1. General information on obtaining a spectrum

1.1 Sample preparation

In solution, it is always very useful to examine two ( ¹ H, ¹³ C) or more nuclei ( ¹⁹ F, ³¹ P, ²⁹ Si...). Structural anomalies present in low concentrations are more easily detected with nuclei of high natural abundance. In general, however, even in dilute solution, the mobility of macromolecular chains is low and, due to the dipole-dipole effect, the lines are broad and the spectral resolution poor. Resonance lines only become sharper if the sample is heated to a sufficiently high temperature.

For swollen gels,...