Development of U.S. EPA Method 551.1

As initially written, U.S. EPA method 551 included 12 chlorination disinfection byproducts and six halogenated solvents. This method is significantly revised as U.S. EPA method 551.1 to include 12 commonly observed chlorination disinfection byproducts, eight halogenated organic solvents, and 17 pesticides and herbicides. The applicability of the revised method has increased as a consequence of the larger analyte list. In addition, built into the method is the flexibility to choose only those analytes from the list which are critical to a specific application. Several procedural modifications are incorporated into the method, such as simplifying sample preservation, specifying a different salting agent, allowing the conditional use of pentane as an alternate extraction solvent, and recommending simultaneous confirmation analysis. Data are presented that illustrate the importance of including these method modifications into U.S. EPA method 551.1.