This expresses the number of peaks which can be resolved in a given part of the chromatogram between the peaks of two consecutive n-alkanes with \(z\) and (\(z+1\)) carbon atoms in their molecules: \[\rm{SN} = \frac{t_{\rm{R}\left(z\,+\,1\right)}- t_{\rm{R}z}}{w_{\rm{h}z}\,+\,w_{\rm{h}\left(z+1\right)}} - 1\] In the German literature the symbol \(\rm{TZ}\) (trennzahl) is commonly used to express the separation number. As the separation number depends on the n-alkanes used for the calculation, they always must be specified with any given \(\rm{SN}\) value.