Solvent dependence, as well as other sample conditions like concentration, temperature, and pH (NMR microenvironment) often subtly change the resonance frequencies, further complicating the analysis of the NMR spectrum. This explains why identical J coupling networks of molecules produce NMR spectra of different overall shapes when evaluated under different solution conditions (solvents, temperature, pH) or at different magnetic fields -despite originating from (supposedly) identical molecular frameworks. However, the good news is that the J coupling network of a molecule is relatively highly conserved and much less variable than its chemical shift pattern.