28.02.2013 Views

Handbook of Size Exclusion Chromatography and Related ...

Handbook of Size Exclusion Chromatography and Related ...

Handbook of Size Exclusion Chromatography and Related ...

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

Figure 16 Block scheme <strong>of</strong> a full adsorption–desorption/SEC system. V 2 is sample<br />

injector, FAD <strong>and</strong> SEC are full adsorption–desorption <strong>and</strong> SEC columns, respectively. P#1<br />

<strong>and</strong> P#2 are pumping systems. For further explanation see the text.<br />

8 REMOVAL OF POLYMERIC INTERFERENCES<br />

FROM SAMPLES<br />

Polymeric admixtures <strong>of</strong>ten complicate accurate characterization <strong>of</strong> macromolecular<br />

analytes <strong>of</strong> interest. A typical example represents characterization <strong>of</strong> products<br />

<strong>of</strong> block-, graft-, star-, <strong>and</strong> so on copolymer syntheses <strong>and</strong> also analyses <strong>of</strong><br />

polymers that were chemically transformed by analogous reactions, including<br />

functionalization <strong>and</strong> oxidization processes. Complex polymer systems <strong>of</strong> these<br />

kinds are frequently characterized by conventional SEC, although it is evident that<br />

interfering admixtures can be discriminated in this way only if their molecular sizes<br />

differ substantially from the sizes <strong>of</strong> analyte molecules. Presence <strong>of</strong> admixtures is<br />

<strong>of</strong>ten masked by the chromatographic b<strong>and</strong> broadening phenomena. Macromolecular<br />

admixtures in broad molar mass polymers easily remain undiscovered even<br />

if the size <strong>of</strong> analyte <strong>and</strong> admixture differs by a factor <strong>of</strong> two. Evidently,<br />

conclusions about purity <strong>of</strong> products (for example, about absence <strong>of</strong><br />

homopolymers in statistical-, block-, graft-, <strong>and</strong> miktoarm-copolymers or diblocks<br />

in triblock species <strong>and</strong> vice versa can hardly be drawn from an SEC chromatogram<br />

if a thorough evaluation <strong>of</strong> SEC b<strong>and</strong> broadening is omitted. Unfortunately, many<br />

papers entitled “Synthesis <strong>and</strong> characterization <strong>of</strong> ...” are based on this<br />

© 2004 by Marcel Dekker, Inc.

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!