If you are tired of shaking liquid-liquid extractions (LLE) and want to move onto a technique that is less labor-intensive, solid phase extraction (SPE) may be your answer! There are manual as well as automated options available for solid phase extraction. It may seem like more work for your lab to move to a different technique, but what you gain in time savings may be worth it to you in the end.
Continue reading Why move to Manual or Automated Solid Phase Extraction?
When in the lab I always try to streamline and improve workflows. One of the biggest bottlenecks in the lab I’ve experienced and maybe you have too, is the drying of sample extracts. When extracting environmental samples, they likely have residual water. Removing water from environmental samples ensures you will get the most accurate and consistent results with both analytical and gravimetric methods. The drying of extracts can be either defined by the method or may have flexibility allowing you to use what is available as long as all quality control criteria are satisfied.
Continue reading A New Time Saving Inline Drying Solution for Method 1664B
Every step within a solid phase extraction (SPE) procedure is imperative, but one of the most important steps that must be done properly is the air-dry step. As you may know, the conditioning step prepares the SPE prior to the sample load to ensure that the sample load process will capture the analytes of interest within the media bed. However, once the sample is done loading, there is a lot of water that is left on the disk. Depending on the solvents that you are using following sample load and the analytes you are capturing, an improperly dried SPE disk could ruin your day.
Continue reading Why does your SPE disk need to be dry?
Per- and polyfluoroalkyl substances (PFAS) are a group of harmful organic compounds that are very persistent in structure. What this means is PFAS compounds accumulate in the environment over time as they do not break down easily. This makes it a concern to regulate and test these compounds as they have been shown to have adverse effects. One of the most common ways that someone would come in contact with PFAS is through drinking water. There are two notable EPA regulated methods that laboratories can use to analyze PFAS compounds, EPA method 533 and 537.1. When evaluating how to handle these methods in your lab there are some key differences in how to approach PFAS testing. See our earlier blog extracting perfluorinated compounds from drinking water – why is it so challenging?
EPA method 533 is a compliment to method 537.1, including an additional 11 compounds and excluding 4 compounds from 537.1. When used together, twenty-nine compounds can be tested in drinking water. All of these can be visualized in the table below, showing the acronyms for each compound and what methods they are tested in. Specifically, method 533 focuses on PFAS compounds that have short carbon chains, which are those with carbon lengths of C4 to C12. The first major difference between the two methods is the type of solid-phase extraction media that is used. Method 533 uses polystyrene divinylbenzene with a positively charge diamnino ligand and isotope dilution whereas method 537.1 uses styrene-divinylbenzene (SDVB) media. So, when it comes to preparing for the extraction of these compounds it is important to ensure that you are using the right type of cartridge to get the best results. The other major difference that goes hand-in-hand with the media type, is how the extraction techniques differ. With method 533; methanol and 2% ammonium hydroxide are used for extraction elutions, evaporated to dryness with a nitrogen blowdown and water bath, and then reconstituted with 20% water in methanol. However, with method 537.1, just methanol is used for extraction elutions and after it has been concentrated to dryness it is reconstituted with a 96:4 methanol:water mixture instead.
In summary, while the overall extraction process is similar, the media type, elution solvents, and reconstitution process differ between the two methods. These are the key things that you need to keep in line so that the similar extractions do not get mixed up. The easiest part to keep together is the fact that despite the differences in the extraction methods, both are analyzed on LC-MS-MS. Hopefully, this helps you to get started on understanding the key differences between the two methods and how to extract them.
If you are looking to certify or currently running EPA method 533 and or 537.1 in your lab I have included links to Biotage solutions that can help to get you started and improve your laboratory’s workflow.
TurboVap® LV Automated Solvent Evaporation System
ISOLUTE® 101 SPE column
EVOLUTE® EXPRESS Wax in a 6-mL format (150 mg) or
EVOLUTE® EXPRESS WAX 500 mg bed mass
Ugh…I think we can all agree that the worst thing that can happen when testing high profile samples is losing an extract due to phthalate contamination. Whether you are extracting 525.2 or 625.1 samples, phthalates can ruin your day and wreak great havoc, causing false positives! We wonder where they all come from and how they got in the extract in the first place because we try our best to make sure our lab supplies and instruments are clean. As we all know though…phthalates are literally everywhere floating around in the air and settling on surfaces. However, I am here to talk about one place in particular: solvent squeeze bottles. We take extra precautions when refilling our squeeze bottles, but there is always the potential of introducing phthalates into them if they are not refilled or used properly.
Continue reading Common Mistakes by the Lab Series: The Pain of Contaminated Squeeze Bottles
When juggling the responsibilities of working in a sample preparation lab as well as working as an analyst, it is very easy to get caught up in a never-ending cycle of samples. There is no situation “more frustrating” then when you have a bunch of wastewater samples that need to be extracted and analyzed ASAP and there is that one sample that is so much more challenging to extract than the others. After struggling all-day-long, you finally get the batch of rush samples set up to run on your gas chromatography (GC) system overnight only to come in the next morning to find that your mid and closing check standards are low and the data is effectively useless!
Continue reading How to plan for dirty samples for both extraction and analysis
EPA Method 1664B
Have you ever had days of extracting oil and grease samples and thought to yourself “there must be an easier way to work with wastewater samples”? Whether you run oil and grease samples by liquid-liquid extraction (LLE) or by solid-phase extraction (SPE) it can be challenging at times to efficiently extract 1-liter samples due to the sample matrix. Wastewater is challenging and can be very complicated and contain many types of particulates and or detergents. The makeup of the sample not only interferes with efficient extractions due to matrix issues (such as emulsions) but can also cause slow flow rates.
Continue reading Myth Busters: Smaller Sample Volumes
Have you ever thought to yourself I wish there was one way to effectively extract all of our aqueous samples? For instance, there are several methods available to extract aqueous samples, such as extraction method 3510 liquid-liquid extraction (LLE), method 3520 continuous liquid-liquid extraction (CLLE), and method 3535 solid-phase extraction (SPE). Wouldn’t it be more convenient to use one extraction method within the lab for most if not all of your aqueous extractions?
Continue reading Simplifying Water Extractions with SPE – One Matrix, One Method Extraction
Working in an environmental lab requires a lot of concentration, both mentally and for the samples that you are working with. When New England finally begins to thaw and local companies rush to get their samples completed, a bottleneck that is usually experienced is the drying and concentration of so many samples. This bottleneck is partly due to ensuring that samples are extracted within their holding times. There have been many times I have had to multitask while concentrating samples on the TurboVap® classic, leading to some extra work when that rare sample was overconcentrated. Many of my past coworkers brought up the challenge they faced with the extraction of water and soils. In my opinion, the bigger issue was drying and concentrating. My main complaint with these steps was it was never efficient enough and I always had to baby each step so that all of my hard work (shaking the sample) did not go to waste. What I strived for most in the lab was an efficient and streamlined workflow for this part of the process.
Continue reading Overcoming drying and concentrating bottlenecks in the lab