VERIFYING APPROPRIATE USE OF A METHOD WITHIN A PERFORMANCE-BASED FRAMEWORK

Regulatory monitoring methods are currently prescribed, by in large, by USEPA. A performance-based approach to methods has been suggested as a better means for ensuring improved water information in a variety of monitoring programs in the U.S. One obstacle to implementing a performance-based approach is identifying laboratory requirements that verify appropriate use of a new or modified method. To address this issue, the national Methods and Data Comparability Board coordinated seven laboratories (federal, state, and private entities) that generated data using both the currently approved chemical oxygen demand (COD) method and a new COD method that does not include the use of hazardous chemicals. Results were subjected to two approaches: (a) comparability of the new method to measurement quality objectives (MQO), and (b) comparability of new method data to approved method data. Results of this pilot indicated that most labs could obtain reasonable data using laboratory reagent water but performance was poorer for both methods using actual effluent samples. Several labs could meet the target MQOs using the approved (reference) method but only one lab met the MQOs using the new method. Different labs had acceptable results depending on the type of comparability approach examined. For some labs, the reference method approach could yield a false sense of acceptable method performance. We observed that the use of sample matrix spikes is critical to achieving accurate performance information, regardless of the comparability approach used, and that laboratory verification of a method can be achieved with reasonable effort.