Copper ion production using zeolite and application to MALDI MS of small molecules

Abstract

CuO nanoparticles (CuO) loaded on zeolite (CuO/HM20) and zeolite whose active sites are substituted by copper (CuM20) have been developed as matrices for laser desorption ionization. CuO/HM20 showed efficient Cu+ production upon laser irradiation. By several spectroscopic results, it was found that CuO interacts with hydroxyl groups in zeolite and the lifetime of electron hole pair becomes long owing to the presence of the zeolite support. In addition, it was also found that water molecules surrounding the CuO play an important role in the Cu2++e → Cu+ reaction on the CuO surface. For CuM20, on the other hand, Cu+ production was not effective, probable because strong binding of Cu2+ with water molecules hindered the desorption of copper ions. These two matrices were applied to the desorption ionization of small molecules (arginine, tyrosine, heptacosan, melamine and creatinine). It was found that CuO/HM20 ionized analyte efficiently and CuM20 had selectivity for Cu+ adduction ionization.