Validation of a Microwave Digestion Method for Solid Wastes

Abstract

The techniques that are typically used to prepare RCRA wastes for analysis for metals and other elements are generally relatively time consuming, requiring several hours to several days to complete. They also often involve the use of acid digestions and thermal decomposition steps which may result in analyte losses, incomplete recoveries, or sample contamination. These limitations are well known to the analytical community and to the end users of these data in the U.S. EPA, States, and industry. The resulting inefficiency of these techniques reduces laboratory sample throughput, drives up the cost of analytical testing and impedes decisionmaking. Given these concerns, the OSW Methods Section is interested in developing cost-effective sample preparation techniques for metals and other elements in environmental and process waste samples. Once developed, these techniques can then be written as methods for inclusion in the U.S. EPA “Test Methods for Evaluation of Solid Waste” (SW-846) [1] and made available to the user community. A microwave-assisted sample preparation method for determining elements in solid waste has been developed (Method 3051). This paper reports on the validation of this method by a collaborative study to determine its precision and accuracy. Both qualitative and quantitative aspects of the method were assessed. Qualitative factors evaluated were ease of use and time requirements. Quantitative factors evaluated were the bias and the precision (single laboratory and total). The method was compared with U.S. EPA Method 3050, an open-vessel, hot plate digestion method.

Optimized microwave preparation procedure for the elemental analysis of aquatic sediment

“…[3,4]. There have also been reports on the application of microwave digestion for aquatic sediments [6][7][8][9][10][11][12][13][14][15].…”

“…There have also been reports on the application of microwave digestion for aquatic sediments [6][7][8][9][10][11][12][13][14][15]. They mainly focused on two categories: One was on the comparison between traditional digestion methods and the microwave preparation to prove the advantages of the new technique [4,5]. The other one was on direct microwave digestion experiments with standard reference materials in searching for the optimal preparation procedure [6][7][8][9][10][11][12][13][14][15].…”

“…Several studies deal with the determination of some species of the elements. There are examples: The EPA 3051 method [4,6] determines the environmentally available species of heavy metals by using 20 ml conc. HNO as dissolution reagent and a microwave digestion time of 10 min under 100% microwave power on about 0.1 g sediment sample.…”