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.