LowCOST‐HSQC Variants for Fast‐Pulsing High ω1‐Resolved 2D Experiments

The LowCOST‐HSQC is a sensitivity‐enhanced HSQC version that retains unused proton polarization for subsequent scans in correlations to low natural abundance nuclei like C or N. Together with fast polarization distribution via isotropic mixing, it allows the acquisition of fast‐pulsing 2D experiments. We give a detailed introduction and comparison of three possible INEPT‐type transfer elements for the LowCOST approach—the original LowCOST, the ZIP, and a specific TIG‐BIRD element—and evaluate various variants of the LowCOST‐HSQC.