Cyclic band compression in toroidal capillary electrophoresis delivers an unlimited number of theoretical plates with a quadratic growth in time and a constant peak capacity.

Analytical instruments able to provide extremely high sensitivities, separation efficiencies, and peak capacities are important for both applied sciences and basic research. It is even more interesting if this can be achieved within organic, aqueous, and physiological solutions without restricting the operation parameters, such as buffer pH, temperature, ionic strength, and background electrolyte composition. Toroidal capillary electrophoresis offers this potential, as was recently proposed and demonstrated. In this platform, the analytes perform continuous round trips inside a fused-silica capillary having a torus-like shape. In the present work, the equations of the number of plates and peak capacity are deduced when on-column cyclic thermal band compression is applied. They are expressed as a function of the number of turns performed by the analyte, axial length of the toroid, number of microholes (reservoirs), compression factor, number of compression events performed per turn, and applied voltage. It was found that the variances of the bands reach a steady state, regardless of the number of dispersion mechanisms present. Consequently, the number of theoretical plates grows indefinitely as the square of time. The expression of peak capacity shows a well-defined limiting value that remains constant over time.