Temperature effects chromatographic column efficiency

Temperature This criterion is often underconsidered in the operation of a preparative chromatographic process. Temperature has a direct impact on the adsorption isotherms and modifies the retention of the separated compounds. A significant loss of efficiency can be observed with a radial heterogeneity of the temperature, which will modify the retention of the products. This heterogeneity is linked to a difference between the temperature of the eluent and the temperature of the column body. This is particularly important to consider on small-scale preparative devices (5-10 cm ID columns), the wall effect is less significant for larger columns. 

Fig. 4.3. Effect of temperature on column efficiency for the resolution of fumaric acid. Chromatographic conditions column, Aminex HPX-87 (300x7.8 mm I.D.) Mobile phase, 0.026 M H2SO4 flow rate, 0.6 ml/min. Reproduced from Wood et al. (1980),...

The specific retention volume, a chromatographic property of a given solute of interest, is related to the column temperature such that plots of log Vg versus l/T should yield a straight line whose slope is related to either the heat of vaporization of the solute at infinite dilution or, if u = 1 (if Raoult s Law holds), the heat of vaporization of the pure solute. Studies of column efficiency via a consideration of the effect of on H (N = H/L) have shown that an optimum can be found that minimizes H or maximizes N. The interested reader can refer to the excellent text by Harris and Hapgood on PTGC (60). Hinshaw has offered some additional insights into PTGC (61). 

Figure 4-59. Effect of hexafluorophosphate concentration on analyte retention, peak efficiency, N(ii/2), and tailing factor. Chromatographic conditions Column Zorbax Eclipse XDB-C8. Mobile phase 90% 0.1 v/v% phosphoric acid + xPFe [1-25 mM] 10% acetonitrile flow rate, l.OmL/min temperature, 25°C analyte load, Ijxg wavelength, 254 nm. (Reprinted from reference 153, with permission.)...

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