Examples Showing the Utility of Doping Experiments in ¹H NMR Analysis of Mixtures

Here we provide examples that demonstrate the value of using properly designed and easily performed doping experiments to give insights about the nature of the analyte(s) present in a ¹H NMR sample. Two mixtures, the first quite complex and the second far less so, have been chosen: (i) the crude pyrolysate from reaction of butyric acid in (supercritical) water at 600 °C and (ii) a mixture of two basic amines. In the former, 13 distinct carbonyl-containing compounds, ranging in relative concentration of nearly 2 orders of magnitude, were positively identified. The latter highlights the advantage of using a doping experiment as opposed to merely comparing the spectra from two separate samples containing the same analyte.