“There is a child in every one of us who is still a trick-or-treater looking for a brightly-lit front porch.” – Robert Brault
Volatile. Flammable. Skin irritant. Respiratory irritant. Possibly fatal if swallowed. For those of you processing samples according to EPA Method 1664B, you’ve seen these hazard descriptions before – on the safety data sheet (SDS) for n-hexane. For those of you who aren’t familiar with (or have forgotten about) the hazards related to n-hexane, those are just a few. It also smells unpleasant and could explode if heated. It’s a relatively unpleasant organic solvent to work with and it begs the question:
Is there an alternative?
“Why do I keep seeing background contamination from phthalate and adipate when I do extractions for semi-volatiles?”
This is one of the most common questions I’ve been asked when I’m traveling in the field. It’s an issue I’ve come across in my own lab on occasion and if you can’t find the source of your contamination, it can turn routine application work into a troubleshooting nightmare. Given how often I’ve seen these compounds cause contamination issues, I thought I’d review some of the most common sources for these. Continue reading 5 Sources of Phthalate and Adipate Contamination You Probably Didn’t Know About
“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.
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.
Since its release in 1995, EPA method 525.2 has been one of the most widely used methods for quantifying semi-volatile compounds in drinking water. Chances are, if you work for or own a drinking water lab, you probably analyze for compounds in this method – at the very least, you’re probably at least familiar with the method. This is a widely accepted method for quantifying semi-volatile organic compounds; however, there are some glaring issues with the method that the EPA has recognized and addressed. These changes have been collected and implemented in a new revision – Method 525.3 – which was published in 2012. Method 525.2 is still more frequently used by laboratories processing drinking water samples; however, I would argue that Method 525.3 is more scientifically sound. In this 2-part blog series, I will address multiple aspects of Method 525.2 that have been modified to improve the collection, preservation, and processing of drinking water samples. In this first part, I will focus on the improvements that have been made with respect to the sample preservation process.
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?
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?
In a never-ending list of chemical pollutants, a compound that is gaining a lot of attention is 1,4-dioxane. In fact, New Jersey just became the first state to set regulations on the quantity of 1,4-dioxane that can be present in drinking water.
1,4-dioxane, commonly called dioxane (the other two isomers – 1,2-dioxane and 1,3-dioxane are rarely ever seen), is an ether with the molecular formula of C4H8O2. Dioxane was previously used as a polar aprotic solvent. For those who remember their organic chemistry from college, SN2 reactions involve the use of polar aprotic solvents. Since its original use in laboratories, dioxane has been determined to be carcinogenic and, unlike many organic pollutants, it is completely soluble in water. Dioxane’s use as a solvent for industrial purposes has been mostly replaced with tetrahydrofuran, which has a higher boiling point and a lower toxicity. However, the story does not end there!