Hydroxylamine is commonly employed in laboratory chemistry as a reducing agent, such as for reduction of Cu(II) to Cu(I), yet a sulfate salt oxidizes copper during chemical mechanical planarization (CMP) processing employed in the manufacture of semiconductors. Electrochemical, Fourier transform infrared, and electron paramagnetic resonance measurements were conducted to verify formation of a nitrosyl radical complex, similar to Fremy's salt, that is believed to be the molecular species responsible for catalytic copper oxidation during CMP processing. (C) 2003 The Electrochemical Society.