Laboratory Certification & Low-level Mercury

Wisconsin DNR began recognizing laboratories' low-level mercury capabilities in 1997 in support of the Department's mercury strategy for wastewater permits. With the 2008 revisions to the Laboratory Certification and Registration Code, ch. NR 149, Wis. Adm. Code, specific certification for low-level mercury (in the form of Matrix - Ultra-Low Level Metals Assays - Mercury) is available to laboratories. Prior to September 1, 2008, the WDNR relied on s. NR 149.12(2), Wis. Adm. Code as authority to recognize emerging analytical technologies as a mechanism to approve laboratories to submit compliance data for low-level mercury.

DNR recognizes that it may not be necessary to use the most sensitive technique for all permit-related samples so facilities have some flexibility in selecting a laboratory. It is important to note that holding the requisite certification for low-level mercury is not in itself a guarantee that reported results will be accepted for compliance testing. The WDNR is committed to obtaining quality low-level mercury data, and, in addition to other performanced based criteria, laboratories must be capable of quantifying mercury concentrations at or below 50 ng/L. The ons-ite evaluation process will be used to verify a given laboratory's ability to produce quality mercury data.

Summary

To report low-level mercury results to DNR, laboratories must be certified or registered for the field of testing Aqueous (matrix) - Ultra Low Level Metals Assays (Technology) - Mercury (Analyte) under ch. NR 149 and then demonstrate their ability to meet performance-based criteria established by the Department. Although laboratories have flexibility in the method used, sample results must be quantifiable unless the sample concentration is below the water quality criterion. The laboratory must report results to their detection limit. Laboratories must be able to demonstrate the ability to achieve a detection limit (LOD) of 20 ng/L (0.02 ug/L) or lower to obtain certification. The limit of quantitation (LOQ) must be no greater than 50 ng/L (0.05 ug/L).