If you’re familiar with methylene chloride (which I’m sure you are since it’s one of the most widely used laboratory solvents), you know that it’s developed a reputation for being one of the “bad boys” of the solvent world. The bad press has certainly been earned. It’s been attributed to over 60 deaths in the last 4 decades. It’s also pretty aggressive – exposure to just a few ounces for a few minutes can be enough to cause severe damage or death. And since it’s a colorless liquid, an innocent-looking spill could be a severely harmful hazard.
“Our laboratory uses organic solvents every day. Should we be concerned about solvent exposure?”
I hear this question fairly often and the short and simple answer is: YES.
But if this were a simple yes/no question, I wouldn’t have anything else to say, and this would be the shortest blog post that’s ever been written.
On the surface, EPA Method 8270 seems pretty straightforward. The first version of this method was published over a decade ago and many environmental labs are processing samples according to the guidelines in this method. The EPA summarizes the goals of the method in a single sentence on their website:
“This method [is] for analysis of solid, non-drinking water, drinking water and/or wipe samples containing select semi-volatile organic compounds.”
“Pesticides” is one of those terms that invokes a wide range of emotions in people. Some people smile when they think of the insecticides that keep their award-winning flower garden looking beautiful all season. Some people feel grateful for the algaecides in their fish tank that let their kids’ pet fish (who’ve probably been given cute names like “Nemo” and “Frankie Fish”) swim around freely, without having to navigate around huge algae blooms. Then there are other people who hear the word “pesticides” and think of dangerous chemicals that are sprayed onto our crops, eventually ending up in our food and water supply. In this post, I’m going to walk through the good, the bad and the ugly when it comes to pesticides, but that term actually includes a huge number of compounds, so I’m going to narrow my focus to just organochlorine pesticides for the purposes of this post.
The U.S. EPA monitors a variety of compounds that pose public health risks when they are present in our air, soil or water and they have spent decades publishing methods to help us extract and quantify those compounds. The 8000 Series EPA Methods describe the extraction and analysis of contaminants in groundwater and Method 8270 specifically covers semi-volatile compounds. The EPA has been monitoring semi-volatile compounds in solid waste, soils and groundwater for almost 40 years, and Method 8270 has undergone several revisions during that time. For example, revision C allowed air samples to be included in the list of sample matrices that can be analyzed under this method.
Solid phase extraction (SPE) is a powerful sample preparation tool that makes it possible to extract semi-volatile organic compounds with varying physical and chemical properties. When used properly, this tool will simultaneously extract hundreds of analytes from the most challenging sample matrices. When used improperly – well, this tool can quickly become as effective as using a hammer to paint the walls in your house.
In the first part of this 2-part blog series, I highlighted the improvements made by the EPA regarding the preparation and preservation of samples. In this post, I will focus more on the changes the EPA has made to Method 525 which affect the analysis of the prepared samples.
Solid phase extraction is a powerful technique – it can be used to clean up the most challenging samples, and extract and preconcentrate hundreds of semivolatile organic compounds. When performing the extraction, the goal is to get the entire sample to run through the extraction disk. But in order to do that, the disk must have the chemical and physical capacity to handle your sample matrix. If your disk becomes overwhelmed or clogs, you risk losing your sample and the chance to complete your extraction.
How do you prevent the disk from clogging? Prefilters!