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Handbook of Size Exclusion Chromatography and Related ...

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not savealot <strong>of</strong> time <strong>and</strong> solvent, despite the fact that no distribution information<br />

isavailable.Allmajor producers<strong>of</strong>molar masssensitivedetectorshavepublished<br />

initial results on this technique (4,5). Asummary <strong>of</strong> pros <strong>and</strong> cons is listed in<br />

Table 1.<br />

2.4 High-Speed SEC Columns<br />

PSS investigated the limitations <strong>of</strong> different approaches to reduce time<br />

requirements <strong>and</strong> decided to start aresearch project on fast SEC separations<br />

evaluating <strong>and</strong> quantifying the effects <strong>of</strong> different column dimensions <strong>and</strong><br />

packings (6). The results <strong>of</strong> this work are presented in Sec. 3. The data presented<br />

therewill allowthe reader to underst<strong>and</strong> <strong>and</strong> apply the different principles for fast<br />

SEC separations in their own environment. A summary <strong>of</strong> advantages <strong>and</strong><br />

limitations are given in Table 1.<br />

3 COLUMN DESIGN CONCEPTS FOR HIGH-SPEED SEC<br />

Time requirements for chromatographic separations can be reduced most simply<br />

by changing the column dimensions. This is the easiest adaptation for column<br />

manufacturers, because they will not need to change the chemical <strong>and</strong> or physical<br />

nature <strong>of</strong> the packings. However, chromatographic theory predicts anumber <strong>of</strong><br />

important limitations, which have to be taken into account (7,8).<br />

Alternatively, the packing <strong>of</strong> columns can be optimized for shorter run<br />

times. PSS investigated the efficiency <strong>of</strong> packings with different particle size <strong>and</strong><br />

their potential to increase throughput. Table 2 discusses effects <strong>of</strong> column<br />

parameter modifications <strong>and</strong> summarizes their advantages <strong>and</strong> limitations.<br />

3.1 Quantitative Investigation <strong>of</strong> Ideal Column Dimensions<br />

Identical experimental conditions have been used to compare the results <strong>of</strong><br />

columns with different dimensions in the investigation carried out by PSS. They<br />

used a styrene–divinyl benzene-based column packing with 5 mm particle size<br />

<strong>and</strong> a wide pore size range (PSS SDV 5 mm linear column). A single column was<br />

used in all cases. All experiments were run on the same instrument (to avoid any<br />

influence by the instrument hardware), evaluated with the same s<strong>of</strong>tware (PSS<br />

WinGPC), <strong>and</strong> by a single operator. All experiments were performed with a<br />

polystyrene st<strong>and</strong>ard cocktail containing seven narrow st<strong>and</strong>ards (from 2.5 million<br />

down to 1900 g/mol) in THF as the eluent. Only flow rates <strong>and</strong> injection volumes<br />

were adjusted accordingly.<br />

© 2004 by Marcel Dekker, Inc.

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