Mechanisms of amino acid formation using optical emission spectroscopy

Abstract

Magnetoplasma dynamic arc jet was characterized by optical emission spectroscopy (OES) in order to study the mechanisms of amino acid formation induced by electric discharge. Nitrogen, oxygen, and hydrogen atoms and CN radicals were produced by instantaneously heating a CO–N2–H2O gas mixture to 10 000 K. These plasma species were rapidly cooled to form an amorphous film containing amino acid precursors by directly colliding against a wall of a glass tube. This is a new method of producing amino acid precursors without involving the reaction among hydrogen cyanide (HCN), formaldehyde (H2CO), and ammonia (NH3); HCN, H2CO, and NH3 are generally considered important intermediates in amino acid formation. Spark discharge (SD), which is a typical electric discharge in amino acid synthesis, was also characterized by OES. Only CN radicals were observed in a CO–N2–H2O mixture plasma. These radicals became more stable molecules by colliding against other molecules, and sufficiently cooled molecules were dissolved in water. Although HCN appeared to have been formed by SD, amino acids were not effectively synthesized. Therefore, the high activation and rapid cooling processes should be important for the amino acid formation from a CO–N2–H2O gas mixture.