Contaminants Everywhere

If you are processing environmental samples then you’ve probably dealt with contamination at some point.  If you haven’t, then you should be congratulated for creating the only laboratory on Earth that has ever been completely free of all sources of contamination!  There are many (in some cases, many many many) sources of contamination and the severity of your contamination issues can vary significantly depending on what types of samples you run, the cleanliness of your laboratory, the systems that are running, and the care with which samples are being collected, stored, prepared, run and disposed of.

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Question and Answer Time with EPA Method 8270

EPA Method 8270 is one of the 8000 series methods that outlines the preparation of wastewater samples.  It is one of dozens of methods for processing wastewaters for semivolatile organic compounds (SVOCs), all of which fall under Method SW-846.  Expand the graphic below to see the breadth of the method.

As you can imagine such a complicated method generates a lot of questions. It is a regular occurrence for me to get various questions about EPA methods but recently I have had quite a few about EPA Method 8270 and I wanted to share them in case someone else has the same questions.   You can find a great summary of Method 8270 in this blog that one of my colleagues recently wrote – Extraction of Polyphenols in Tea with Lemon Juice.

Q: Do I need a carbon cartridge for my 8270 extraction?

A:  The answer to this question is – it depends.  The purpose of the carbon cartridge is to collect the light end compounds that are not retained by the Atlantic® One Pass disk.  Which compounds are on this list?  There are a handful, but some of the more interesting compounds are those related to NDMA, benzyl alcohol, as well as surrogates like phenol-d5 and 2-fluorophenol.  When I analyze samples using Method 8270, I look at quite a few classes of compounds and some of them require a carbon cartridge to ensure that my recoveries are acceptable.

As a side note, NDMA is a known carcinogen and has made news headlines because the recalled blood pressure medication, Valsartan, was found to be tainted with NDMA.  The EPA also put out a technical fact sheet on NDMA in 2014 that provides some interesting facts.

Q: What is the purpose of the acetone in the elution steps using the Atlantic® One Pass disk and carbon cartridge using the method in your application note?

A:  Well, one reason to use acetone is for elution.  That’s not the main reason for using this solvent, however.  Samples that are processed using Method 8270 are typically dirty samples with high levels of particulates or suspended solids.  That means a decent amount of sediment will need to be filtered by your Fast Flow Disk Holder.  In the process of filtering out the solid material, some of your water could get trapped in the disk holder.  If we moved straight from the aqueous phase to using dichloromethane (DCM) – which is immiscible with water – the residual water would form a barrier, preventing the DCM from passing through the disk.  Acetone removes any residual water before DCM is used.

Once the DCM step is complete, acetone is used again to remove any residual DCM.  The next step in the elution process involves the use of 1% ammonium hydroxide (NH4OH) in water so all remaining DCM must be gone before proceeding to this step.  Believe it or not, acetone is used once again after the dilute ammonium hydroxide solution has passed through the disk because DCM is used to elute analytes from the carbon cartridge.  When you think about it, acetone is pretty integral to the elution process!

Fun fact:  The carbon cartridge is loaded from the bottom up in the sample processing stage so you don’t have to use as much solvent to elute your target analytes.

What are your burning, or more likely evaporating, questions about 8270?

Reducing the Headache of Challenging Emulsions

Have you ever opened a jar of olives and noticed the shimmering liquid floating on the surface?  Believe it or not, that liquid is actually residual oil that is given off by the olives themselves.  Since the oil is less dense than the aqueous solution that the olives are stored in (olive brine), it floats to the top of the jar.  This may not seem like a big concern to the typical olive consumer, however, olive manufacturers believe that too much oil in a jar is something that negatively affects the final product.  For this reason, olive companies are putting effort and resource into finding a way to quantify the amount of oil in their final product.

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What’s Your Grade?

“I’m usually ACS, although sometimes I’m Reagent.”

If you’re reading this and raising your eyebrows, you’ve never had, what I like to call, the “grade discussion.”  I don’t mean the discussion between high school or college students who are comparing grades after a big mid-term or final exam (although I used to do that too).  I mean the discussion over the solvent grade you use in your laboratory.

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Simplified BPA Analysis

Bisphenol A (BPA) is one of the most widely produced chemicals in the world – approximately 4 million metric tons annually.  In recent years, BPA has received a lot of negative attention.  In fact, I can’t remember the last time I saw a plastic item in the store that didn’t have a “BPA free” marking on it.  These labels are for good reason, though, as BPA has been found to produce negative hormonal effects within the body.  BPA is a chemical that mimics estrogen and disrupts the endocrine system, which can lead to developmental disorders, thyroid issues, diabetes and even reproductive organ cancers.  BPA is so prevalent because it has many uses in polymer chemistry.  First and foremost, BPA is used as a monomer in the production of polycarbonate, a very hard thermoplastic which has countless applications, including: water bottles, baby bottles, CDs, DVDs, eyeglass lenses and many more.

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Understanding SPE Retention Mechanisms

As a chemist, I’ve constantly stressed the importance of proper sample preparation.  Whether I’m diluting, digesting, preconcentrating, extracting, or performing a combination of these, sample preparation is the key to making my analysis a success, yet it’s often the most challenging part of my workflow.  Some of my preparation procedures are simply daunting – a series of challenging, time-consuming steps with multiple opportunities for error or cross-contamination.  On top of that is the multitude of parameters that must be selected.  Questions such as “what should the pH be?”, “which solvents should I use?” and “what should my sample volume be?” are a few of the many, many parameters that must be optimized.  When you look at all the opportunities for something to go wrong, sample preparation can seem very overwhelming.  While powerful, sample preparation becomes a lot less complicated when you understand the science behind what you’re trying to accomplish with this step.

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What does a thermistor do anyway?

It is easier to understand something when you know what the actual word means.  Thermistor is a portmanteau (yes, sometimes I do pay attention to linguistics) of the words thermal and resistor.  This means that when a thermistor is heated, its resistance is either increased or decreased based on the properties of that particular thermistor.  This property makes it very useful for many different applications all over the world.  But thermistors are most useful, at least from my perspective, when they’re used in automated solid phase extraction systems.

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Extraction of Polyphenols in Tea with Lemon Juice

For thousands of years, tea has been one of the most popular drinks around the world. Not only is tea delicious, it is also full of health benefits. Tea is an abundant source of antioxidants called polyphenols. One of these polyphenolic compounds, catechins, are found mostly in green tea. Catechins have been studied thoroughly and have been found to reduce free radical stress, they have also been found to be anti-inflammatory as well as potentially therapeutic for cancer cells.

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The Chemistry of SPE

New year – fresh start

If you’re like me, you start the new year off with a list of resolutions for the coming months – resolutions to be more fit or to secure a promotion at work or to reduce your carbon footprint. Whether you’re trying to improve your health or further your career, these are the types of goals that I like to refer to as getting “back to basics” because they require you to start with a solid foundation which you can build on to achieve success.

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Tuesday Trivia – December 11, 2018

Happy Tuesday! The final question for 2018 focuses on the EPA 500 Series methods that have been developed to quantify organic contaminants in drinking water. For those unfamiliar, EPA Method 525.2 outlines the extraction and quantification of organic compounds in drinking water. The EPA eventually revised the method and released Method 525.3. The updated revision incorporates a number of changes to improve the extraction and quantification of drinking water contaminants. Continue reading Tuesday Trivia – December 11, 2018