A comparative study of methods for determining gas hold-up time.

It has been proved mathematically that there exists an identity between the various published methods for determining the hold-up times in gas chromatography. All of these methods are based on the equation: ln t'(R) = ln (t(R) - t(M)) = a + bZ, where t(R), t'(R), and t(M) are retention times, adjusted retention times, and hold-up times, respectively; a and b are coefficients that depend on the experimental conditions, and Z is the numbers of carbon atom of a homologue. So long as there are no errors in the values of the retention times, the hold-up times obtained by different methods based on this equation will be the same. The calculated results of experimental data reported in the literature support the viewpoints presented here.