Figure 1. Poppe plots for various liquid chromatography configurations.

A: 2.6 μm particles, 4000 psi, 25 °C. Chromatograms from Jung, et al.⁹ and related unpublished work with 2.6 μm particles were used to establish an estimate of the “C term” which is the most important term for high-speed work. The dimensionless C term, which includes a contribution from the postcolumn reactor, was determined to be 0.22. Typical values of 2 and 1.5 for B and A respectively were used. These values represent data for 1.7 μm particles well. In order to determine Poppe plots with new conditions we used published equations and temperature dependence of viscosity²⁰ B: 2.6 μm particles, 7000 psi, 25 °C, C: 1.7 μm particles, 7000 psi, 25 °C, D: 1.7 μm particles, 7000 psi, 70 °C. Here, N is the number of theoretical plates, t₀ is the dead time for unretained analytes, and t₀/N is plate time. Separation conditions that overlap with the desired separation time for serotonin<1 min, corresponding to t₀<7.5 s, and that are accessible are denoted by the hatched blue area.