Wastewater Standards and Extraction Chemistry in Validation of Microwave-Assisted EPA Method 3015A

The difficulties associated with the control and transfer of environmental leach methods are discussed. Optimized EPA Method 3015A, a microwave-assisted leach of wastewater and drinking water matrices and aqueous extracts, is evaluated. The option to add HCl in addition to HNO3 provides better complexation and recovery of certain metals that are regulated by the Resource Conservation and Recovery Act (RCRA) than the original HNO3-only Method 3015. Also discussed is the preparation and appropriate use of “simulated” wastewater standards. Standard reference materials for a wastewater matrix are unavailable, and this novel approach provides NIST-traceability of results for the first time on this matrix type. Leach concentrations from these “simulated” standards were determined using both the 5 mL HNO3 and the 4 mL HNO3 and 1 mL HCl leach options of new Method 3015A. Validation of the new mixed-acid option of Method 3015A has been provided by evaluating its performance on the 23 elements for which original Method 3015 was validated. In addition, validation is provided for boron, mercury, and strontium, elements that were not validated in original Method 3015. Method 3015A has been developed into a method capable of evaluating 26 elements in a single, efficient, 20-min procedure.