Mass Spectrometric Analysis of Synthetic Polymers Using Desorption/Ionization on Porous Silicon (DIOS)

—Optimal Etching Conditions for DIOS Chips—

Abstract

Desorption/ionization on porous silicon (DIOS) is a novel matrix-free variant of laser desorption/ionization (LDI) techniques for mass spectrometry. The DIOS chips are produced by electrochemical etching of silicon wafers under light exposure. In the present report, the optimal conditions, regarding resistivity of silicon wafer, etching current density and etching time, for making DIOS chip with better ionization performance are described. In addition, the DIOS mass spectra of various synthetic polymers including polyethyleneglycol, nonylphenolpolyethoxylate, nonylphenolpolyethoxylatesulfate, polymethylmethacrylate are compared with the matrix-assisted LDI mass spectra.