NMR (bulk) 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 Gruendling et al., Anal. Chem. 2008, 80, 6915-6927.

repeat unit (DP)

repeat unit (DP)

Verification of Data Processing

PSS - Waters Meeting, July 2013 www.pss-polymer.com

MS Data Analysis with WinGPC Software

Page 14

What Can We Learn from GPC with MS Detection Raw Data View of Unknown

Observations: - simple charge pattern - good mass resolution - 2 main distributions same repeat units ∆m/e: 86.089 amu

Automatic identification - poly(methyl acrylate) - 2 endgroups propyl (43), butyl (57)




Page 15

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




Page 16

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




Page 17

Analysis of Poly(methyl acrylate) by GPC-MS Sample characteristics with correct and incorrect assignment

MWD overlay: - regular chains - irregular species non-GPC separation of irregular species Structure elucidation of by-product currently investigated

regular irregular Mn [Da] 1614 7529 Mw [Da] 2105 7537 PDI 1.30 1.001


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, by-

products, 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

Conclusions


GPC-MS combines benefits of both GPC (separation) and MS (information content)

Comprehensive GPC-MS

Qualitative information Chemical structure of the macromolecules (repeating units, functional endgroups, backbone structure) • Obtained from MS-Detector alone • Molecular formula with FT/ICR or

Orbitrap • Increased information content from

MS/MS • Multiple charging allows M < 50.000 Da

to be analyzed

Quantitative information Molecular weight distribution Concentration of individual functional macromolecules in mixtures Band-broadening correction • Obtained from concentration detector with internal calibration by ESI-MS Requires sophisticated data treatment

Backup Slides


Benefits and Pitfalls of MS

Page 21 DSP Meeting, Eindhoven, April 2012

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


Implementation into WinGPC Software

Page 22

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


Absolute Copolymer MWD Determination

PEO/PPO block copolymer („pluronics“) - Automated copolymer analysis requires comonomer Mr

- Cross-autocorrelation of residuals

PSS - Waters Meeting, July 2013 www.pss-polymer.com Page 23

Accurate determination of copolymer molar masses Autometic generation of calibration curves for different species Automatic assignment of charge states

On

Na+

OO

m

H


24

Detection Techniques

concentration detector: X = 0 apparent concentration → c(V) light scattering detector: X = 1 scattering intensity → M(V), Rg(V) viscometer: X = MH-α specific viscosity → [η](V) mass spectrometer: X = -1 total ion count, spectra → M(V), structure

I K k c MD Sample Samplei

x= × × ×∑ ( )

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

Elution Volume [ml]13 14 15 16 17 18 19 20

Volta

ge [V

]

PSS

Win

GPC

sci

entif

ic

I (V)LS

I (V)visco

I (V)osm

I (V)conc

PSS - Waters Meeting, July 2013 www.pss-polymer.com International Symposium GPC/SEC & Related techniques, Amsterdam, September 28, 2016


Experimental Setup GPC-ESI-MS

Page 25

Plumbing Details

Lab View


- Reconstruction of the molecular weight distributions of a ternary mixture is possible - Overall good agreement between molar mass averages and PDI


Ternary Mixture

Page 26

2.0:2.0:2.0 g∙L-1

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.

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

(+7%) 17.0

(+8%) 1.61

220

(+2%)


Presenter

Presentation Notes

090117\C-pMMA(CPDB,BriB3,5000)(2,0-2,0-2,0)mg_ml

Documents

GPC/SEC with Mass Spectrometry Detection: A Winning Team? · • MWD determined solely by MALDI (internal mass bias correction) A Excellent agreement SRM data with GPC -ESI-MS results