Sprayed microdroplets: methods and applications

Abstract

Electron probe X-ray microanalysis (EPXMA) is capable of yielding quantitative data from excited specimen volumes < 1 μm3. Thus, the analysis of fluid microvolumes in the range 10−11 to 10−10 litres is comfortably within the scope of this technique. For this reason, EPXMA was advocated at an early stage in its technological evolution for the analysis of nanolitre fluid volumes (Ingram & Hogben, 1967). Subsequently a number of laboratories have independently pursued physiological questions by the analyses of diverse biological fluids. This family of related microdroplet methods is described fully elsewhere in this volume by Roinel and Rouffignac (Chapter 11). However, in order that the sprayed microdroplet technique be seen in a realistic perspective a brief resumé of the more conventional ‘direct deposition’ microdroplet methods is provided here.