Separation of Amino Acids by Aqueous Two-Phase Electrophoresis on the Micro-Pillar Chips

A micro-pillar chip is proposed and developed to separate the amino acids, phenylalanine and tryptophan, through the aqueous two-phase system (ATPS). The surface properties of micro-pillars, specifically hydrophobicity and hydrophilicity for separation are also investigated. Because their isoelectric points (pI values) are similar, these amino acids are difficult to separate by general extraction techniques; the ATPS is thus adopted in a micro-system to separate these amino acids and only a few micro liters of sample are required. The results reveal that the various surface properties of micro-pillars distinguish the separation mechanisms and efficiency. When the micro-pillar array is constructed in the ATPS, the separation efficiency is improved. Furthermore, the surface of micro-pillars becomes activated from hydrophobic to hydrophilic, and micro-pillars with a hydrophilic surface increase the separation ability without sample residues. Hence separation is improved on incorporating hydrophilic micro-pillars in the ATPS