It is well known that chemical shifts can vary with the solvent, pH, temperature, and sample concentration, with differences ranging from <0.1 ppm to >1ppm. For example, the chemical shifts of parthenolide in DMSO-d6 vs. CDCl3 vary by up to 0.22 ppm with a standard deviation of 0.12 ppm (data not shown). Considerably larger effects can be observed, especially for nuclei close to proton donors and acceptors at different pH. This means that chemical shifts are highly reproducible under well-controlled conditions, while posing reproducibility challenges when the exact conditions are not reported and, therefore, cannot be reproduced.