Sample Preparation and Measurement of Losses in Electron Optical Analyses of Particulates in Air and Water Samples

Abstract

Electron optical analyses of the type and concentration of particles in air and water samples utilize some method of transferring the particulate material from the collection media to a transmission electron microscope (TEM) grid. The method used represents a significant step in sample preparation and may be the factor limiting the ultimate reliability of the data. We have found that a carbon replication technique in which the collection media (usually a membrane filter) is carbon-coated directly results in no measurable loss during the transfer. The salient features of the technique and a method for direct observation of any losses are described below.Under normal circumstances the sample received at the Electron Microscope laboratory consists of a membrane filter on which particulates have been deposited. This sample, if lightly loaded, may be prepared in the as-received condition.