Broadband APT (BAPT): a Versatile APT Experiment with Improved J-Compensation and Optimal Suppression of Artifacts in Cq-only Spectra

A modified version of the CAPT (Compensated APT) experiments, the Broadband-APT (BAPT) sequence is proposed, that allows the user to record APT- and Cq-only spectra in a simple manner and that improves both the tolerance for wide ranges of 1JCH values in the APT spectra and the suppression of residual CHn signals in the Cq-only spectra. Compared to the original version with delays d1, of equal lengths, these improvements can be achieved with three different delays d1, d2, and d3, which can be set for three different one-bond coupling constants. The recording of APT and Cq-only spectra is governed most simply by a single constant, which adjusts the delay d2 and the phase programs for the two proton 90° pulses accordingly. These attributes make this experiment attractive for 13C analysis of small molecules, including spectral editing, particularly in high-throughput analysis laboratories.