Paraquat and Diquat Use in Pesticides

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.

For those (like me) who like to combat everything from crab grass to poison ivy, to dandelion weeds in one swift chemical attack, you take your bottle of non-selective herbicides and spray your lawn until every inch of it is covered. Unfortunately, those same chemicals that make our gardens look spectacular are the same chemicals that can be washed away with the rain or can sink into the surrounding soil and contaminate our drinking water sources.

Did you know: there are no contaminate regulations, nor testing requirements for well water and other private drinking water sources?

Under the Safe Drinking Water Act (SDWA), the U.S. EPA regulates and monitors a number of contaminants in our drinking water supplies that could cause us harm. Pesticides are included in that list; however, it’s not a trivial task as the health risk varies based on a number of factors including: the toxicity of the herbicide, the extent of its use and its persistence in the environment. Therefore, the EPA works with state and local agencies after establishing federal guidelines on pesticides to ensure that water testing facilities are able to monitor pesticides at a local level.

There are a number of methods established by the EPA for quantifying pesticides in drinking water. Each method caters to the chemical and physical properties of the pesticides under investigation, which is important in accurately extracting and quantifying them. Given the similar properties exhibited by paraquat and diquat in water, EPA Method 549.2 was established to target them specifically. Check out this application note to see how an automated, cartridge-based solid-phase extraction system streamlines the extraction process outlined in Method 549.2 to streamline this application and improve your laboratory productivity.

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