“Water in my extracts again?!?!”
How many of you have been in that position? You’ve worked hard to extract your samples, you’ve dried your extracts to remove the last droplets of water from your organic solvent – only to add that water back in during your evaporation step! There are fewer frustrating situations than losing a set of extracts in this manner.
If you’re like me, you work hard, follow all the precautionary step-by-step procedures to carefully produce extracts in a timely fashion. It’s frustrating to think that a whole day’s work can be ruined with just a few milliliters of water. When you see the water, you make an attempt to remove it and save your extracts, but there’s no guarantee that it’ll work. Is there any way to avoid this?
“I love doing maintenance. It’s the best part of my week” – said nobody ever.
Let’s be honest. We all dread performing maintenance. Why?
- It’s boring. I’m a chemist and I’d rather spend my time using my instrument than maintaining it.
- It seems unnecessary. I’m a fan of what I call “sensory maintenance” – that water looks pretty clean, that pump sounds pretty good.
- I don’t always know what I should be doing for preventative maintenance.
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.”
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.
Have you ever wondered why solution flow rates are so important when performing sample preparation with solid phase extraction (SPE)? If you have, read on – I have the answer for you!
Throughout my college career, the phrase “like dissolves like” was referred to quite frequently. This phrase was particularly relevant when we did solubility experiments and for good reason – it’s 100% true! Solvents tend to dissolve solutes with physical and chemical properties that are similar to theirs. Other factors such as temperature, pressure and pH can affect the solubility of solutes as well, but let’s just keep it simple for the purposes of this discussion and keep it focused on physical and chemical properties. Given this simplistic definition of solubility, the opposite stands true as well – solutes don’t tend to dissolve into solvents with differing physical and chemical properties. These solvents and solutes want to stay as far from each other as is possible.