TM94-12 Description and guide for interpreting low-level data supplied by the NWQL for schedules 2001, 2010, 2050, and 2051

This memorandum describes National Water Quality Laboratory (NWQL) policy for reporting and interpreting low-level analytical data for recently developed organic pesticide residue schedules2001, 2010, 2050, and 2051. Until now, there has been no standard procedure for establishing reporting levels and analytical detection limits at NWQL. For new methods, the National WaterQuality Assessment Program (NAWQA) requested statistical techniques be used to (1) estimate method detection limit (MDL), (2) eliminate censoring data below the MDL, and (3) characterize 
analytical uncertainty at low levels. Analyte detection is described using the concept of analyte identification and quantification in the context of these analytical methods. Additionally, measurement uncertainty and quantification are discussed. Method detection limits are described, based on procedures outlined by the U.S. Environmental Protection-Agency (1992), which have been adopted by most local, State, and Federal agencies working with NAWQA.