Nuclear magnetic resonance chemical shifts of potassium ions (39K) on ion exchange resins and in muscle.

Chemical shifts of potassium (39K) were calculated from frequencies of beat patterns measured by a pulsed NMR method. This method indicates large chemical shifts for 3 molar KNO3 and 6 molal KI in good quantitative agreement with the steady state NMR measurements of previous investigators. 39K on two wet ion exchange resins and 39K in fresh muscle show insignificant chemical shifts relative to 0.1 M KCl solution. Previous studies showed marked shortening of NMR relaxation times (T1 and T2) for 39K in ion exchange resins and in muscle compared to free solution. These results seem to indicate that even though potassium on resins and in muscle experiences high electric field gradients, these have relatively little effect on the chemical shift of potassium, which may be correlated with the low pK values of the anionic groups in the resins and muscle.