Chapter 2 - NMR Applications for Polymer Characterisation

Abstract

Polymers in drugs are widely used as formulation aids and as active ingredients. Because of their polymer structures, conventional chromatographic methods often fail for different reasons and the lack of suitable standards. This chapter deals with the more common liquid nuclear magnetic resonance (NMR) techniques. By means of applied examples of routine analysis a summary is given about the ability and the scope of NMR spectroscopy in polymer analysis. Thus, different chemical types of polymers are distinguished to get a better overview about the wide field of applications. NMR spectroscopy in liquids has been developed to become a tool mainly for chemists and nowadays plays a major role in structure elucidation. Polymer classes such as polydimethyl siloxane (PDMS), polysaccharides, and polyether-, polyethylene glycol (PEG)-, and polypropylene glycol (PPG)-based emulsifiers are analyzed in this chapter. Quantitative analysis is enabled by the use of external and internal standards and correlates well with the documented Fourier transform (FT)/IR (infrared). To obtain a better signal resolution and more detailed spectral information, it is recommended to run NMR spectra at high temperature. Besides its classical domain of qualitative analysis, qNMR is a suitable method to quantify an emulsifier in a drug formulation. Emulsifiers often consist of a basis structure that represents a mixture of similar molecules.