TEMPERATURE GRADIENT CHROMATOGRAPHY

Kaiser, R. Temperature gradient chromatography. 1. Reversions gas chromatography. Chromatographia 1, 199(1968). 

The practices of isocratic and gradient sorptive chromatography are very different. Isocratic chromatography tends to be very sensitive to the details of mobile phase preparation, temperature, pump speed, and sample composition. Gradient chromatography is usually more tolerant of small variations in these factors but may be extremely sensitive to column history, equilibration time, and gradient preparation. 

Renn, C. N. and Synovec, R. E., Refractive index gradient detection of biopolymers separated by high-temperature liquid chromatography, /. Chromatogr., 536, 289, 1991. 

Figure 9.23 Separation of equimolar concentrations of methylglycosides by gas-liquid chromatography. The analysis was performed on an OV-1 stationary phase using a temperature gradient from 120 to 220 °C.

Most recently, a further study has been performed using superheated-water HPLC with NMR and MS to analyse a mixture of sulphonamides [68]. The chromatography was performed as before with D20-phosphate buffer (pD 3.0) as eluent. A temperature gradient from 160 to 200 °C at 2°C min-1 was employed. A mixture of four sulphonamides, i.e. sulacetamide, sulphadiazine, sulfamerazine and sulfamethazine, was separated in this system with UV, NMR and MS detection. It rapidly became clear from a study of the spectroscopic data that while sulfacetamide and sulfadiazine gave the expected NMR and mass spectra, those for sulfamerazine and sulfamethazine did not. These compounds gave spectra that were 3 and 6 mass units higher than expected,... 

The given description of the gas phase transport in a tube with a temperature gradient is only valid for adsorption equilibria of reversible mobile adsorptions without any superimposed chemical reaction. The temperature profile along the chromatography column is approximated to be linear by ... 

The model of ideal linear gas chromatography (Equation 1) [12] also describes the transport of a chemical species in the temperature gradient of a vacuum tube. At molecular flow conditions the linear velocity of the carrier gas, which is identical to the transport velocity of the adsorbate in the gas phase, has to be substituted by the fraction of the column length over the average retention time of the species in the column ... 

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