EPA Method 624.1 - A Summary of the Changes in the Newly Promulgated GC/MS Method for Volatile Organics in Wastewater

Method Update Rule
Oral Presentation

Prepared by H. McCarty, K. Roberts
CSRA, 6361 Walker Lane, Suite 300, Alexandria, VA, 22310, United States

Contact Information: harry.mccarty@csra.com; 703-461-2392


The USEPA Office of Water published a “Methods Update Rule” in 2017 that includes Method 624.1, the first substantive revision of this purge-and-trap GC/MS method for volatiles in wastewater samples since its 1984 promulgation. The revised method was developed by the Office of Water in collaboration with a wide range of other EPA organizations, commercial laboratories, and laboratory trade groups and was subjected to multiple reviews and the public comment process. The promulgated version includes all of the target analytes from the original version, many of which are subject to regulation in wastewater effluents under the NPDES program, as well as a separate list of additional analytes that were requested by the collaborators, in an effort to harmonize the method with similar volatiles methods from other EPA programs, and that may be analyzed using Method 624.1 when needed. Although the basic technology (purge-and-trap GC/MS) remains the same, the revised method is strictly a capillary column GC procedure, and is performance based, such that laboratories have the flexibility to employ new technological advances without the need to wait for formal EPA approval. The quality control procedures remain largely the same, with minor changes such as the use of a matrix spike and matrix spike duplicate pair to assess bias and precision, as opposed to the earlier discussion of one matrix spike. Some of the historical prescriptive language has been removed and where true requirements remain, the formerly implicit rationale has been explained. The Office of Water retained the method detection limits (MDLs) and quality control acceptance criteria from the 1984 version, pending completion of a new performance evaluation study of the revised method. However, given the overall improvements in instrumentation, EPA anticipates that laboratories will be able to achieve better sensitivity and better performance than in the past.