We now turn from visible to UV wavelengths, as most organic and biomolecules do not absorb at visible wavelengths, but only in the UV. To illustrate a potential practical application of UV/Vis-DOSY, we use it to disentangle the UV absorption spectrum of a mixed solution containing two important components of coffee: caffeine and chlorogenic acid (CGA). Knowing the concentrations of these two compounds in coffee is important for various purposes, such as assessing coffee quality and investigating its impact on consumer health, and several analytical methods are commonly used to quantify them. A particularly simple method for determining the concentrations of caffeine and CGA in coffee is UV absorption spectrometry, which makes use of the fact that caffeine and CGA are the main two compounds in coffee that absorb in the UV. However, their UV absorption bands are broad and overlap strongly, which complicates the analysis of the UV spectrum. Since caffeine and CGA have different sizes (see Fig. for their chemical structures), with UV/Vis-DOSY the individual contributions of caffeine and CGA to the UV absorption spectrum can be easily separated.