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Handbook of Size Exclusion Chromatography and Related ...

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Figure 1 MALDI-MS positive ion spectra <strong>of</strong> (A) a whole Indulin AT sample, (B) a<br />

narrow MMD fraction <strong>of</strong> an Indulin AT sample isolated by SEC. (From Ref. 10.)<br />

detectors are continuously developed. New column materials are also developed,<br />

falling into three different classes <strong>of</strong> column packing materials. The rigid<br />

crosslinked polystyrene-based materials may be derivatized in order to obtain<br />

hydrophilic properties. Semirigid synthetic hydrophilic packing materials can<br />

generally be used both with aqueous <strong>and</strong> weakly alkaline eluents <strong>and</strong> also with<br />

aprotic organic eluents. S<strong>of</strong>t packing materials are mainly based on different<br />

crosslinked polysaccharides <strong>and</strong> can be used in aqueous <strong>and</strong> alkaline eluents, but it<br />

should be pointed out that when using alkaline eluents the stability <strong>of</strong> the packing<br />

materials should be continuously monitored.<br />

In several systems there are possibilties for connecting up to four different<br />

detectors that all detect the same sample as a function <strong>of</strong> Vh <strong>of</strong> the polymer molecule<br />

but measure different properties <strong>of</strong> the lignin molecule. The RI detector determines<br />

the concentration <strong>of</strong> the lignin molecules at a certain elution volume, the UV/VIS<br />

also measures the concentration <strong>of</strong> the lignin <strong>and</strong> is dependent on the extinction<br />

coefficient <strong>of</strong> the lignin, the light-scattering detectors (MALLS, LALLS) determine<br />

the size <strong>of</strong> the lignin molecules <strong>and</strong> also the interactions between lignin <strong>and</strong> the<br />

eluent. The viscosity detectors relate the hydrodynamic volume to the molar mass <strong>of</strong><br />

lignin. The MALDI-TOF-MS <strong>and</strong> ESI/MS detectors give absolute molar masses by<br />

mass spectrometry <strong>of</strong> fractions obtained during SEC <strong>of</strong> lignins.<br />

Some recent applications <strong>of</strong> known SEC systems using different types for<br />

mesurements <strong>of</strong> MMs <strong>and</strong> MMDs for lignins <strong>of</strong> different origin will be presented.<br />

© 2004 by Marcel Dekker, Inc.

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