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4 LC/ MS of Polymers

4 LC/ MS of Polymers

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TABLE 4.2

Selected Publications on the Characterization of Oligomeric/

Polymeric Samples by ESI or APCI Mass Spectrometry

Combined with On-Line Separation

Analyte

PEG

Poly(tetrahydrofuran)

Polystyrene

Polyesters



Amino resins



Phenolic resins

Poly(propylene imine)

dendrimers

Oligomeric surfactants



Separation



Interface



Refs.



SEC

SEC

SEC

SEC

GPEC

RPLC

SEC

RPLC

RPLC

CE

SFC

(SEC)

RPLC



ESI

ESI

ESI

ESI

ESI

APCI

ESI

ESI

APCI

ESI

APCI

(PB-EI)

ESI



75

8

8

8, 42, 89, 96

88

76–78

73

79, 80

74, 80

74

81

(75)

82



SEC



ESI



93–95



SEC: size-exclusion chromatography; RPLC: reversed-phase liquid

chromatography; GPEC: gradient polymer elution chromatography;

CE: capillary electrophoresis; SFC: supercritical-fluid chromatography; EI: electron ionization; PB: particle beam.



LC techniques for synthetic polymers can be categorized according to their

mode of operation. Figures 4.9 to 4.11 illustrate different modes that may

afford separation of oligomers and their mixtures according to specific molecular properties for an oligomeric surfactant Triton X-100 [octylphenoxypoly(ethoxy)ethanol] as an example. Figure 4.9 shows the total ion current

(TIC) chromatogram, along with the contour plot (m/z on the axis vs. chromatographic elution time on the horizontal axis, and shaded areas in the x-y

plane indicate ESI ions with intensity exceeding the threshold), for a normalphase separation by gradient elution. In this mode of LC, the oligomers are

separated, but the elution of different oligomeric series (I-IV) that reflect

chemical heterogeneities overlap.

A reversed-phase LC-ESI-MS analysis of Triton X-100 is shown in Figure 4.10,

which displays separation according to chemical heterogeneity practically

independent of molecular size.The chromatographic resolution of oligomeric

mixtures may also rely on liquid adsorption chromatography (LAC, performed usually on silica gel as a stationary phase) and gradient polymer

elution chromatography (GPEC). In LAC, all sample components initially

prefer to adsorb on the surface of the stationary phase, and the increase in

the percentage of a strong solvent (displacer) results in the sequential elution

according to the change in the adsorption equilibria involving the analyte

83

molecules, the stationary phase, and the mobile phase. To date, no application of LAC coupled with ESI/APCI mass spectrometry has been reported.

©2002 CRC Press LLC



FIGURE 4.9

TIC chromatogram (bottom chart) and contour plot for the LC-ESI-MS analysis of Triton X-100,

an oligomeric surfactant, by using gradient normal-phase chromatography (2 mm i.d. cyanopropylsilica column, from 95/5 hexane/dichloromethane to 50/40/10 hexane/dicholomethane/

methanol in 20 min, 200 µL/min flow rate, no effluent split, nebulizer-assisted electrospray),

and the oligomer series identified (I-IV). The m/z values of the peaks that belong to the major

+

oligomer series (I) follow the formula [M + NH4 ] = 224 + 44n, where n is the number of ethoxy

2+

units, and doubly charged [M + 2NH4] ions are also present. (Courtesy of PE Sciex, Foster

City, CA)



©2002 CRC Press LLC



FIGURE 4.10

TIC chromatogram (bottom chart) and contour plot for the LC-ESI-MS analysis of Triton X-100,

by using gradient reversed-phase chromatography [2 mm i.d. octadecylsilica column, 20/80 to

50/50 acetonitrile/10 mM ammonium acetate in 20 min, 200 µL/min flow rate, 3:1 effluent split,

nebulizer-assisted electrospray]. See Figure 4.9 for the oligomer series (I-IV) separated. (Courtesy of PE Sciex, Foster City, CA)



In GPEC (also known as high-performance precipitation liquid chromatography),84–87 the oligomeric mixture is dissolved in a good solvent of the

analyte and injected onto the column equilibrated with a poor solvent (“nonsolvent”) as an initial mobile phase that results in the precipitation of the

polymer on the top of the column. An increasing percentage of the good

solvent during gradient elution will redissolve the oligomer molecules

according to both their molecular weight and chemical composition. Ideally,

the stationary phase does not have an effect on the separation process.

Therefore, GPEC may be performed on nonpolar stationary phases such as

88

octadecylsilica (ODS) bonded phase. GPEC/ESI-MS has been used to char89

acterize dipropoxylated bisphenol A/adipic acid polyesters. When liquid

chromatography at the critical point of adsorption (LCCC) is used, the chromatographic elution becomes independent of the molecular weight and only

depends on chemical heterogeneity. LCCC requires specific solvent composition and temperature; thus, method development is critical and may be

tedious. Experimentally less demanding gradient separations in which the

method is tuned for a mass-independent elution have been developed

(“pseudo-LCCC”; the analysis of Triton X-100 presented in Figure 4.10 may

be considered as an example) and used on-line with ESI mass spectrometry

for the analysis of alkylated poly(ethylene glycol) and terephthalic acid/

neopentyl glycol polyester resin. Because the separation does not significantly decrease the polydispersity of the analyte in this hyphenated technique,

ESI mass spectrometry is useful mainly for identification of the oligomers, and

as a support to LC method development and LC-based quantification.

©2002 CRC Press LLC



SEC, which is also known as gel permeation chromatography (GPC), is

the most commonly used method for determining polymer molecular

90

weight distributions (MWD). This LC method separates compounds based

on their hydrodynamic volume in solution; larger molecular size materials,

higher molecular weight, eluting first followed by the smaller molecules of

lower molecular weight. The commonly used differential refractive index

(RI) detector provides, again, very little information about the chemical

composition, and molecular weight information obtained by the technique

is highly dependent on the accuracy of the calibration procedure. Although

a well-defined relationship exists only between the hydrodynamic volume

(not molecular weight) of the solute and its retention volume (VR), the common logarithm of relative molecular weight (log Mr) is correlated to VR in

practice. Well-characterized, narrow molecular weight distribution oligomer

and polymer calibrants of similar chemical composition provide the most

accurate results. Such calibrants are usually unavailable, and narrow molec91

ular weight polystyrene standards are often used. Besides, the mechanism

of separation in SEC may involve solute-solvent-packing interactions that

92

are not strictly dependent on molecular size, and such interactions may

lead to systematic errors in estimation of the molecular weight relying on

calibration curves obtained by polystyrene standards when measuring polymers other than polystyrene. The SEC analyses of oligomeric mixtures may

suffer the most from structure-dependent interactions. Oligomers of dissimilar chemical composition can also assume significantly different hydrodynamic volumes depending on their conformation in solution, even though

their Mr is identical.

ESI mass spectrometry is compatible with the SEC conditions applied to

the routine analysis of synthetic oligomers and polymers, and the coupling

offers specific benefits in terms of obtaining chemical composition information

93,94

and accurate molecular weight calibration.

Figure 4.11 shows the GPC/

ESI-MS analysis of Triton X-100. [No cationizing agent is added to the tetrahydrofuran mobile phase; therefore, the major ions represented in the

contour plot are the protonated octylphenoxypoly (ethoxy)-ethanol oligomers

with m/z = 207 + 44n.] Most GPC/ESI-MS applications have relied on the

pre-column or post-column addition of a cationizing agent, most commonly

NaI which has good solubility in the mobile phase. ESI mass spectrometry

can directly handle effluents from analytical (7.8-mm i.d.) SEC columns with

very little (<1%) of that effluent required (spectra are recorded from ∼10 ng of

sample during elution). This approach results in a significant decrease in the

polydispersity of the analyte entering the ion source of the mass spectrometer, as demonstrated in Figure 4.11; therefore, problems associated with the

ESI-MS analysis of polymeric samples with broad molecular weight distribution (discrimination according to cationization efficiency as a function of

molecular weight, bias based on detection efficiencies, choice of experimental

conditions, and so on) are eliminated or greatly reduced. With the mass

spectrometer continually acquiring spectra as the molecules elute from the

SEC, an on-line absolute molecular weight detector is employed for polymers

©2002 CRC Press LLC



FIGURE 4.11

TIC chromatogram (bottom chart) and contour plot for the SEC-ESI-MS analysis of Triton X-100

(30 cm ì 7.8 mm i.d. PLGel 3-àm Mixed-E column, tetrahydrofuran mobile phase at 1.0 mL/

min, effluent split 1:100). Major ions are the protonated oligomers.



that have been size-separated by the SEC. From the mass spectra, the elution

profiles of individual oligomers are determined from the reconstructed

selected ion current as a function of elution time (tR) or elution volume, VR.

Because ESI uses only a very small fraction of the effluent, conventional SEC

detectors (RI, UV, and the like) can be operated parallel with mass spectrometry. The peak apex for each selected ion chromatogram or selected oligomer

profile (the sum of ion intensities over different charge states) is used for an

accurate elution volume for the given oligomer mass, which is then used to

generate a calibration curve as shown in Figure 4.12. To better demonstrate

the effect of using an SEC calibration obtained by coupling with ESI mass

spectrometry vs. calibration with narrow-dispersity polystyrene standards,

an octylphenoxypoly(ethoxy)ethanol sample with higher average molecular

weights and broader molecular distribution (Igepal), compared to Triton X100, was used as an analyte. In Table 4.3, a comparison of quantitative

molecular weight distribution data obtained by direct ESI, analytical SEC

with polystyrene calibration, and SEC after accurate ESI mass spectrometric

calibration is presented. A recent development in GPC/ESI-MS includes

miniaturization of the column (µSEC) that offers various advantages to the

technique, such as low eluent consumption, low cost per column, reduced

maintenance requirement, ability to interface to other chromatographic

©2002 CRC Press LLC



FIGURE 4.12

n+

a) UV chromatogram (λ = 254 nm) and [M + nNa] selected-ion traces for octylphenoxypoly

(ethoxy)ethanol oligomers separated on three SEC columns (30 cm × 7.8 mm i.d., 1000 Å, 500 Å,

and 100 Å UltraStyragel) in series. The selected-ion trace for the triply charged n = 50 oligomer

was obtained by summing m/z 824 to 826; the selected-ion trace for the doubly charged n = 35

oligomer was obtained by summing m/z 895 to 826; and the trace for the singly charged n = 20

oligomer was obtained by summing m/z 1108 to 1110 through the duration of the chromatogram. b) Calibration curves for octylphenoxypoly(ethoxy)ethanol: polystyrene vs. on-line ESI

mass spectrometry. (Reprinted with permission from Ref. 94. Copyright ©2000 American

Chemical Society.)



techniques (multidimensional LC) and the possibility of coupling to ESI mass

95

spectrometry without the need for flow splitting. In addition, better chromatographic performance can be achieved with microcolumns when compared to

conventional-bore systems, which enables a better separation of sample constituents or significantly reduced time of analysis with separation power

identical to conventional SEC columns. Newer mass analyzers such as

89

96

orthogonal acceleration time-of-flight (oa-TOF) and FT-ICR instruments

have been introduced into GPC/ESI-MS of polymers. Larger oligomers, such

©2002 CRC Press LLC



TABLE 4.3

Molecular Weight Averages and Polydispersity of an

Octylphenoxypoly(ethoxy)ethanol Oligomeric Surfactant

by Direct ESI Mass Spectrometry, SEC with Polystyrene

Calibration, and SEC with Calibration Via On-Line ESI Mass

Spectrometry

ESI mass spectrometry, no separation

SEC, polystyrene calibration

SEC, calibration by on-line ESI-MS



Mn



Mw



PD



1736

2001

1971



1771

2162

2016



1.02

1.15

1.08

5+



as poly(methyl methacrylate) (PMMA) up to 9000 Da as [M + 5Na] ions, and

minor impurities can be easily detected due to the extended mass range and

high duty cycle of the oa-TOF analyzer, compared to GPC/ESI-MS on a

quadrupole instrument or a quadrupole ion trap. Selected oligomer profiles

for the sodiated (1+ through 5+ charge states) ions were also generated for

a commercial, narrow molecular-weight-distribution PMMA sample, and

they were used for obtaining a calibration curve and calculating accurate

molecular-weight distribution data. In addition, GPC/ESI-FT-ICR mass

spectrometry of PMMA allowed for an unequivocal end-group determination and characterization of a secondary distribution due to the formation

of cyclic reaction products. A GMA/BMA copolymer with a broad molecular-weight distribution, where fractionation and high resolving power were

required for adequate characterization, has also been analyzed by this

hyphenated technique, and sodiated GMA/BMA oligomers in excess of

9 kDa were detected. End-groups resulting from the polymerization process

were positively identified, and GPC/ESI-FT-ICR also allowed the accurate

determination of the molecular weight distribution data.



4.5



Conclusion



In this chapter, the principles, instrumentation, and application of atmosphericpressure ionization (principally ESI) mass spectrometry to synthetic oligomers

and polymers are discussed through selected representative examples. The

technique has proven potential in this application area from the structural

and compositional characterization discussed here to, perhaps, preparative mass

97

spectrometry to generate monodisperse synthetic polymers. Direct use of the

technique is appropriate for the qualitative analysis of samples with moderate

complexity and molecular weight due to the phenomenon of multiple charging characteristic of ESI, and it is also well-suited under these conditions

for sophisticated structural studies involving ultra-high resolution or tandem mass spectrometry. ESI mass spectrometry of mixtures with broad

molecular weight distribution should benefit a prior separation, reducing

©2002 CRC Press LLC



the polydispersity of the analyte. The advantage of hyphenated LC/MS for

obtaining information about chemical composition, resolution of overlapping charge envelopes in the ESI mass spectra of polymers, SEC calibration,

and complex mixture analysis have been highlighted.



References

1. Dole, M., Mack, L. L., Hines, R. L., Mobley, R. C., Ferguson, L. D., and Alice, M.

B. Molecular beams of macroions. J. Chem. Phys, 49, 2240, 1968.

2. Dole, M., Cox, H. L., Jr., and Giemic, J. Adv. Chem. Ser., 125, 73, 1973.

3. Yamashita, M. and Fenn, J. B. Electrospray ion-source—Another variation on the

free-jet theme. J. Phys. Chem., 88, 4451, 1984.

4. Whitehouse, C. M., Dreyer, R. N., Yamashita, M., and Fenn, J. B. Electrospray interface for liquid chromatographs and mass spectrometers. Anal. Chem., 57, 675, 1985.

5. Zeleny, J. On the conditions of instability of liquid drops, with applications to

the electrical discharge from liquid point. Proc. Camb. Phil. Soc., 18, 71, 1915.

6. Yamashita, M. and Fenn, J. B. Negative-ion production with the electrospray ionsource. J. Phys. Chem., 88, 4671, 1984.

7. Bruins, A. P., Covey, T. R., and Henion, J. D. Ionspray interface for combined

liquid chromatography/atmospheric pressure ionization mass spectrometry.

Anal. Chem., 59, 2642, 1987.

8. Nielen, M. W. F. Characterization of synthetic polymers by size-exclusion chromatography/electrospray ionization mass spectrometry. Rapid Commun. Mass

Spectrom., 22, 57, 1996.

9. Horning, E. C., Carroll, D. I., Dzidic, I., Haegele, K. D., Horning, M. G., and

Stillwell, R. N. Atmospheric pressure ionization (API) mass spectrometry. Solventmediated ionization of samples introduced in solution and in a liquid chromatograph effluent stream. J. Chromatog. Sci., 12, 725, 1974.

10. Carroll, D. I., Dzidic, I., Stillwell, R. N., Haegele, K. D., and Horning, E. C.

Atmospheric pressure ionization mass spectrometry: Corona discharge ion

source for use in liquid chromatograph-mass spectrometer-compute analytical

system. Anal. Chem., 47, 2369, 1975.

11. Huertas, M. L. and Fontan, J. Evolution times of tropospheric positive ions.

Atmospheric Environ., 9, 1018, 1975.

12. Horning, E. C., Carroll, D. I., Dzidic, I., Lin, S. N., Stillwell, R. N., and Thenot, J.P. Atmospheric pressure ionization mass spectrometry. Studies of negative ion

formation for detection and quantification purposes. J. Chromatogr., 142, 481, 1977.

13. Bruins, A. P. Atmospheric-pressure ionization mass spectrometry. 1. Instrumentation and ionization techniques. Trends Anal. Chem., 13, 81, 1994.

14. Kebarle, P. and Tang, L. From ions in solution to ions in the gas phase—The

mechanism of electrospray mass spectrometry. Anal. Chem., 65, 972A, 1993.

15. Iribarn, J. V. and Thomson, B. A. On the evaporation of small ions from charged

droplets. J. Chem. Phys., 64, 2287, 1976.

16. Fenn, J. B., Rosell, J., and Meng, C. K. In electrospray ionization, how much pull

does an ion need to escape its droplet prison? J. Am. Soc. Mass Spectrom., 8, 1147,

1997.

17. Fenn, J. B. Ion formation from charged droplets: Roles of geometry, energy, and

time. J. Am. Soc. Mass Spectrom., 4, 524, 1993.

©2002 CRC Press LLC



18. Wong, S. F., Meng, C. K., and Fenn, J. B. Multiple charging in electrospray

ionization of poly(ethylene glycols). J. Phys. Chem., 92, 546, 1988.

19. Keese, R. G. and Castleman, A. W., Jr. J. Phys. Chem. Ref. Data, 15, 1011, 1986.

20. Schwartz, B. L., Rockwood, A. L., Smith, R. D., Tomalia, D. A., and Spindler, R.

Detection of high molecular weight starburst dendrimers by electrospray ionization mass spectrometry. Rapid Commun. Mass Spectrom., 9, 1552, 1995.

21. Smith, R. D., Loo, J. A., Ogorzalek-Loo, R. R., Busman, M., and Udseth, H. R.

Principles and practice of electrospray ionization—Mass-spectrometry for large

polypeptides and proteins. Mass Spectrom. Rev., 10, 359, 1991.

22. Nohmi, T. and Fenn, J. B. Electrospray mass spectrometry of poly(ethylene glycols) with molecular weights up to five million. J. Am. Chem. Soc., 114, 3241, 1992.

23. Latourte, L., Blais, J.-C., Tabet, J.-C., and Cole, R.B. Desorption behavior and

distribution of fluorinated polymers in MALDI and electrospray ionization mass

spectrometry. Anal. Chem., 69, 2742, 1997.

24. Guittard, J., Tessier, M., Blais, J. C., Bolbach, G., Rozes, L., Maréchal, E., and Tabet,

J. C. Electrospray and matrix-assisted laser desorption/ionization mass spectrometry for the characterization of polyesters. J. Mass Spectrom., 31, 1409, 1996.

25. Deery, M. J., Jennings, K. R., Jasieczek, C. B., Haddleton, D. M., Jackson, A. T.,

Yates, H. T., and Scrivens, J. H. A study of cation attachment to polystyrene by

means of matrix-assisted laser desorption/ionization and electrospray ionizationmass spectrometry. Rapid Commun. Mass Spectrom., 11, 57, 1997.

26. Mahon, A., Kemp, T. J., Buzy, A., and Jennings, K. R. Mass-spectral characterization

of oligomeric polysulfides by electrospray ionization combined with collisioninduced decomposition. Polymer, 37, 531, 1996.

27. Barton, Z., Kemp, T. J., Buzy, A., Jennings, K. R., and Cunliffe, A. V. Mass-spectral

characterization of linear and cyclic forms of oligomeric nitrated polyethers by

electrospray ionization: Specific cationization effects in cyclic polyethers. Polymer, 38, 1957, 1997.

28. Mahon, A., Kemp, T. J., Buzy, A., and Jennings, K. R. Electrospray ionization

mass spectrometric study of oligomeric linear polysulfides: Characterization of

repeat units, end groups and fragmentation pathways. Polymer, 38, 2337, 1997.

29. Hunt, S. M., Binns, M. R., and Sheil, M. M. Structural characterization of polyester

resins by electrospray mass spectrometry. J. Appl. Polym. Sci., 56, 1589, 1995.

30. Yalcin, T., Gabryelski, W., and Li, L. Structural analysis of polymer end groups

by electrospray ionization high-energy collision-induced dissociation tandem

mass spectrometry. Anal. Chem., 72, 3847, 2000.

31. Koster, S., Duursma, M. C., Boon, J. J., Nielen, M. W. F., De Koster, C. G., and

Heeren, R. M. A. Structural analysis of synthetic homo- and copolyesters by

electrospray ionization on a Fourier transform ion cyclotron resonance mass

spectrometer. J. Mass Spectrom., 35, 739, 2000.

32. Adamus, G., Sikorska, W., Kowalczuk, M., Montaudo, M., and Scandola, M.

Sequence distribution and fragmentation studies of bacterial copolyester macromolecules: Characterization of PHBV macroinitiator by electrospray ion-trap

multistage mass spectrometry. Macromolecules, 33, 5797, 2000.

33. Simonsick, W. J., Jr. and Prokai, L. ESI and tandem mass spectrometry of mixed

polyesters. Proceedings of the 48th ASMS Conference of Mass Spectrometry and Allied

Topics, Long Beach, CA, June 11–15, 2000, CD-ROM: MODpm.pdf.

34. Adamus, G. and Kowalczuk, M. Electrospray multistep ion trap mass spectrometry for the structural characterisation of poly[(R,S)-3-hydroxybutanoic acid]

containing a β-lactam end group. Rapid Commun. Mass Spectrom., 14, 195, 2000.

©2002 CRC Press LLC



35. Stolarzewicz, A., Morejko-Buz, B., and Neugebauer, D. Study of the structure of

poly(methyl methacrylate) obtained in the presence of potassium hydride. Rapid

Commun. Mass Spectrom., 14, 2170, 2000.

36. Mann, M., Meng, C. K., and Fenn, J. B. Interpreting mass spectra of multiply

charged ions. Anal. Chem., 61, 1702, 1989.

37. Reinhold, B. B. and Reinhold, V. N. Electrospray ionization mass spectrometry:

Deconvolution by an entropy-based algorithm. J. Am. Soc. Mass Spectrom., 3, 207, 1992.

38. Zhang, Z. and Marshall, A. G. A universal algorithm for fast and automated

charge state deconvolution of electrospray mass-to-charge ratio spectra. J. Am.

Soc. Mass Spectrom., 9, 225, 1998.

39. Kallos, G. J., Tomalia, D. A., Hedstrand, D. M., Lewis, S., and Zhou, J. Molecular

weight determination of a polyamidoamine starburst polymer by electrosprayionization mass spectrometry. Rapid Commun. Mass Spectrom., 5, 383, 1991.

40. O’Connor, P. B. and McLafferty, F. W. Oligomer Characterization of 4-23 kDa

polymers by electrospray Fourier transform mass spectrometry. J. Am. Chem.

Soc., 117, 12826, 1995.

41. Ross, C. W., III. and Simonsick, W. J., Jr. Proceedings of the 44th ASMS Conference

on Mass Spectrometry and Allied Topics, Portland, OR, May 12–16, 1996, p. 1270.

42. Simonsick, W. J., Jr., Aaserud, D. J., Grady, M. C., and Prokai, L. Gel permeation

chromatography coupled to Fourier transform mass spectrometry for the characterization of the products of methacrylate polymerizations. Polym. Prepr. (Am.

Chem. Soc., Div. Polym. Chem.), 38, 483, 1997.

43. Shi, S. D.-H., Hendrickson, C. L., Marshall, A. G., Simonsick, W. J., Jr., and

Aaserud, D. J. Identification, composition, and asymmetric formation mechanism of glycidyl methacrylate/butyl methacrylate copolymers up to 7000 Da

from electrospray ionization ultrahigh resolution Fourier transform ion cyclotron

resonance mass spectrometry. Anal. Chem., 70, 3220, 1998.

44. Koster, S., Duursma, M. C., Boon, J. J., and Heeren, R. M. A. Endgroup determination of synthetic polymers by electrospray ionization Fourier transform ion

cyclotron resonance mass spectrometry. J. Am. Soc. Mass Spectrom., 11, 536, 2000.

45. McEwen, C. N., Simonsick, W. J., Jr., Larsen, B. S., Ute, K., and Hatada, K. The

fundamentals of applying electrospray ionization mass spectrometry to low mass

poly(methyl methacrylate) polymers. J. Am. Soc. Mass Spectrom., 6, 906, 1995.

46. Barton, Z., Kemp, T. J., Buzy, A., and Jennings, K. R. Mass spectral characterization of the thermal degradation of poly(propylene oxide) by electrospray and

matrix-assisted laser desorption ionization. Polymer, 36, 4927, 1995.

47. Saf, R., Mirtl, C., and Hummel, K. Electrospray ionization mass spectrometry as

an analytical tool for non-biological monomers, oligomers and polymers. Acta

Polym., 48, 513, 1997.

48. Montaudo, G., Montaudo, M. S., Puglisi, C., and Samperi, F. Molecular weight

determination and structural analysis in polydisperse polymers by hyphenated

gel permeation chromatography matrix-assisted laser desorption ionization—

Time of flight mass spectrometry. Int. J. Polym. Anal. Charact. 3, 177, 1997.

49. Maziarz, P. E. III, Baker, G. A., Mure, J. V., and Wood, T. D. A comparison of electrospray versus nanoelectrospray ionization Fourier transform mass spectrometry

for the analysis of synthetic poly(dimethylsiloxane)/poly(ethylene glycol)

oligomer blends. Int. J. Mass Spectrom., 202, 241, 2000.

50. Jasieczek, C. B., Buzy, A., Haddleton, D. M., and Jennings, K. R. Electrospray

ionization mass spectrometry of poly(styrene). Rapid Commun. Mass Spectrom.,

10, 509, 1996.

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51. Hunt, S. M., Sheil, M. M., Belov, M., Derrick, P. J. Probing the effects of cone

potential in the electrospray ion source: Consequences for the determination of

molecular weight distributions of synthetic polymers. Anal. Chem., 70, 1812, 1998.

52. Maziarz, E. P., III, Baker, G. A., Lorenz, S. A., and Wood, T. D. External ion accumulation of low molecular weight poly(ethylene glycol) by electrospray ionization

Fourier transform mass spectrometry. J. Am. Soc. Mass Spectrom., 10, 1298, 1999.

53. Saf, R., Mirtl C., and Hummel, K. Electrospray mass-spectrometry using potassiumiodide in aprotic organic solvents for the ion formation by cation attachment.

Tetrahedron Lett., 35, 6653, 1994.

54. Varray, S., Aubagnac, J.-L., Lamaty, F., Lazaro, R., Martinez, J., and Enjalbal, C.

Poly(ethylene glycol) in electrospray ionization (ESI) mass spectrometry. Analusis,

28, 263, 2000.

55. Maekawa, M., Nohmi, T., Zhan, D., Kiselev, P., Fenn, J. B. Reflections on electrospray mass spectrometry of synthetic polymers. J. Mass Spectrom. Soc. Jpn., 47,

76, 1999.

56. Nokwequ, G. M. and Bariyanga, J. Synthesis, characterization and biodegradability of a water-soluble poly(ethylene oxide) derivative polymer bearing carboxylic acid side chain function. J. Bioact. Compat. Polym., 15, 503, 2000.

57. Chen, R., Tseng, A. M., Uhing, M., and Li, L. Application of an integrated matrixassisted laser desorption/ionization time-of-flight, electrospray ionization mass

spectrometry and tandem mass spectrometry approach to characterizing complex polyol mixtures. J. Am. Soc. Mass Spectrom., 12, 55, 2001.

58. Crowther, M. W., O’Connell, T. R., and Carter, S. P. Electrospray mass spectrometry for characterizing polyglycerols and the effects of adduct ion and cone

voltage. J. Am. Oil Chem. Soc., 75, 1867, 1998.

59. Arakawa, R., Watanabe, T., Fukuo, T., and Endo, K. Determination of cyclic

structure for polydithiane using electrospray ionization mass spectrometry. J.

Polym. Sci., Part A: Polym. Chem., 38, 4403, 2000.

60. Focarete, M. L., Scandola, M., Jendrossek, D., Adamus, G., Sikorska, W., and

Kowalczuk, M. Bioassimilation of atactic poly[(R,S)-3-hydroxybutyrate] oligomers by selected bacterial strains. Macromolecules, 32, 4814, 1999.

61. Schwach-Abdellaoui, K., Heller, J., Gurny, R. Hydrolysis and erosion studies of

autocatalyzed poly(ortho esters) containing lactoyl-lactyl acid dimers. Macromolecules, 32, 301, 1999.

62. Jasieczek, C.B., Buzy, A., Haddleton, D. M., and Jennings, K. R. Electrospray

ionization mass spectrometry of poly(styrene). Rapid Commun. Mass Spectrom.,

10, 509, 1996.

63. vanHest, J. C. M., Delnoye, D. A. P., Baars, M. W. P. L., Elissen-Roman, C.,

vanGenderen, M. H. P., and Meijer, E. W. Polystyrene-poly(propylene imine)

dendrimers: Synthesis, characterization, and association behavior of a new class

of amphiphiles. Chem. Eur. J., 2, 1616, 1996.

64. Scrivens, J. H. and Jackson, A. T. Characterization of synthetic polymer systems.

Int. J. Mass Spectrom., 200, 261, 2000.

65. Schwartz, B. L., Rockwood, A. L., Smith, R. D., Tomalia, D. A., and Spindler, R.

Detection of high molecular weight starburst dendrimers by electrospray ionization mass spectrometry Rapid Commun. Mass Spectrom., 9, 1552, 1995.

66. Maziarz, E.P., Baker, G.A., and Wood, T.D. Capitalizing on the high mass accuracy of electrospray ionization Fourier transform mass spectrometry for synthetic

polymer characterization: A detailed investigation of poly(dimethylsiloxane).

Macromolecules, 32, 4411, 1999.

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