Comparison of Common Solvent Evaporation Techniques in Organic Analysis

Abstract

Isolation of organic constituents from water frequently involves an extraction with a large volume of organic solvent which must be reduced to achieve the desired sensitivity. Common solvent evaporation technique were evaluated to determine which were acceptable for use in pollutant analysis. Techniques for solvent reduction from 200 to 10 ml (macro) and 8 to 0.2 ml (micro) were evaluated. The macro concentration techniques included Kuderna-Danish (K-D) concentration, rotatory evaporation, evaporation on a hot plate in an Erlenmeyer flask, and heated N blowdown in an Erlenmeyer flask. The micro techniques included micro K-D concentration, N blowdown, and N blowdown with a modified Snyder column. A series of model compounds covering a wide range of boiling points (108-323.degree. C) and polarity were used. Based on recovery efficiency alone, N blowdown was significantly superior to the other macro techniques, but its extreme slowness gave K-D the highest figure of merit. With methylene chloride as the solvent, N blowdown with a column was the superior technique.