Robust estimation of thermodynamic parameters (ΔH, ΔS and ΔCp) for prediction of retention time in gas chromatography – Part I (Theoretical)

• Published in: Journal of Chromatography A 2015-12, Vol.1425, p.249-257
• Main Authors: Claumann, Carlos Alberto, Wüst Zibetti, André, Bolzan, Ariovaldo, Machado, Ricardo A.F., Pinto, Leonel Teixeira
• Format: Article
• Language: English
• Subjects: Gas chromatography; Initialization method; Optimization; Parameter estimation; Retention time; Thermodynamic properties
• ISSN: 0021-9673
• DOI: 10.1016/j.chroma.2015.10.072

•The approximation error problems of parameter estimation in GC have three well defined regions.•An algorithm was developed to discriminate the different regions of the surface of the approximation error function.•The routine developed in this work can be used as robust initialization in estimating parameters (ΔH, ΔS, ΔCp). An approach that is commonly used for calculating the retention time of a compound in GC departs from the thermodynamic properties ΔH, ΔS and ΔCp of phase change (from mobile to stationary). Such properties can be estimated by using experimental retention time data, which results in a non-linear regression problem for non-isothermal temperature programs. As shown in this work, the surface of the objective function (approximation error criterion) on the basis of thermodynamic parameters can be divided into three clearly defined regions, and solely in one of them there is a possibility for the global optimum to be found. The main contribution of this study was the development of an algorithm that distinguishes the different regions of the error surface and its use in the robust initialization of the estimation of parameters ΔH, ΔS and ΔCp.