Simplified Extraction of Semivolatile Organics by EPA Method 625.1

Oral Presentation

Prepared by A. Pierri
Weck Laboratories, 14859 Clark Ave., Industry, CA, 91745, United States


Contact Information: agustin.pierri@wecklabs.com; 626-336-2139


ABSTRACT

EPA method 625 was written for the determination of a large list of GC amenable organic compounds that partition into an organic solvent out of municipal and industrial wastewaters. Over the past several decades, the method has been updated to incorporate advances in technology, including the most recent Method Update Rule (MUR) which allows the use of GC-MS/MS and solid phase extraction. An inherent challenge of method 625 is that the liquid-liquid extraction process is laborious and resource-intensive—it requires two different extraction steps, and a few hundred milliliters of solvent. The recent MUR allows the use of solid phase extraction (SPE) to alleviate this tedious process, but SPE also presents certain challenges because the extraction efficiencies for all targets are not are not uniform since they encompass a variety of different chemical classes.

This paper presents a modification to the method where a supported liquid extraction (SLE) cartridge is used for the extraction portion, and a sensitive GC-MS/MS is used for the analytical portion. The original method calls for a 1 L portion of sample to be extracted and concentrated to a small volume to achieve the required reporting limits. However, by leveraging the extreme sensitivity of modern triple-quadrupole mass spectrometers, we can achieve the same reporting limits from a sample volume of only a few milliliters. To facilitate the extraction of such a small sample volume, we can use SLE to support the sample on a solid phase material, while extracting the sample with an excess of solvent. The large surface area of the sorbent allows for a very efficient extraction, resulting in very high recoveries for targets with traditionally low recoveries—such as the PAHs and nitrosamines.