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.
Thermodynamic modeling of comprehensive two dimensional gas chromatography isovolatility curves for second dimension retention indices based analyte identification.
A method to thermodynamically model the alkane isovolatility curves of a comprehensive two dimensional gas chromatography (GC × GC) separation is presented. This method omits all instrument modifications, additional chromatogram collection, or method alterations which typical isovolatility curve generation requires. Provided that the thermodynamic indices of reference alkanes are available, chromatographers only need to specify the GC × GC method parameters of their separation to output the isovolatility curves. The curves can then be used alongside reference retention indices to generate two dimensional retention times for each analyte. Agreement between the modeled and experimental retention times provides a secondary mechanism for compound identification, supporting the results of a mass spectral search. The technique was used to model the retention times of a GC × GC separation of aromatic hydrocarbons, achieving an average first dimension retention time modeling error of 11 s and an average second dimension retention time modeling error of 0.09 s. Retention indices modeled retention times provide a simpler analyte identification procedure compared to conventional two dimensional retention indices matching.
Catalytic removal of tert-butyldimethylsilyl (TBS) ether by PVP-I
Abstract A mild, efficient and rapid protocol the deprotection of alcoholic TBDMS ethers using PVP-1 as catalyst in methanol, the procedure of deprotection of various TBDMS ethers were found to be very convenient, easy work-up, high yielding.