Establishing Acceptable Analytical Methodologies and the Associated Practical Quantitation Limit – A Colorado Regulatory Perspective

An important part of the regulatory process for chemical contaminants, including emerging contaminants, is the establishment of acceptable analytical methodologies for that compound and the determination of a practical quantitation limit (PQL) associated with that method for the compound. In Colorado, this step is undertaken once the compound has been identified as a potential contaminant and a numerical limit has been included in the regulations. The Water Quality Control Division of the Colorado Department of Public Health and Environment relies upon a work group process as a participation mechanism for stakeholders to provide ideas and recommendations on the development of proposed policies and guidance documents. In 2004, the Division established a PQL Work Group to obtain stakeholder input to the development of a guidance document for use in the determination of PQLs for regulated compounds. The draft guidance document was presented to the public at a Water Quality Control Commission meeting in October 2006 and will be finalized in mid 2007. As the sources of information on PQLs were examined, it was evident that matrix interference, published detection limits, PQLs attainable at commercial laboratories, and extent of deviation from the methodology prescribed in EPA-approved methods needed consideration before selecting a PQL for an analytical method. There was also a concern by stakeholders that the development of new and lower PQLs could place a major economic burden on small municipalities and industrial discharges due to an increase in analytical cost that could be realized with more expensive analyses required to achieve lower detection limits. Participating chemists identified analytical method "drift" as a concern. There have been many changes in analytical techniques due to state-of-the-art advances since many of the EPA-approved methods were established in the 1970 to 1990 period. There was also a desire for the PQLs and guidance document to be applicable to not only wastewater effluents, but also regulations of other implementing agencies.