The most frequently used mode in HPLC. Uses low-polarity packings such as octadecyl- or octylsilane phases bonded to silica or neutral polymeric beads. The mobile phase usually is water or water-miscible organic solvents such as methanol or acetonitrile. Elution usually occurs based on the relative hydrophobicity or lipophilicity of the solutes. The more hydrophobic, the stronger the retention. The greater the water solubility of the analyte, the less it is retained. The technique has many variations in which various mobile-phase additives impart a different selectivity. For example, adding a buffer and a tetraalkylammonium salt to an anion analysis would allow ion-pairing to occur and generate separations that rival those of ion-exchange chromatography. More than 90% of HPLC analysts use reversed-phase chromatography.