Sample Preparation for Environmental Analysis in Solids (Soils, Sediments, and Sludges)
Environment: Water and Waste
Published Online: 15 SEP 2006
Copyright © 2000 John Wiley & Sons, Ltd. All rights reserved.
Encyclopedia of Analytical Chemistry
How to Cite
Kimbrough, D. E. 2006. Sample Preparation for Environmental Analysis in Solids (Soils, Sediments, and Sludges). Encyclopedia of Analytical Chemistry. .
- Published Online: 15 SEP 2006
The purpose of the analysis of environmental contaminants, such as pesticides, organic solvents, and toxic elements, in solids is to provide the basis for certain environmental decisions. Thus, the needs of the end user of the analytical procedures are the guide to understanding sample preparation. Two common goals for end users are regulatory compliance and data comparability, which is why it is very common to use standardized analytical procedures. There are two steps in the analysis of solids, the separation of analytes of interest from the rest of the sample and then the instrumental analysis of the analytes. The first step is the topic of this article. More than any other medium, solids are subject to severe matrix effects. The sample matrix is the portion of the sample not of interest except to the extent it affects the analysis of the portion that is of interest. Matrix effects can include reactions that prevent the separation of the analytes from the sample matrix or the inclusion of nontarget materials that interfere with the instrumental analysis. Other issues with sample matrix include heterogeneity and moisture content. A heterogeneous sample can give unrepresentative results and the moisture content can change over time and lead to variable results. These issues are often dealt with by drying and homogenization. The two most common types of analyte that require sample preparation are elements (e.g. copper and lead) and nonvolatile organic compound (NOC) (e.g. pesticides and polychlorinated biphenyls (PCBs)). Acid digestion is the most common sample preparation for elemental analysis. The acid must be aggressive enough to break the bonds between the analyte and the matrix and it must yield a form of the element soluble in the acid. NOCs are generally extracted from the sample matrix by organic solvents. The extraction solvent must be more soluble to the analyte than the sample matrix and the solvent must be able to penetrate into the sample matrix in order to solubilize the analyte. Thus the correct selection of acids and extraction solvents is the key to successful extraction