Handbook of Size Exclusion Chromatography and Related ...

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4 Molecular Weight Sensitive Detectors for Size Exclusion Chromatography Christian Jackson and Howard G. Barth E. I. du Pont de Nemours and Company Wilmington, Delaware, U.S.A. 1 INTRODUCTION Size exclusion chromatography (SEC) provides a rapid, high-resolution method for determining molecular weight distributions (MWD) of macromolecules. In the conventional mode, the molecular weight is determined by calibrating the column to determine the relation between elution volume and molecular weight. The size exclusion separation mechanism is based on the effective hydrodynamic volume of the molecule, not the molecular weight, and as a result the system must be calibrated using standards of known molecular weight and homogeneous chemical composition. The chemical composition must be the same as the standards to he analyzed, and the calibrated molecular weight range must be greater than the range of molecular weights to be analyzed. The calibration curve is thus specific to a given polymer–solvent system. For many commercial polymers the columns cannot be calibrated because well-characterized standards are unavailable. The situation is further complicated © 2004 by Marcel Dekker, Inc.
for branched polymers or copolymers, for which there is no single calibration curve relating elution volume to molecular weight (1). An additional potential source of error is the sensitivity of the calibration curve to alterations in the experimental conditions. Anything that alters the elution time of a given molecular weight species, such as changes or fluctuations in flow rate, column degradation, or enthalpic interactions with the column packing, can lead to serious errors in the measurement of molecular weight. Because of these limitations, it is clearly desirable to measure the molecular weight, or some property related to molecular weight, directly as the sample elutes from the columns. This is generally done by connecting either a light-scattering detector or a viscometer to the SEC system. The eluting polymer flows through the detector cell as it leaves the column and before it reaches the concentration detector. In a light-scattering detector, the excess light scattered by the eluting polymer is proportional to molecular weight. For an on-line viscometer, the specific viscosity can be used to calculate the molecular weight either in conjunction with the Mark–Houwink coefficients of the polymer solution or by using the method of universal calibration. This chapter reviews the principles and methodology of molecular weight determination by light scattering and viscometry in conjunction with SEC. The emphasis is on those aspects of molecular weight measurement relevant to SEC analysis; more detailed general treatments of light scattering, viscometry, and polymer solutions are available elsewhere (2–10). Applications of both methods are discussed with particular emphasis on molecular weight determination of polymers that are heterogeneous in composition or architecture; it is in these areas that molecular weight sensitive detectors offer the greatest advantage over conventional SEC. 2 PRINCIPLES 2.1 Viscometry At a constant flow rate, the pressure drop across a capillary tube P is proportional to the viscosity of the liquid flowing through the tube. For a polymer solution, the ratio of this pressure to the pressure for the pure solvent P0 is equal to the relative viscosity hr of the solution, P P0 ¼ h ¼ hr h0 where h is the solution viscosity and h 0 is the solvent viscosity. The specific viscosity is defined as © 2004 by Marcel Dekker, Inc. h sp ¼ h h 0 h 0 (1) ¼ h r 1 (2)
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MARCEL DEKKER Handbook of Size Excl
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CHROMATOGRAPHIC SCIENCE SERIES A Se
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60. Modern Chromatographic Analysis
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Preface to the Second Edition Gel p
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Preface to the First Edition Molecu
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Contents Preface to the Second Edit
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17. Size Exclusion Chromatography o
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James F. Curry Analytical Departmen
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Iwao Teraoka, Ph.D. Othmer Departme
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The graphical data display typicall
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polymer molecule can elute. The tot
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individual states) allowed to them.
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unsaturation while the IR detector
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Sampleconcentrationshouldbeminimize
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averagesdefinedintermsofthemolecula
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information regarding appropriate M
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Analytical. Two models, the KMX-6 a
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Figure 6 Overlay of time-sliced pea
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accurately for very large and very
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4 GENERAL REFERENCES The interested
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46. TA Chamberlin, HE Tuinstra. US
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materials are commercially availabl
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Table 1 Commercial Column Packing M
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necessarily comparable. For this re
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adjusted such that the pore size di
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narrowmolecular weight range, indiv
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Figure 8 Effect of particle size on
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Figure 9 SEC calibration using poly
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Table 4 Typical Eluent Systems for
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Figure 12 Analysis of poly-2-vinyl
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24. E Meehan, S O’Donohue. The ro
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into accepted laboratory techniques
Page 65 and 66: Table 1 Trace Metal Impurities in C
Page 67 and 68: mass and biological activity, for m
Page 69 and 70: Experimental efficiency vs. velocit
Page 71 and 72: Table 3 Properties of SEC Silica Ge
Page 73 and 74: operate at aflow rate that can easi
Page 75 and 76: Figure 3 Efficiency of amide-bonded
Page 77 and 78: mechanically stable packing materia
Page 79 and 80: Figure 5 Pore size distributions of
Page 81 and 82: Figure 6 Separation of polystyrenes
Page 83 and 84: 60-120 A ˚ are large enough to be
Page 85 and 86: Table 6 Selected Silica-Based Colum
Page 87 and 88: Table 7 Separation Ranges for Polym
Page 89 and 90: the decline in permeability is perm
Page 91 and 92: sample components can be varied by
Page 93 and 94: Figure 10 Diol bonding reactions. I
Page 95 and 96: ecause of the higher relative molec
Page 97 and 98: valuesfork1,k2,anda,theunknownmolec
Page 99 and 100: water-soluble and detergent-soluble
Page 101 and 102: the importance of secondary retenti
Page 103 and 104: discussed in Table 8(33). Based on
Page 105 and 106: individual dispersion processes ins
Page 107 and 108: The detector time constant can dist
Page 109 and 110: 5.3 Mobile Phase A mobile phase is
Page 111 and 112: less steep and still linear at high
Page 113 and 114: 35. P Bristow, J Knox. Chromatograp
Page 115: 112. K Gooding, K Lu, G Vanecek, F
Page 119 and 120: Figure 1 “Bridge design” flow-r
Page 121 and 122: Figure 3 A light-scattering photome
Page 123 and 124: Figure 5 SEC universal calibration
Page 125 and 126: where hn is the hydrodynamic volume
Page 127 and 128: It should be noted that dn=dc also
Page 129 and 130: sensitivity for many samples compar
Page 131 and 132: that is, log[h] vs. logM,generated
Page 133 and 134: Figure 8 Effect of band broadening
Page 135 and 136: Table 1 Measurement of Molecular We
Page 137 and 138: Figure 10 Differential refractomete
Page 139 and 140: Figure 11 (A) Mark-Houwink plot of
Page 141 and 142: Table 3 Measurement of Molecular We
Page 143 and 144: size information is derived from un
Page 145 and 146: Table 5 Molecular Weight Distributi
Page 147 and 148: By measuring the scattered intensit
Page 149 and 150: 8 APPENDIX: INSTRUMENT COMPANIES 8.
Page 151 and 152: 53. G Marot, J Lesec. J Liq Chromat
Page 153 and 154: 125. D Slootmaekers, JAPP Van Dijk,
Page 155 and 156: 200. JG Bindels, GJJ Bessems, BM De
Page 157 and 158: possibly with hydrodynamic volume (
Page 159 and 160: An insurmountable limitation of SEC
Page 161 and 162: to sDR(V) when either nPS ¼nPB ¼c
Page 163 and 164: 1,4-trans;and8%1,2-vynil.TheglobalC
Page 165 and 166: The goal is to find the MWD and CCD
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As expected, pS is closer to the no
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Figure 3 Example 3: MWD and BD of a
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9. BH Zimm, WH Stockmayer. The dime
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45. RO Bielsa, GR Meira. Linear cop
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solubility properties. They are use
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determination of the absolute molec
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Figure 4 Result of the PBT analysis
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Figure 8 Result of natural spider s
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7 Size Exclusion Chromatography of
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As pointed out earlier, rubber must
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Table 2 Various Solvents and Operat
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Figure 2 Typical GPC calibrations w
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© 2004 by Marcel Dekker, Inc. Figu
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Natural and Synthetic Rubbe177 vari
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Another example, shown in Fig. 5 (3
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APPENDIX: SEC CONDITIONS FOR RUBBER
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Appendix (Continued) Polymer Column
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5. J West, E Rodriguez. Rubber Chem
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associate. Girdler (67) and Speight
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Table 1 Fractions Obtained Using Co
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Figure 1 SEC analyses of an aged as
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Apparently more polar compounds are
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40% was fractionated into four frac
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Figure 7 SEC analyses of an unaged
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Figure 9 Comparison of percentage L
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Figure 11 Comparison of SEC chromat
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Figure 12 Comparisons of SEC chroma
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percentage LMS at the other locatio
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the total area into up to 12 sectio
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attempted to develop an SEC method
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parameterisbasedontheinternalpressu
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5 MODIFIED ASPHALTS The addition of
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Oxidation of the rubber and asphalt
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Figure 20 SEC chromatogram for an a
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Figure 21 Comparisons of apparent m
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© 2004 by Marcel Dekker, Inc. S/
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PS/10 4 þ 10 3 þ 500 þ 100 THF/1
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Nevertheless, SEC of asphalts is es
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56. NW Garrick, RR Biskur. Trans Re
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Asphalts 235 122. M-S Lin, JM Chaff
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Table 1 Applications of Acrylamide
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(AM/AA), and acrylamide/dimethyldia
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polymer, a large size filter of 5,
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Figure 1 Size exclusion chromatogra
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Table3 MWandMWDofaBroad-MWDPAMStand
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Another commercially available MW d
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Table 5 Weight-Average Molecular We
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Figure 6 (a) Size exclusion chromat
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compared to anormal product. By com
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StudyingtheKineticsofaChemicalReact
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this information, the higher MW pea
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46. CJ Kim, A Hamielec, A Bendek. J
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A relatively new technique utilizin
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where ais the exponent of the Mark-
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Figure 2 TDS chromatograms for full
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Figure 5 Comparison of molecular we
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Table 3 Summary of TDS Molecular We
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thepartiallyhydrolyzedPVAwiththecol
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Table 5 Summary of Conformation and
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a¼0.627andlog(K) ¼23.249.Theseare
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The limits of detection of the PVA
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Figure 12 PVAc broad molecular weig
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4 SUMMARY Advances in SEC character
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2.1 Molecular Weight Grades of PVP
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exclusion chromatography with low-a
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weightandmolecularweightdistributio
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Figure 4 PEOcalibrationofUltrahydro
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Figure 6 Overlay of GPC chromatogra
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plus Ultrahydrogel 120 A ˚ ,Shodex
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Figure 10 SEC traces of PVP/AA copo
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Figure 11 Molecular weight distribu
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2 CHEMICAL, MACROMOLECULAR AND MORP
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Table 2 The Relative Composition of
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considered to be 3. After the DS ha
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een extensively studied by methods
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The silylation was performed in LiC
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observed using column materials hav
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Table 6 (Continued) Packing materia
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4.5 Other Cellulose Derivatives Bes
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Table 8 SEC Conditions for Characte
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dextrans swell too much in cadoxen
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stirring at room temperature for an
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Figure 2 MMDofunbleached(HP)andblea
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Figure 4 MMDofbirchkraftpulpdegrade
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adequate when evaluating the influe
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differential refractive index (DRI)
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30. HA Krässig. Effects of structu
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67. E Sjöholm, K Gustafsson, A Col
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104. B Fleury, J Dubois, C Léonard
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136. D Miller, D Senior, R Sutcliff
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166. SS Cutié, CG Smith. Determina
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200. R Berggren, F Berthold, E Sjö
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13 Molar Mass and Size Distribution
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measurements, and vapor pressure os
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The calibration of SEC columns by c
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The division according to eluent ty
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Apolymer produced by UV irradiation
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Because DMAC/LiCl is also agood sol
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compoundsandwasexplainedbyadsorptio
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isolated lignins because they are e
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The Separon HEMA and Separon HEMA B
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Figure 4 GPC elution curves of the
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liquor is highest throughout the co
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topological anisotropy in the polym
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29. M Ristolainen, R Alen, J Knuuti
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eds. Proc Int Symp 1998. Canton, Pe
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92. L Jurasek. Towards a three dime
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Table 1 Selected Industries Connect
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into C3-metabolites, which then may
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Table 4 Key Enzymes in the Biosynth
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Table 5 Cloned Mutants of Starch En
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Figure 3 Modeled x-ray diffraction
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In the native environment (plant ce
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Figure 6 (a) Large starch granules
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number of branching points); crossl
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Both absolute approaches are extrao
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Table 7 (Continued) Approach Experi
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structures, excluded volumes, and t
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Figure 10 (a) SEC elution profile o
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Figure 12 Wheat glucans: DRI elutio
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Figure 13 Wheat glucans. Normalized
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Figure 16 Wheat glucan. Normalized
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Figure 18 Wheat glucan.Elution prof
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Figure 20 Wheat glucans. Absolute m
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Figure 22 Wheat glucan. (a) Intrins
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Figure 24 Wheat PA-glucan. Elution
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an Ubbelohde-viscometer for concent
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Rheological investigations of stabi
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shifts to applied laser light, whic
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Table 8 Characteristic Parameters f
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Table 8 (Continued) and H2O. A part
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10. SG Ball, MHBJ van de Wal, RGF V
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52. W Praznik, R Beck. J Chromatogr
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3 PROTEIN PARTITIONING IN SEC 3.1 G
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Figure 1 Plot of Kav vs. log M for
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yconsideringtheproteinsolutestobesp
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globular proteins and selected flex
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silanol groups (52-54); even capped
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most proteins to be maximally stabl
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Figure 4 Chromatograms of BSA and P
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concentrated) steps of protein puri
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Table 3 Characteristics of Dextran-
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preparative SEC. The capabilities o
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37. GR Noll, N Nagle, JO Baker, DJ
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Figure 2 Separation of total E. col
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Figure 3 Separation of HaeIII-cleav
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The recovery of DNA fragments has b
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Endotoxin should also be removed fr
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Table 3 Best Columns for the Separa
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Figure 10 Dependence of HETP on flo
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Appendix (Continued ) Polymer Colum
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REFERENCES 1. CT Wehr, SR Abbott. J
Page 495 and 496:
MALDI-MS has been applied to determ
Page 497 and 498:
Figure 1 Calibration curvesof SEC c
Page 499 and 500:
Figure 3 Chromatograms of epoxy res
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wherenandn0 aretheRIsofthesample an
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Figure 5 SEC chromatogram of n-alka
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Figure 7 Refractive indexes of comm
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Another detector recently applied i
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Figure 11 Absolute MW calibration p
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Figure 12 Chromatogram of Acrawax C
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18 Two-Dimensional Liquid Chromatog
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largerispressuredropandresultingexp
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elations between molar masses and s
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Figure 2 (Continued) chapter, one o
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where Nis the column efficiency exp
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composition/architecture/molar mass
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solvent. Here again, solvent-solven
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or repulsive interactions between m
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macromolecules may strongly differ
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temperature. The efficacy of an ads
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however, aliphatic bonded groups ma
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Figure 10 Schematic representation
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packing materials for SEC of synthe
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Quantitative relations between sila
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Both strength and thermodynamic qua
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where Cand Dare constants for apart
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ThisisimportantwhenLCCCisappliedtoc
Page 547 and 548:
Page 549 and 550:
Page 551 and 552:
However, strong adsorption of macro
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elution step may be sufficient for
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Figure 16 Block scheme of a full ad
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processing of 2D-HPLC data. Knowled
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Figure 20 Set of full retention-elu
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distributions of complex polymers a
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constituents were not discriminated
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(Sec. 7) and therefore they can be
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2. Identify sample solvents. First
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1 Segmental interaction energy para
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58. BG Belenkii. Pure Appl Chem 51:
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19 Methods and Columns for High-Spe
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Table 1 Summary of Methods for Incr
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not savealot of time and solvent, d
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Figure 3 Conventional SEC chromatog
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chromatogram at 4mL/min, which is f
Page 583 and 584:
Sincethereductionoftheinternaldiame
Page 585 and 586:
Table 3 Summary of Column Performan
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Figure 11 Dependence of column perf
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. Two-dimensional chromatography ru
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The standard deviations for the mol
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Figure 15 Comparison of time requir
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Figure 17 Accuracy and precision of
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polymer analysis. Samples are “ru
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just ignoring the fractionation of
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20 Automatic Continuous Mixing Tech
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out at low enough concentration tha
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educed viscosity, h r, to be comput
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Page 609 and 610:
Figure 2 Raw ACOMP signals from mul
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Figure 4 Mw vs. monomer conversion,
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decreases smoothly and monotonicall
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Figure 7 Effects of fluctuating rea
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Finally, the use of a light-scatter
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Figure 8 Linear and cubic increases
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where r(t) is now given by 2 6 r(t)
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Figure 11 Light scattering from sol
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3.1 ASimple System: Equilibrium Cha
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Figure 13 (a) ACM applied to the ch
Page 629 and 630:
Also of note in Fig. 13b is how hig
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15. JM Starita, CL Rohn. Rheologica
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52. M Hulden. Hydrophobically modif
Page 635 and 636:
21 Light Scattering and the Solutio
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therefore, is to remove any lingeri
Page 639 and 640:
is often found in the literature wh
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Figure 2 Configuration of an SEC se
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5 THE IMPORTANCE OF SOFTWARE Like a
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standard deviations of the measured
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These include the differential weig
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Figure 8 Data of Fig. 7corrected fo
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Figure 11 Data of Fig. 10 with spik
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Figure 13 Fitstodatacollectedatasli
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Table 1 Errors (in %) Characteristi
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homogeneous copolymer, that is, tak
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process may be used to identify the
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fractionated sample. They represent
Page 663 and 664:
Figure 16 An example of poor SEC ch
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on) methods, whereby the average di
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23. WH Stockmayer, LD Moore Jr, M F
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condition, as is explained in this
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Figure 2 Partition coefficients KL
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4 COLUMNS FOR HOPC Detailsaregiveni
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and concomitant clogging of columns
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Figure 5 Concentration dependence o
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Table 1 Solution Volume, Polymer Ma
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in Fig. 4a. The middle fractions (8
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Figure 10 SEC chromatograms for som
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appropriate for the early fractions
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23 Size Exclusion/ Hydrodynamic Chr
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Figure 2 Calibration curve for the
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Figure 5 Elutionbehaviorofpolystyre
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Table 1 Comparison Between SEC and
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egular SEC column in which the pore
Page 697:
Such an ideal separation can be obt
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