Different approaches for determination of the attachment degree of polyethylene glycols to poly(anhydride) nanoparticles.

PURPOSE The aim of the study was to find an appropriate method for determination of the attachment degree of polyethylene glycol (PEG) to poly(anhydride) nanoparticles. METHODS The nanoparticles were modified with hydroxy-functionalized or with amino-functionalized PEGs. Three methods for their determination were applied and examined: in particular colorimetry, nuclear magnetic resonance ( (1) H-NMR), and elemental analysis (EA). RESULTS The attachment degrees determined by (1) H-NMR and colorimetry were similar. The associated amounts of PEGs estimated on the basis of EA differed significantly than those determined by colorimetry and (1) H-NMR. CONCLUSION The colorimetric determination was considered fast and simple technique, but (1) H-NMR contributed to more precise results.