Characterization of polyethylene glycols and polypropylene glycols by capillary zone electrophoresis and micellar electrokinetic chromatography

• Published in: Journal of Chromatography A 2003-01, Vol.985 (1), p.479-491
• Main Authors: Oudhoff, Kathalijne A., Schoenmakers, Peter J., Kok, Wim Th
• Format: Article
• Language: English
• Subjects: Chromatography, Micellar Electrokinetic Capillary - methods; Electrophoresis, Capillary - methods; Poly(ethylene glycol); Poly(propylene glycol); Polyethylene Glycols - chemistry; Polymers; Polymers - chemistry; Propylene Glycols - chemistry
• ISSN: 0021-9673
• DOI: 10.1016/S0021-9673(02)01469-3

Methods based on capillary zone electrophoresis (CZE) and micellar electrokinetic chromatography (MEKC) have been developed and optimized for the separation of polyethylene glycols (PEGs) and polypropylene glycols (PPGs). To provide for charge and detectability both types of polymeric compounds were derivatized with phthalic anhydride (PhAH) or 1,2,4-benzenetricarboxylic anhydride (BTA) before the separation. Derivatization with BTA yielded more complex electropherograms, due to the occurrence of different isomeric reaction products for every PEG or PPG species. Effective mobilities of the PhAH derivatives were related to the number of monomer units in the polymers in a straightforward way. The CZE method could also be used to determine the monomer-number distribution of random and block PEG–PPG copolymers. For an MEKC analysis the PEGs and PPGs were derivatized with phenyl isocyanate. Oligomers of PEGs could be separated up to molecular masses of 5000, while for the more hydrophobic PPGs oligomeric separation was only accomplished for molecular masses of up to 1500. Due to a strongly different separation mechanism for the PEG and PPG derivatives in the MEKC system, a complete group separation of the two types of polymer molecules could be obtained.