Cyanocobalamin contains multiple exchangeable amide signals, seen between 6 and 8 ppm (expansion shown in Figure ). The triplet at 8.4 ppm (Figure ) is attributed to the secondary amide. Due to its low exchange rate this signal survives in both the NOESY-presaturation PSYCHE and PSYCHE-iWG spectra, showing as a clear singlet at 8.3 ppm in the latter. As a result of restricted rotation, 12 distinct primary amide signals are observed (highlighted in orange in Figure ). These signals have much faster chemical exchange with the solvent and are therefore saturated by the NOESY-presaturation element (Figures and). WATERGATE solvent suppression is preferable here as it enables retention of signals undergoing chemical exchange, as demonstrated in the PSYCHE-iWG spectra (Fig- and). The primary amide proton signals are largely retained, though some signal loss is inevitable due to transverse relaxation. Because PSYCHE-iWG does not require a long recovery delay for presaturation, it allows more scans to be acquired per unit time than NOESY-presaturation PSYCHE. Setting the initial excitation pulse to the Ernst angle, it is possible to boost the SNR of the resultant PSYCHE-iWG spectrum (see Figure , and Table in the Supporting Information). Atropine eye-drop solution. Many pharmaceuticals are formulated in aqueous solution; the example used here, atropine eye-drops for topical ocular administration, is used for conditions including myopia, cycloplegia, and amblyopia. The formulation contains a large concentration range of molecules including the API, degradation products, impurities, and excipients. NMR analysis, already challenging due to the presence of multiple species with high dynamic range, is further complicated by the intense H2O signal (Figure ). The solvent suppression and ultrahigh resolution offered by the PSYCHE-iWG experiment (Figure ) simplify the identification of API signals and reduce signal overlap, allowing key signals from degradation products to be identified. Combining PSYCHE-iWG with 2D correlation structure elucidation methods (data not shown) enabled characterization of the API and several impurities (Figures and).