The Hidden Dangers of Organic Solvents

“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.

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Everything You Wanted to Know About EPA Method 8270 But Were Afraid to Ask

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.”

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Organochlorine Pesticides: The Good, the Bad and the Ugly

“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.

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6 Changes to EPA Method 8270 That You May Not Be Aware Of

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.

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7 Horrible Mistakes You’re Making with Solid Phase Extraction

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.

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Improvements in Processing Drinking Water Samples by Method 525, Part 2: Extraction Procedure

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.

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Why are Phenols so Challenging to Extract from Water?

Phenolic compounds can be some of the most challenging compounds to extract from the compound lists in EPA Method 8270 and EPA Method 625.1.  The recovery of these compounds suffer tremendously compared to some of the other target analytes on the list.  So what exactly are phenols and why are they challenging to extract and quantitate?

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Solid Phase Extraction of Drinking Water – How do I Dry My Extracts?

If you’re a laboratory that’s processing drinking water samples using solid phase extraction, you’ve inevitably gotten to the step in your procedure where you’ve eluted your analytes from your SPE media and you find yourself saying “How do I dry my extracts?”

What’s the best way to dry my extracts? 

This is a question we get quite frequently and it’s a reasonable question to ask.  Unfortunately, the answer is – it depends.  Solvent drying (not to be confused with solvent evaporation) is an important step in your extraction process when you’re using organic solvents to elute your target analytes.  Residual water in your solvent can cause issues if your target analytes extract back out of the solvent and into the water while you’re trying to evaporate or analyze your sample.  Water can also damage your chromatography system, so if you’re quantifying your extracts by GC/MS or LC/MS, you want your solvent extracts to be dry prior to analysis.

So, given the importance in solvent drying, I thought I’d share some of the commonly asked questions that come up under this topic.

Q: I’m processing my samples against EPA Method 525.3.  Does it matter how I dry my extracts?

A: If your lab is being audited against EPA Method 525.3, you need to dry your extracts per the recommended procedure – in this case, sodium sulfate.  Make sure you purchase the recommended grade of anhydrous sulfate and store it appropriately.

If your lab processes a large volume of samples, you may have sought out alternative approaches to solvent drying, such as phase separation membrane.  While sodium sulfate is readily available for purchase in bulk quantities and is pretty easy to learn how to use, it has some potential downsides to it.

  • It has to be dried and carefully stored, which is time-consuming and requires you to have adequate drying and storage equipment
  • It has to be disposed of as hazardous waste
  • It’s a chemical that dries your solvent by reacting with water to form a hydrated salt, which means it can retain some of your target compounds (particularly those that are highly water soluble)
  • It can contaminate your extract, particularly if it’s stored incorrectly or purchased at a lower grade than is recommended
  • It can be saturated. What that means is, if you didn’t calculate the mass of sodium sulfate you needed, given the volume of water you needed to remove, you could exceed the capacity of the salt and end up with a solvent that’s not completely dry

Phase separation membranes physically separate the water from your solvent, which eliminates all of the challenges you face with a chemical drying agent such as sodium sulfate.  Plus, it’s compact and easy to store, intuitive to use and easy to dispose of.

There are a handful of benefits to using a phase separation membrane over sodium sulfate – just make sure you check the method you’re following and adhere to the drying method outlined there (if there is one).  Check out the method summary in this app note for an example protocol that adheres to EPA Method 525.3 guidelines.

Q: Since EPA Method 525.3 specifies that I use sodium sulfate, can I put sodium sulfate on top of phase separation membrane to dry my extracts?

A: While clever, this is an idea that you would want to run past your auditor first.  Since the method specifies the use of sodium sulfate but does not specify the physical separation of water (using a phase separation membrane, for example), physical separation isn’t forbidden, but it’s also not specifically allowed.  Yep, this one is a gray area so have a conversation with your auditor before cleverly devising a drying setup that includes both chemical and physical solvent drying.

Q: I’m running samples against EPA Method 525.2.  Do the same rules apply to me?

A:  Yes.  As with Method 525.3, this method specifies the use of sodium sulfate.

Q: I’m not processing samples against an EPA Regulated Method and my protocol doesn’t specify a protocol for extract drying.  What should I do?

A: If your lab is not reporting results against a method that specifies an extract drying method, you should have the option to decide whether you want to dry your extracts using physical or chemical separation (double check your laboratory’s established protocols to make sure your SOP allows you this flexibility).

If this decision were up to me, I’d order myself a huge stack of DryDisk® Disks and wave goodbye to sodium sulfate forever!

Do you prefer physical drying over chemical drying?  If so, let us know in the comments and share this post to spread the word!

Which Media Type is Right for my Environmental Application?

In the world of solid phase extraction (SPE), the list of media that is available seems to be ever-growing.  From polymeric stationary phases, to silica-based media, and even molecularly imprinted polymers specifically designed for target analytes.  The possibilities seem endless.  Luckily for us, most EPA methods specify which media type is required for analysis, but what about methods that don’t specify?

For the methods which don’t specify the media you must use, how do you select your media type?

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Better Water Testing for Safer Produce

“Do what you can, with what you have, where you are.”
-Theodore Roosevelt

As the seasons change, I’m reminded of this quote and its significance to the air, land and water that sustain us.  As the weather gets warmer and winter transitions into spring, I love listening to the sound of birds chirping in the morning and watching new flowers blossom.  I look forward to the coming weeks and months of picking strawberries, raspberries, cucumbers and a myriad of other fresh fruits and vegetables.  There’s nothing like the feel of the warm sun and a gentle breeze as you pluck a fresh apple from a tree and bite into it.

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