Justification of Statistical Overlap Theory in Programmed Temperature Gas Chromatography: Thermodynamic Origin of Random Distribution of Retention Times

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• 作者：Joe M. Davis ; Matevz Pompe ; and Clint Samuel
• 刊名：Analytical Chemistry
• 出版年：2000
• 出版时间：November 15, 2000
• 年：2000
• 卷：72
• 期：22
• 页码：5700 - 5713
• 全文大小：231K
• 年卷期：v.72,no.22(November 15, 2000)
• ISSN：1520-6882

文摘

A specific distribution of compounds' standard-statechanges of enthalpy and entropy between mobile andstationary phases in programmed temperature gas chromatography (PTGC) is shown to produce the Poissondistribution of retention times often postulated in statistical-overlap theory (SOT). A three-part model is proposed,in which the enthalpy change is Poisson distributed, theaverage entropy change depends on the enthalpy change,and the actual entropy change varies in a uniformlyrandom manner about the average entropy change. To testthe model, the entropy and enthalpy changes of 350aliphatic and aromatic hydrocarbons in petroleum werecalculated with commercial GC software. These changesare shown to follow the three-part model. The model thenwas used with Monte Carlo methods to mimic the enthalpyand entropy changes. The substitution of the mimickedenthalpy and entropy changes into an equation for theretention temperature in PTGC is shown to produce aPoisson distribution of retention times that is statisticallysignificant. This finding establishes a scientific link between the thermodynamics governing retention in PTGCand the superficially ad hoc assumption of the Poissonretention time distribution in SOT. Similar thermodynamic distributions are found for flavors and fragrancesand for tetrachlorodibenzo-p-dioxins and furans, whichfollow SOT based on the Poisson distribution, but not forpolychloronaphthalenes, which do not follow that SOT.