API Publ 4721-2002 pdf download.Analytical Detection and Quantification Limits: Survey of State and Federal Approaches.
The American Petroleum Institute (API) conducted a review of state policies related to analytical detection and quantification limits, with particular focus on water quality and wastewater issues in permitting and compliance. Ten states were reviewed: Alabama, California, Illinois, Louisiana, New Jersey, Ohio, Oklahoma, Pennsylvania, Texas, and Washington. Summary findings of this review are: § Every state incorporates detection or quantification terms in its regulations. Terms referenced in regulations are usually defined in the regulations, but not always. The most frequently used terms are detection limit/level, method detection limit (MDL), and practical quantitation level (PQL). Minimum level (ML) is used by Alabama, California, Illinois, and Ohio.` § The states vary in the extent to which detection and quantification terms are incorporated into their regulatory language. Some states prefer to have the most detailed policies in their water quality implementation procedures; other states prefer to put the detail directly in the regulations. § The states will set wastewater permit limits at or below detection or quantification levels, where considered protective of water quality. Most states specify, either in their regulations or implementation procedures, how compliance is demonstrated in such cases. Compliance with a maximum concentration limit is demonstrated by a Òless-thanÓ analytical result (a detection or quantification limit, as applicable). Where a mass load or average concentration is calculated, most states specify that zero be used in lieu of less-than values. In some situations, one-half the detection limit must be used. § Although the states have procedures for allowing wastewater permittees to develop site-specific detection or quantification limits based on state- or EPA- defined methods, none of the states had specific procedures for developing or approving alternative methods.
Overview of Report Presented first is an overview of approaches for analytical detection and quantification limits in environmental programs. The overview describes various detection and quantification terms, including method detection limit (MDL), minimum level (ML), practical quantitation (or quantification) level (PQL), alternative minimum level (AML), interlaboratory quantification estimate (IQE), and others. Next, the policies of the ten selected states are presented. Lastly, recommendations are provided for setting effluent limits and compliance monitoring requirements in wastewater discharge permits. Overview of Approaches This section provides an overview of selected approaches for determining analytical detection and quantification levels used in environmental programs. Table 1 lists the terms most often used in these programs, as well as two alternatives (AML, IQE) that have been suggested by others. In the following sections, these terms, as they are used in wastewater programs, are discussed in detail, and their similarities and differences are compared. Terms used in other environmental programs, both state and federal, are identified. Water and Wastewater Programs The most common detection and quantification limits in water and wastewater programs are the MDL, ML, and PQL. The MDL can be used to calculate both the ML and the PQL. Variations of these and other related terms can be found in water and wastewater programs.
Alternative Minimum Level The AML is defined by Gibbons et al. (1997) on the same basis as USEPAÕs ML, but with notable differences. Like the ML, the AML is defined as the concentration at which the instrument response is 10 times the standard deviation, s. With the AML, the standard deviation is calculated as a function of concentration, whereas the ML uses a fixed standard deviation from a set of replicate analyses. The AML can account for interlaboratory variability and sample matrix effects. Where only single laboratory (intralaboratory) data are available, an adjustment is made to estimate an interlaboratory value. Other Terms Other quantification terms used in state programs are discussed in State Policies . Those found in federal regulations are listed in Table 2. Definitions are included in Table 2 if they were given in the regulations. No references to analytical quantification terms were found in federal environmental statutes. Comparison of Approaches A comparison of the USEPAÕs approaches (MDL, ML, PQL) to the alternate AML and IQE is provided in Table 3. The LOD and LOQ approaches are included in the comparison because of their relationship to the others. Table 3 lists for each term its calculation basis, its advantages, and its disadvantages or issues of concern.