Although highly abundant (75.8%), 35Cl as a diagnostic nucleus in solution state NMR is generally not useful due to fast quadrupolar relaxation (I=3/2). However, a notable exception is the aqueous chloride anion, with its spherically symmetrical environment resulting in greatly increased relaxation time and hence usefully sharp signals.
Here we report our continuing investigation into chloride NMR as a potential quantitative tool. We describe the performance on typical instrumentation, some sample-specific complications and potential workarounds, and compare its performance to 1H QNMR of several water soluble chloride salts found in over the counter medicines.