Based on the molecular topological chemical theory and the atomic characteristics, we introduced a new topological index NPm ( m = 1,2,3 ) based on distance matrix and branch vertex of atoms in a molecule which was proposed by defining equilibrium electronegativity of atoms in the molecule and coloring atoms in molecular graph with equilibrium electronegativity, and quantitative structure - retention relationship (QSRR) between gas chromatography retention indices (RI) of sulfides and NPm and number of path ( P2, P3) were proposed by th...