The separation efficiency of different chemical species through HPLC is dependent on myriad variables, including chemical properties of the column, the solvent, the operational temperature, and column dimensions. It is common for some chemical species to co-elute in a given experimental configuration. For example, the sugar lactose [Figure (A, blue)] and inorganic ion phosphate [Figure (A, purple)] have almost identical elution times on a Rezex Organic Acid H + 8% column with a 2.5 mM H 2 SO 4 mobile phase, resulting in a convolution which can be mistaken for a single peak [Figure (A, dashed line)]. As a consequence, these signals would be classified as inseparable using other HPLC data analysis programs and further experimental optimization would be needed to resolve them.