A convenient method for routine estimation of dead time in gas chromatography.

A set of retention times (tR) of n-alkanes at different temperatures and the primary dead times (tM) are used to determine the 4 numerical constants (a, b, c, and d) of an equation. This equation is rearranged into a second equation, used in turn for routine calculation of the secondary dead time (tMS) of each chromatogram from any member of the n-alkane series. Equation 2 can be used to calculate the tMS of both packed and capillary columns. The calculated tMS values are in good agreement with those of the tM values. The greatest difference is 3.38%, but it is speculated that the percent difference would be lower when more tR data are collected for the determination of the 4 numerical constants of Equation 1. Error in measurement of retention time undoubtedly would affect the accuracy of the estimated dead time, but it is attenuated by a factor of 1 + e(a + bN + c/T + dN/T).