I. INTRODUCTION
Recent years have seen the development of methodology transcending mere application of older techniques that could be applied to the rapid, precise determination of specific components in complex mixtures — usually of biologic origin. The development of ion-selective,1 other than for protons, and enzyme-specific electrodes2 are examples in point. Although the latter has its specific limitations of application, the generality of approach is limited only by miniaturization technology and the sophistication of the chemist/biochemist to attach enzyme molecules to insoluble matrices with retention and stability of biological activity. Solid surface fluorescence methods as developed by Guilbault and co-workers3 are also of recent origin and offer great potential for routine and inexpensive assays in the clinical laboratory.