Purpose To measure the longitudinal relaxation time, T1, of 1H present in the sample, while observing non-1H spin-1/2 nuclei. Scope This SOP should be completed after an initial 1D cross-polarization (CP) experiment has been completed, but before further experiments are performed. Upon completion of this SOP, the user will be able to set recycle delays appropriate for the purpose of later experiments, either to maximize signal per unit time, or to ensure quantitative intensities.