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

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

<strong>and</strong> concomitant clogging <strong>of</strong> columns. More importantly, however, it was believed<br />

that the high osmotic pressure <strong>of</strong> a concentrated solution in good solvent, the<br />

driving force <strong>of</strong> segregation by MW, was critical in HOPC (1). Figure 4 shows<br />

examples <strong>of</strong> separation in the good solvent condition. Figure 4a was<br />

obtained in HOPC <strong>of</strong> poly(methyl methacrylate) (Mw ¼ 7:9 10 4 g=mol,<br />

Mw ¼ 4:0 10 4 g=mol, with reference to polystyrene) in tetrahydr<strong>of</strong>uran (3). In<br />

total, 2.1g <strong>of</strong> 25wt% solution was injected at 0.1mL=min into a column <strong>of</strong><br />

3:9 300 mm packed with CPG particles [mean pore diameter 128A ˚ , particle size<br />

200=400 mesh; the surface was modified with trimethylsilanol (TMS) to avoid<br />

possible adsorption <strong>of</strong> the polymer]. The figure shows chromatograms obtained by<br />

<strong>of</strong>f-line SEC (Phenogel, 10 3 ,10 4 , <strong>and</strong> 10 5 A ˚ ; Phenomenex, Torrance, California,<br />

U.S.A.). Each chromatogram is normalized by the peak area above the baseline.<br />

Early fractions collected the high end <strong>of</strong> the MW distribution <strong>of</strong> the original<br />

polymer. With an increasing fraction number, the peak MW shifts lower, <strong>and</strong> the<br />

peak broadens. Late fractions are not much different from the polymer injected.<br />

Another typical separation in a good solvent condition is shown in<br />

Fig. 4b (5). This example is for poly(vinyl pyrrolidone) K30 (Fluka, Buchs,<br />

Switzerl<strong>and</strong>) [Mw ¼ 1:7 10 4 g=mol, Mw ¼ 4:4 10 3 g=mol, with reference to<br />

poly(ethylene glycol)] in water. Then, 2.2g <strong>of</strong> 30wt% solution was injected at<br />

0.1mL=min into a column <strong>of</strong> 3:9 300 mm packed with CPG particles (mean<br />

pore diameter 130A ˚ , particle size 200=400 mesh; CPG was washed with acid) at<br />

room temperature. The figure shows chromatograms obtained by <strong>of</strong>f-line aqueous<br />

Figure 4 Examples <strong>of</strong> HOPC separation in a good solvent. Chromatograms obtained in<br />

<strong>of</strong>f-line SEC are shown for some <strong>of</strong> the fractions. Each chromatogram is normalized by the<br />

peak area above the baseline. The chromatogram for the original polymer is shown as a<br />

dashed line. Fraction numbers are indicated adjacent to each curve. (a) Separation <strong>of</strong><br />

poly(methyl methacrylate) in tetrahydr<strong>of</strong>uran. (b) Separation <strong>of</strong> poly(vinyl pyrrolidone)<br />

K30 in water. (From Refs 3 <strong>and</strong> 5.)<br />

© 2004 by Marcel Dekker, Inc.

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

Saved successfully!

Ooh no, something went wrong!