Accelerating Separations through Efficiency Improvement of Stationary Phases

Accelerating Separations through Efficiency Improvement of Stationary Phases 

We have learned in the previous section that the often neglected increase in temperature has a fundamental potential for reducing analysis times, but we also identified the limitations. Using equivalent plate number as a comparator, the use of temperature caimot realistically reduce analysis times by more than a factor of 2. This section addresses the much more common approach to reducing analysis times by improvements in the column performance. The theoretical foundation will primarily be the dependence of the van Deemter curve shapes on the stationary phase particle diameter dp. Later, we also briefly discuss the potential of superficially porous and monolithic stationary phase materials. 

1 Systematic Speed-Up by Optimization of Particle Diameter and Column Length 

1) The plate height H at the minimum of the curve decreases systematically with decreasing particle diameter dp. This allows improving separation efficiency by reducing dp at constant column length. 

2) The optimal linear velocity ( r-value of the curve minimum) systematically shifts to higher linear velocity with decreasing dp. This automatically speeds up the separation when the linear velocity is correctly adapted to a decreased particle diameter. 

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