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Handbook of Size Exclusion Chromatography and Related ...

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Figure 2 Configuration <strong>of</strong> an SEC separation with MALS.<br />

detectormaybeusedtodetermineconcentration.Forvarioustypes<strong>of</strong>copolymers,<br />

especially conjugated proteins, both UV <strong>and</strong> DRI detectors are <strong>of</strong>ten used in<br />

combination (see Sec. 6, below).<br />

Preparation <strong>of</strong> the mobile phase for light scattering is atask too <strong>of</strong>ten<br />

neglected. Not only can the presence <strong>of</strong> dust affect the quality <strong>of</strong> recorded signals<br />

<strong>and</strong> the precision <strong>of</strong> the masses <strong>and</strong> sizes extracted from such measurements, but<br />

verysmallsignalsfromminorcomponents<strong>of</strong>thesampleare<strong>of</strong>tenlostifthenoise<br />

levelsare toogreat. Thereare three major sources<strong>of</strong> noise (apart from theusually<br />

very small contributions from the photometer’selectronics): the columns, the<br />

mobile phase, <strong>and</strong> the sample itself.<br />

Because <strong>of</strong> their high sensitivity to dust <strong>and</strong> aggregates, MALS detectors<br />

provide an excellent measure <strong>of</strong> column quality.Deteriorating columns are <strong>of</strong>ten<br />

first noticed by means <strong>of</strong> the detection <strong>of</strong> particulate materials shed by the<br />

columns.Nevertheless,bythejudicioususe<strong>of</strong>appropriatecollections<strong>of</strong>tware,the<br />

life times <strong>of</strong> such deteriorating columns may <strong>of</strong>ten be extended by means <strong>of</strong><br />

suitable statistical analyses (see section on s<strong>of</strong>tware, below). The larger the shed<br />

particles, the more pronounced is their forward scattering.<br />

© 2004 by Marcel Dekker, Inc.

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