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Optimal heating rate in constant pressure and constant flow gas chromatography
Author(s) -
Merrick Mark,
Blumberg Leonid M.
Publication year - 2021
Publication title -
journal of separation science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.72
H-Index - 102
eISSN - 1615-9314
pISSN - 1615-9306
DOI - 10.1002/jssc.202100506
Subject(s) - dimensionless quantity , constant (computer programming) , volumetric flow rate , gas chromatography , analytical chemistry (journal) , chromatography , reaction rate constant , chemistry , pressure drop , thermodynamics , materials science , mechanics , physics , kinetics , quantum mechanics , computer science , programming language
Optimal heating rate is the one resulting in the shortest analysis time for achieving a required separation performance of a column. The previously recommended default heating rate ( R T,Def ) was optimal for temperature‐programmed gas chromatography analyses in constant pressure mode. It has been shown herein that the same recommendation can be extended to constant flow mode with fixed heating rate ( R T ). The numerical value of R T,Def has been herein rescaled from previous 10∘C /t M(10°C per void time) where t M was measured at 50°C, to 12∘C /t Mwith t M measured at 150°C—a round number in the middle of the gas chromatography temperature range, chosen as a reference temperature for numerical values of all temperature‐dependent gas chromatography parameters. It has been experimentally found based on theory developed herein thatR T , Def = 12∘ C /t Mis optimal for columns with φ = 0.001 ( φ = d f/ d is dimensionless film thickness, d and d f are the column internal diameter and film thickness, respectively) in constant pressure mode and constant flow mode with fixed R T . Theory shows that, for arbitrary φ ,R T , Def = 12 ( 1000 φ ) 0.09∘C /t M . The theory also shows that the fixed R T is optimal for constant pressure mode. In constant flow mode, however, the optimal R T should gradually increase with increasing temperature ( T ). The optimal theoretical curves R T ( T ), different for different flow rates, were found. However, only the optimization of the fixed R T was experimentally evaluated due to limited capability of existing gas chromatography instrumentation and resources. It has been shown that the separation‐time tradeoff in constant pressure mode is slightly better than that in constant flow mode. The experimental data are compiled in the Supporting information.