DEVELOPMENT AND VALIDATION OF THE NEW IPA MICROWAVE-ASSISTED BEACH METHOD 3051A

An updated, optimized method has been developed to minimize the chemic al biases and inefficiencies between two EPA SW-846 alternative leach methods, microwave-assisted Method 3051 and open vessel Method 3050B, for the determination of metals in solid samples. The microwave method is more easily transferred and provides more reproducible leach resul ts, mainly from more precise control of the temperature during the ext raction process. Previously, reagent limitations originally placed on Method 3051 did not allow these alternative methods to yield similar r esults for some analytes. This work describes the development and vali dation of EPA Method 3051A, which includes an option to add HCl to imp rove the chemistry of the microwave method, making it comparable to op en vessel Method 3050B. Including HCl provides complexation and stabil ization of some analytes by Cl- species, leading to improved recoverie s. Optimizing the acid combination involved adding either 1, 3, or 5 m L of HCl to 9 mL of HNO3 and performing a series of leaches on standar d reference materials (SRMs). Optimum recoveries are achieved for ''pr oblem'' analytes, such as Ag and Sb, by adding 3 mt of HCl. Recovery o f other metals, such as Cu and Ni, are unaffected. Method validation w as provided by leaching and analysis of SRMs.