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 S. Chattopadhyay1, K. Adams2, T. Strock1, K. Kirkland1
1 - USEPA Office of Land and Emergency Managment, , Washington, DC, 20460, United States
2 - USEPA Reg 10, , Port Orchard, Washington,


Contact Information: chattopadhyay.sandip@epa.gov; 703 347 8943

ABSTRACT

The USEPA’s SW-846 Test Method 3050 is an acid digestion for sediment, sludges, and soils that was initially developed in 1986 and has gone through two updates with the current version finalized in 1996. The SW-846 Test Method 3050 is not a total digestion but a method that was designed to prepare and recover sample containing trace elements that typically mobilize in the environment and are not strongly bound to the sorbent (e.g., aluminosilicate, silicate). The aqueous digests can subsequently be analyzed by Flame Atomic Absorption Spectroscopy (FLAA), Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), or Inductively Coupled Plasma Mass Spectrometry (ICP-MS).

The main improvements to Method 3050B that led to the Method 3050C update include using single digestion pathway for the three analytical instruments. The key changes from 3050B to 3050C inclusion of a single digestion pathway for the three SW-846 determinative methods instead of two-pathway digestion option. Nitric acid (HNO3) (1:1 v/v, 10 mL) and HCl (1:1 v/v, 5 mL) are added together to initiate the digestion, and additional 10 mL concentrated hydrochloric acid is added at the end of the procedure.

This multi-laboratory validation study was conducted with 10 laboratories performing one or both determinative methods on ICP-OES and ICP-MS (6010D or 6020B) for 23 analytes using five well-characterized reference materials of sediment, sludge, and soil. All the selected elements, except Sb, followed 1:1 correlation for average concentration in 3050B and 3050C digests across the reference materials, whether analyzed by 6010D or 6020B. The validation study results were in general comparable to Method 3050B, except for higher recovery of Sb.