The great versatility of Au catalysis has been shown in applications including the selective oxidation of hydrocarbons and alcohols and the direct formation of hydrogen peroxide. However, most interest has focussed on the oxidation of carbon monoxide (CO) for which supported gold nanoclusters are the catalyst of choice. The Cardiff group have recently developed an iron oxide supported gold catalyst for CO oxidation that, remarkably, is active at room temperature and pressure. Investigations of the catalyst have shown that small quantities of water are essential for its operation, but the mechanism is unclear. The need for water implicates that O¿H groups are involved in the catalysis at some stage. INS spectroscopy on MAPS is readily able to observe O¿H stretch and bend modes. It is proposed to observe the effect of water on the catalyst surface and then to follow CO oxidation in situ.