TEMPERATURE OF THE ELUENT - A NEGLECTED TOOL IN HIGHPERFORMANCE LIQUID-CHROMATOGRAPHY

The influence of eluent temperature on efficiency in high-performance liquid chromatography with special reference to the role of viscous he at dissipation is investigated for water-jacket and air-bath thermosta tted columns. When separations are performed on well-thermostatted lar ge-diameter columns packed with small particles or on analytical colum ns operated at high flow-rates, the additional thermostatting of the e luent to a specific temperature below the column temperature turns out to have some advantages. The precooled eluent causes the development of a temperature profile in a radial direction which is opposed to and compensates the radial temperature profile in the column caused by vi scous heat dissipation. For columns that are thermostatted in an air b ath, a similar effect is observed, but the strong dependence of the co lumn temperature on the eluent temperature results in a poor reproduci bility if the eluent is not thermostatted itself.