Radio-frequency pulse calibration using the MISSTEC sequence

NMR sequences are composed of multiple radio-frequency pulses. Probe adjustment, sample concentration and solvent influence the loading factor, therefore these parameters also impact the validity of flip angles. The commonly used method to calibrate RF pulses is to measure a nutation curve by varying the pulse duration. However, this method is impacted by off-resonance effects, radiation damping and B₁ and B₀ inhomogeneities. Furthermore, it is important to avoid partial saturation. In this work, the MISSTEC sequence is proposed for pulse calibration. This sequence takes only 8 s or 2 min for ¹H or ¹³C calibration, respectively. High accuracy (with an error below 1%) was obtained for both nuclei. Therefore, the calibrations can be done rapidly and accurately. Furthermore, the MISSTEC measurement could be performed on each sample - in an automated way- before acquisitions, after which the calibration found could be automatically used.