With the prevalence of contaminants in wastewater today, it is important to have a method for properly extracting and quantifying those compounds, to allow our wastewater treatment plants to remove them during the treatment process, when and where they need to.
The U.S. EPA has written a number of methods for determining contaminants in wastewater – compounds from organophosphorus pesticides (Method 614.1) to organochlorine pesticides (Method 608.3) to chlorinated hydrocarbons (Method 612) have EPA-published methods for guidance. The method I want to focus on here is that for determining bases, neutrals and acids (Method 625.1) and I’m highlighting it because there’s been a change in how this method can be executed, which could have a significant impact on your laboratory. Curious about what I’m alluding to? Read on!
For those unfamiliar with it, Method 625 outlines the determination of over 300 organic compounds (364 compounds, to be exact) in municipal and industrial wastewaters. This list includes polynuclear aromatic hydrocarbons (PAHs), pesticides, phthalate esters, nitrosamines, haloethers, aldehydes, ethers, ketones, pyridines, quinolones, phenols and many many more. As you might imagine, 364 compounds will differ slightly in their chemical properties so extracting all of them for accurate quantification by GC-MS requires a multi-step extraction process with a number of challenges and opportunities for error or contamination.
In its original form, this method outlines an extraction procedure that uses either liquid-liquid extraction (LLE) or continuous liquid-liquid extraction (CLLE), followed by sodium sulfate drying. This approach has been mastered by many laboratories; however, it is a very labor-intensive, time-consuming process that requires a lot of solvent (which generates a lot of hazardous waste) and often produces emulsions.
The EPA has taken this information into account and, using the Method Update Rule (MUR), updated Method 625 to allow solid phase extraction to be used for the extraction of organic compounds in wastewater samples, with a supporting validation study – hence, why the method was updated to version 1.1. This change went live in September 2017 so laboratories may now use SPE to process their wastewater samples, in compliance with Method 625 regulations! Solid phase extraction is a well-established technique for extracting volatile and semi-volatile organic compounds and provides significant benefits, including: improved accuracy and reproducibility, reduced solvent usage and hazardous waste generation, elimination of emulsions and reduction in opportunities for contamination. Not familiar with SPE? Check out this blog post and video for a quick overview.
As long as your quality control acceptance criteria are met, you can use SPE for all your sample preparation work. Furthermore, if you use SPE equipment that has been fully validated under Method 625.1, that QC and performance data can be used to validate your laboratory to use SPE for preparing all your samples for analysis under Method 625.1 guidelines.
So what does that mean for you? It means that you could be using SPE to process your samples – reducing solvent usage, sample preparation errors and contamination, QC failures, and time spent processing each and every one of your samples. Want to learn more? Here’s an application note and a Method 625.1 validation package that shows you what I’m talking about.