Retention index calculation using Kovats constant model for linear temperature-programmed gas chromatography

Retention data from n-alkane series were obtained on polar and non-polar capillary columns under different column headpressures and heating rates. In addition to cubic spline polynomials and the equation of Wang-Sun, four models based on the extension of the Kovats equation were tested for direct interpolation of retention index. The quadratic temperature Kovats constant (QTKC) model and cubic spline functions were predictively comparable and provided the most accurate and stable results for the C-7-C-22 alkane range. The QTKC model is simpler to apply than splines and the parameters to estimate are already known.