Abstract
The dependence of parameter S on log k'w in the retention equation log k' = log k'w - S ψ for glycine and taurine conjugated bile acids has been found for the first time to be two parallel lines in reversed-phase high-performance liquid chromatography (RP -HPLC). The difference in parameter log k'w or S between glycine and taurine conjugates has been observed to be a constant, which therefore results in the constant selectivity factor between five different glycine and taurine conjugated bile acids in RP-HPLC.