Realization of 1 × 10.6 Theoretical Plates in Liquid Chromatography Using Very Long Pillar Array Columns

We report on the possibility to achieve ultra high efficiencies (order of 1 million theoretical plates) in liquid chromatography in a relatively short time of 20 min (elution time of unretained marker). This was achieved using a micropillar array column with optimized pillar diameter (5 μm) and interpillar distance (2.5 μm) to operate close to the Knox and Saleem limit of micropillar array columns in the region of the 1 million theoretical plate mark under the prevailing pressure restriction (350 bar in the present study). The obtained efficiency was slightly affected (some 15 to 20% around the optimal flow rate) by the turns that were inevitably needed to arrange a 3 m long column on a 4 in. silicon wafer.