If you read one of my earlier posts on pesticide contamination in drinking water, you may have started to make a mental list of all the compounds you’ve heard or talked about in reference to their use in pesticides. If so, two of those compounds were likely paraquat and diquat.
These compounds are complex dipyridyls but with chemical names like 1,1′-dimethyl-4,4′- bipyridilium dichloride salt and 1,1′-ethylene-2,2′-bipyridilium dibromide salt, I assume you’re like me and refer to them as paraquat and diquat, respectively. Dipyridyls are effective herbicides which is why they are so commonly used to eradicate unruly weeds. Unfortunately, many herbicide products are non-selective and will kill a variety of plants, flowers and grasses along with those pesky weeds.
With the prevalence of contaminants in wastewater today, it is important to have a method for properly extracting and quantifying those compounds, to allow our wastewater treatment plants to remove them during the treatment process, when and where they need to.
The U.S. EPA has written a number of methods for determining contaminants in wastewater – compounds from organophosphorus pesticides (Method 614.1) to organochlorine pesticides (Method 608.3) to chlorinated hydrocarbons (Method 612) have EPA-published methods for guidance. The method I want to focus on here is that for determining bases, neutrals and acids (Method 625.1) and I’m highlighting it because there’s been a change in how this method can be executed, which could have a significant impact on your laboratory. Curious about what I’m alluding to? Read on!
If you were ever a fan of the show MythBusters, you can appreciate the hours I spent watching myths being confirmed or busted in the most entertaining ways. For me, this show was appealing because the scientific theory was used to design and test experiments to produce facts about interesting phenomena such as: humans use only 10% of their brains, a household vacuum cleaner can generate enough suction to lift a car into the air, or a goldfish’s memory is only 3 seconds long.
1,4 dioxane – sometimes referred to as just dioxane – has gotten a lot of press since the U.S. EPA added it to the third Unregulated Contaminant Monitoring Rule (UCMR 3). It is a relatively common solvent in analytical laboratories; however, it also finds use as a stabilizer for manufacturing items such as shampoo, cosmetics and food additives. After the EPA deemed this compound “likely to be carcinogenic to humans” and found it in a number of groundwater sources across the U.S., 1,4 dioxane was added to the UCMR 3 list and is now a regulated, routinely monitored contaminant.
If you’ve ever taken on a home renovation project and needed to purchase wall paint, you may have looked at “low VOC” or “no VOC” paint. Even if you don’t know what VOCs are, you are likely familiar with the terrible, headache-inducing smell that greets you when you pry the lid off a new can. Not only is the odor unpleasant, but the fumes are harmful when you breathe them in over a prolonged period of time.
Solvent drying is a key step in many laboratories that are using organic solvents for syntheses and extractions. In the case of hexane extractions during oil and grease measurements, this step is necessary to ensure that the extracts are accurately dried, concentrated and weighed.