Setting the Scale: Efficiency of Indirect Referencing in Solid-State NMR Spectroscopy

The benefits of indirect referencing in solid-state nuclear magnetic resonance (SSNMR) spectroscopy are discussed. The technique, routinely used in solution NMR studies, is rarely applied by SSNMR spectroscopists. The benefits of the indirect referencing approach in many SSNMR applications are discussed. In particular, the methods by which indirect methods improve efficiency, reproducibility and help avoid misassignments of chemical shifts are shown. Measurements via direct and indirect methods of a representative sampling of the NMR periodic table are presented to demonstrate the viability of the indirect approach. While any sample with a known chemical shift may be used for indirect referencing, adamantane is demonstrated to be a particularly well-suited solid sample.