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Handbook of Size Exclusion Chromatography and Related ...

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100–1358C (3,4). Later investigations have shown that meta-cresol can cause<br />

degradation <strong>of</strong> PET through acid-catalysed hydrolysis (5). For this reason a<br />

mixture <strong>of</strong> nitrobenzene-tetrachloroethane was developed as a solvent for PET<br />

analysis at room temperature (5). The following eluent systems have also been<br />

developed successfully: ortho-chlorphenol/chlorform (25/75, v/v) for GPC at<br />

room temperature (6), ortho-chlorphenol (8), 1,1,2,2-tetrachloroethane/phenol (9)<br />

<strong>and</strong> methylene chloride/dichloroacetic acid (10).<br />

Later 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) was developed to carry out<br />

successful GPC analysis <strong>of</strong> PET at room temperature (11). This method has the<br />

disadvantage <strong>of</strong> being very expensive. As a consequence, mixtures <strong>of</strong> HFIP with<br />

less expensive solvents were developed. Mixtures <strong>of</strong> methylene chloride/HFIP<br />

(12) <strong>and</strong> chlor<strong>of</strong>orm/HFIP (e.g., 98/2, v/v) allow GPC analysis at room<br />

temperature (13–15).<br />

3.2 Polyamides<br />

Polyamides such as nylon have been investigated in HFIP containing 0.05 M<br />

potassium or sodium trifluoroacetate (16,17). This highly polar eluent is needed in<br />

order to interact with the very polar amide groups in polyamides. Sodium<br />

trifluoroacetate destroys the intermolecular hydrogen bonding between the amide<br />

groups, thus single polymers appear as single molecules <strong>and</strong> not as polymeric<br />

associations.<br />

3.3 Fluoropolymers<br />

GPC methods for fluoropolymers are known. In particular, perfluoroether or<br />

polymers containing fluorinated side chains have been the subject <strong>of</strong> literaturedescribed<br />

investigations. They were performed in special partly fluorinated eluents<br />

or in DMAc (18). For a successful GPC analysis <strong>of</strong> this very special polymer group<br />

a detailed investigation on structure <strong>and</strong> solubility is recommended.<br />

4 GPC METHODS USED AT POLYMER STANDARDS SERVICE<br />

Polyester <strong>and</strong> polyamide GPC analyzes are typically performed using HFIP<br />

containing 0.05 M potassium or sodium trifluoroacetate. The st<strong>and</strong>ard column<br />

combinations for these analyzes are the highly resistant PerFluoroGel (PFG)<br />

columns: PSS-PFG 100 A ˚ , 7 mm, 8 300 mm þ PFG 1000 A ˚ , 7 mm<br />

8 300 mm. Alternatively a combination <strong>of</strong> 2 PFG linXL, 7 mm, 8 300 mm<br />

is used. This system covers the full range <strong>of</strong> molecular weights <strong>of</strong> polycondensates<br />

<strong>and</strong> allows the analysis <strong>of</strong> oligomers up to 1 or 2 Mio D. The calibration <strong>of</strong> this<br />

system with PMMA st<strong>and</strong>ards allows the determination <strong>of</strong> the relative molecular<br />

weight <strong>of</strong> the analytes. The viscosity or light-scattering coupling allows the<br />

© 2004 by Marcel Dekker, Inc.

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