Combined solvent- and non-uniform temperature-programmed gradient liquid chromatography. I - A theoretical investigation.
An new class of gradient liquid chromatography (GLC) is proposed and its performance is analyzed from a theoretical viewpoint. During the course of such gradients, both the solvent strength and the column temperature are simultaneously changed in time and space. The solvent and temperature gradients propagate along the chromatographic column at their own and independent linear velocity. This class of gradient is called combined solvent- and temperature-programmed gradient liquid chromatography (CST-GLC). The general expressions of the retention time, retention factor, and of the temporal peak width of the analytes at elution in CST-GLC are derived for linear solvent strength (LSS) retention models, modified van't Hoff retention behavior, linear and non-distorted solvent gradients, and for linear temperature gradients. In these conditions, the theory predicts that CST-GLC is equivalent to a unique and apparent dynamic solvent gradient. The apparent solvent gradient steepness is the sum of the solvent and temperature steepness. The apparent solvent linear velocity is the reciprocal of the steepness-averaged sum of the reciprocal of the actual solvent and temperature linear velocities. The advantage of CST-GLC over conventional GLC is demonstrated for the resolution of protein digests (peptide mapping) when applying smooth, retained, and linear acetonitrile gradients in combination with a linear temperature gradient (from 20°C to 90°C) using 300μm×150mm capillary columns packed with sub-2 μm particles. The benefit of CST-GLC is demonstrated when the temperature gradient propagates at the same velocity as the chromatographic speed. The experimental proof-of-concept for the realization of temperature ramps propagating at a finite and constant linear velocity is also briefly described.
Waters Corporation, Instrument/Core Research/Fundamental, Milford, MA 01757, USA. Electronic address: Fabrice_Gritti@waters.com.
Fabrice
F
Gritti
D000097:Acetonitriles / Q000737:chemistry; D002853:Chromatography, Liquid / Q000379:methods*; D010449:Peptide Mapping; D012997:Solvents / Q000737:chemistry*; D013696:Temperature
D000097:Acetonitriles; D012997:Solvents; C032159:acetonitrile
Band compression factor; Combined solvent- and temperature-programmed gradient liquid chromatography; Gradient peak width; Gradient retention time; Peak capacity per unit time