The assay of copper in zinc matrixes by reactor activation analysis presents significant difficulties, since the practicable capture reactions, 63Cu(n,γ)64Cu and 65Cu(n,γ)66Cu, are interfered by 64Zn(n,p)64Cu and 66Zn(n,p)66Cu reactions, as dominant activities. Taking into account this fact, the possibility of developing a method for copper determination in zinc compounds based on the measurement of 66Cu/64Cu activity ratios is discussed. The theoretical fundamentals are formulated; the experimental application for the application to the control of zinc compounds destined to the production of 64Cu is described.