Validation of SW-846 Test Method 3050C for Acid Digestion of Inorganics Found in Sediment, Sludges, and Soils

Collaborative Efforts to Improve Environmental Monitoring
Poster Presentation

Prepared by K. Gagne, T. Strock
EPA, 2777 Crystal Dr, Arlington, Virginia, 22202, United States


Contact Information: gagne.kristin@epa.gov; 302-883-1795


ABSTRACT

SW-846 Test Method 3050 was first developed in 1986 and has gone through two updates with the current version finalized in 1996. SW-846 Test Method 3050 is not a total digestion but a method that was designed to mobilizes trace metals that typically mobilize in the environment and are not bound to the silicate matrix. The extracts from digestion can subsequently be analyzed by Flame Atomic Absorption Spectrometry (FLAA), Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), or Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The main improvements to 3050B that led the 3050C update include using one preparation digestion for all three instruments as 3050B was developed prior to chloride interference removal technology for the ICP-MS. 3050C includes a secondary HCl addition to improve the solubility and recovery of antimony, barium, lead, and silver was made possible due to modernization of ICP-MS collision cell to effectively remove chloride molecular interferences.
To incorporate this updated method into the SW-846 compendium a multi-laboratory validation study was conducted with 10 labs running one or both determinative methods on ICP-OES and ICP-MS (6010D or 6020B) for 23 analytes, a two-fold increase from 3050B for ICP-MS. Five characterized reference materials of sediment, sludge, and soil were digested by all labs following both versions of this method. Following the determinative analysis all the data was compiled and a validation study report was produced with a multitude of statistical analysis and interpretation to assess precision, bias, and comparability of the two methods. In this work we will present the results of this validation study allowing the streamlined use of ICP-MS and ICP-OES with the same digestion steps while showcasing 3050C’s improvements on specific analytes. This updated method will increase laboratory throughput on these sample types by allowing one generalized digestion method instead of two.