Improved accuracy and precision in electrophoretic NMR experiments. Current control and sample cell design

[Display omitted] •Electrophoretic NMR suffers from artifacts because of current across the sample.•Motional artifacts are caused by thermal convection and gas bubble rise.•Simple modifications of the sample cell suppress artifacts and impurity effects.•The modified sample cell requires current-controlled pulses of electric field. Electrophoretic NMR has the capacity to provide unique physico-chemical information but is limited by a variety of experimental artifacts, such as thermal convection and electrolytic products in the sample. Here we present some simple modifications to the experimental hardware and protocol that, in a significant number of cases, can much improve experimental accuracy and precision. We show that one can strongly reduce artifacts in a symmetric sample cell with an appropriate feeding of current and with a porous plug suitably inserted. This latter feature requires that the electric field pulses across the sensitive volume are implemented as current-controlled pulses applied to the sample. Measurements with current-controlled pulses have the additional advantage of not requiring calibration with samples of known electrophoretic mobility.