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Handbook of Size Exclusion Chromatography and Related ...

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Figure 18 Wheat glucan.Elution pr<strong>of</strong>ile triplet: massby DRI !raw mass ev; (—B—)<br />

[Eqs (6) <strong>and</strong> (7)]. Applied laser intensity ! raw LS 0; (—4—). Scattered<br />

laser intensity ! raw LS 5(—†—) SEC system: TosoHaas guard PWH þ GMPWM þ<br />

GMPW6000 þ 5000 þ 4000 þ 3000 (150 7.5 mm); eluent, 0.1 M NaCl(aq) þ 0.005 M<br />

Na2CO3(aq) þ NaN3; flow rate, 0.80 mL/min; sample (inject) volume, 0.4 mL (5 mg/mL).<br />

Depending on the applied dissolution process <strong>and</strong> the characteristics<br />

<strong>of</strong> superimposed glucan aggregates, molecular weights in the range <strong>of</strong> several<br />

10 7 g/molwill typically be achievedfrom light-scattering data (Figs 19c <strong>and</strong> 20).<br />

Even for extremely long periods <strong>of</strong> dissolution only minor changes in molecular<br />

weight will be observed; supermolecular structures are still present <strong>and</strong> dominate<br />

the light-scattering signal. Thus, although absolute, light scattering primarily<br />

provides information about molecular weight <strong>of</strong> glucan aggregates <strong>and</strong> not <strong>of</strong><br />

constituting glucan molecules.<br />

5.3.3 Mass/Viscosity: Excluded Volume Pr<strong>of</strong>ile<br />

If SEC separation <strong>of</strong> starch glucans is connected with mass <strong>and</strong> viscosity<br />

detection, excluded volume pr<strong>of</strong>ile <strong>and</strong> overlapping concentration pr<strong>of</strong>ile may be<br />

obtained (Fig. 21).<br />

The specific viscosity pr<strong>of</strong>ile (eta spec) is computed according to Eq. (18)<br />

from monitored typically constant inlet pressure pr<strong>of</strong>ile (raw ip) <strong>and</strong> differential<br />

pressure pr<strong>of</strong>ile (raw dp).<br />

eta spec ¼<br />

4raw dp<br />

raw ip 2raw dp<br />

(18)<br />

Combining specific viscosity pr<strong>of</strong>ile <strong>of</strong> starch glucans with mass<br />

information (mass ev,actual fraction mass: inj mass) for each SEC separated<br />

© 2004 by Marcel Dekker, Inc.

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