A simple, fast, and accurate thermodynamic-based approach for transfer and prediction of GC retention times between columns and instruments Part II: Estimation of target column geometry.
The transfer of thermodynamic parameters governing retention of a molecule in gas chromatography from a reference column to a target column is a difficult problem. Successful transfer demands a mechanism whereby the column geometries of both columns can be determined with high accuracy. This is the second part in a series of three papers. In Part I of this work we introduced a new approach to determine the actual effective geometry of a reference column and thermodynamic-based parameters of a suite of compounds on the column. Part II, presented here, illustrates the rapid estimation of the effective inner diameter (or length) and the effective phase ratio of a target column. The estimation model based on the principle of least squares; a fast Quasi-Newton optimization algorithm was developed to provide adequate computational speed. The model and optimization algorithm were tested and validated using simulated and experimental data. This study, together with the work in Parts I and III, demonstrates a method that improves the transferability of thermodynamic models of gas chromatography retention between gas chromatography columns.
A standardized method for the calibration of thermodynamic data for the prediction of gas chromatographic retention times.
A new method for calibrating thermodynamic data to be used in the prediction of analyte retention times is presented. The method allows thermodynamic data collected on one column to be used in making predictions across columns of the same stationary phase but with varying geometries. This calibration is essential as slight variances in the column inner diameter and stationary phase film thickness between columns or as a column ages will adversely affect the accuracy of predictions. The calibration technique uses a Grob standard mixture along with a Nelder-Mead simplex algorithm and a previously developed model of GC retention times based on a three-parameter thermodynamic model to estimate both inner diameter and stationary phase film thickness. The calibration method is highly successful with the predicted retention times for a set of alkanes, ketones and alcohols having an average error of 1.6s across three columns.
A Preference for Forgetting: Some Reflections on Publishing Looking For Blackfellas' Point: An Australian History of Place
Blackfellas' Point lies on the Towamba River in south-eastern New South Wales. As the river descends rapidly from its source on the Monaro plains, it winds its way through state forest, national park and farming land. Around twenty-five kilometres before it reaches the sea, just south of Eden, it passes through Towamba, the small village in which Mark McKenna now owns eight acres of land. Mark's land looks across the river to 'Blackfellas' Point', once an Aboriginal camping ground and meeting place. Looking for Blackfellas' Point is a history that begins by looking across the river to the arc of bush that is 'Blackfellas' Point. From there, Mark McKenna's gaze pans out - from the history of one place he knows intimately, to the history of one region and, ultimately, to the history of Australia's quest for reconciliation between Indigenous and non-Indigenous Australians. Looking For Blackfellas' Point is a history for every Australian who is interested in the story of settler-Australia's relations with Indigenous people - what happened between us, how we learnt to forget and, finally, how we came to confront the truth about our past and build a movement for reconciliation.