A simple, fast, and accurate thermodynamic-based approach for transfer and prediction of gas chromatography retention times between columns and instruments Part III: Retention time prediction on target column.
This is the third part of a three-part series of papers. In Part I, we presented a method for determining the actual effective geometry of a reference column as well as the thermodynamic-based parameters of a set of probe compounds in an in-house mixture. Part II introduced an approach for estimating the actual effective geometry of a target column by collecting retention data of the same mixture of probe compounds on the target column and using their thermodynamic parameters, acquired on the reference column, as a bridge between both systems. Part III, presented here, demonstrates the retention time transfer and prediction from the reference column to the target column using experimental data for a separate mixture of compounds. To predict the retention time of a new compound, we first estimate its thermodynamic-based parameters on the reference column (using geometric parameters determined previously). The compound's retention time on a second column (of previously determined geometry) is then predicted. The models and the associated optimization algorithms were tested using simulated and experimental data. The accuracy of predicted retention times shows that the proposed approach is simple, fast, and accurate for retention time transfer and prediction between gas chromatography columns.
Mechanistic modeling and CFD simulation of gas chromatography to predict separation processes
Gas chromatography (GC) is a frequently applied separation technique. Nevertheless, a suitable operational setup for reaching separation may require extensive time and resources. Mathematical models have been used to predict chromatographic parameters and to propose the analysis conditions; however, the use of empirical correlations has limited application and may be inaccurate. This work proposed a precise physical-based mathematical model using mechanistic equations to describe GC under constant pressure and constant flow, aiming to predict holdup time and the full separation process in a CFD software. A bidimensional model was validated by the description of the mobile phase flow and compounds elution, allowing to predict the chromatographic parameters in both GC operating modes. The observed errors were less than 5% for all predicted parametric values, which is around the input parameter uncertainty. The 2D approach allowed a relatively quick computational time to describe with high accuracy the evaluated parameters, concentration profile, and an operational setup for separating the compounds.
A study of the local tissue reactions in man to cortisone and compound F. VI. Histopathological studies of the local effect of compound F in normal and pathologic skin of man.
After our previous negative studies (1) of the local effect of cortisone acetate in the skin of man, a year ago, a parallel study of 17-hydroxycorticosterone-21-acetate, Compound F, was outlined. Theoretically, Compound F should be the active steroid. It was so suggested by Rothman (2), that in all probability Compound F and not cortisone would be active locally in the skin of man.