In High-Performance Liquid Chromatography (HPLC) analysis, RRF stands for Relative Response Factor. It is a ratio of the detector response for a target compound to that of a reference compound, typically an internal standard, under identical analytical conditions. The RRF is used to calculate the concentration of the target compound in a sample by comparing its detector response to that of the reference compound. The RRF corrects for differences in the detector response between the target compound and the reference compound due to factors such as differences in their chemical structures, retention times, and detector sensitivity.