Enrichment of Amino Acids by Ultrasonic Atomization

Dilute aqueous solutions of two amino acids, tryptophan (Trp) and phenylaramine (Phe), were atomized ultrasonically, and it was found that the amino acids were enriched in the collected mist droplets. The enrichment ratio increased with decreasing initial concentration of amino acids. An enrichment model was proposed and was verified with experimental results. The mechanism is analogous to that of nonfoaming adsorptive bubble separation (NFBS) reported previously. The model explained well the experimental results, and the specific surface area of the mist droplets was estimated. In the case of ultrasonic atomization, the estimated specific surface areas for both Trp and Phe were larger than those of NFBS. This suggests that smaller droplets will be formed by ultrasonic atomization. The present method will be available to separate gas−liquid interfaces where surface-active substances adsorb and to enrich them from dilute aqueous solution.