Merging Open-Tubular and Packed Bed Liquid Chromatography

Experimental and theoretical proof is provided for the fact that a microfabricated packed bed column, which is uniformly filled with radially elongated pillars (REPs), can produce the same separation performance as nonpacked, open-tubular columns. These are generally recognized as the best possible chromatographic column format, offering the highest conceivable separation speed and efficiency. It is also demonstrated both experimentally and theoretically that, as long as pressure is not a limiting factor, the REP column format can even outperform the open-tubular column format, with significant gains in either speed or efficiency proportional to the tortuosity, τ, of the bed. Conducting chromatographic experiments on 4 cm long micromachined packed bed columns filled with radially elongated pillars, separation efficiencies corresponding to N = 160 000 theoretical plates (unretained analytes) and N = 70 000 theoretical plates were achieved, despite the relatively large interpillar distance (2.5 μm).