Dr. A. M. Ure was until recently Head of the Department of Spectochemistry in the Macaulay Institute for Soil Research in Aberdeen, Visiting Lecturer in the Department of Pure and Applied Chemistry in the University of Strathclyde in Glasgow and Consultant to the Bureau Communautaire de Référence (now Standard Measurements and Testing Programme) of the European Community, in the development of methods for the preparation of soil and sediment Reference Materials. Since his retirement he is a Visiting Researcher at Strathclyde Univesity. He holds the degrees of BSc (Hons) Chemistry, PhD and DSc from the universities, respectively, of St. Andrews, Aberdeen and Strathclyde.Dr C. M. Davidson is a Senior Lecturer in analytical chemistry at the University of Strathclyde and leads a research group focussing particularly on the determination of heavy metals and natural radionuclides. She obtained her BSc (Hons) and PhD from the University of Glasgow, and undertook postdoctoral work at the State University of Utrecht, Netherlands, and the Scottish Universities Research and Reactor Centre.