Introducing our Four-Part Water Purity Series

Over the coming weeks, Ultimate Labs will be posting a series of blogs about water testing. We want to share what we know, to help laboratories like yours secure compliance and achieve water safety, with as little work and stress as possible. The information stream starts here…

Your water starts its journey at the source: a river, reservoir, aquifer, and the like. As beautiful as these natural reserves might be, the water here is full of salts, metal ions, and nucleic acids. It’s teeming with microbial (and maybe not so microbial) life and open to constant chemical change.

Thanks to the EPA’s Safe Drinking Water Act of 1974, this raw water undergoes heavy scrutiny during treatment. Dirt and particles? Filtered. Giardia? Zapped. Arsenic? Get that out of here. Uranium? Don’t even think about it.

Working in conjunction with standards laid out by regulatory organizations such as the American Society for Testing and Materials (ASTM), public water is decontaminated and processed until it meets acceptable purity levels. After treatment, your water can be safely called drinking water. It makes its way through an underground series of pipes and comes out of the tap in your kitchen (and flushes your toilet and washes your car).

But for scientists, using regular potable water to make a reagent or formulate a new drug would be like using rainwater to make soup. Water quality needs to be significantly improved for use in biomedical applications.

The United States Pharmacopeia (USP), an organization that sets global standards for medicines and foods, defines several grades of water that can be used for lab applications.

To achieve these grades, EPA-regulated drinking water is further processed by distillation, reverse osmosis, ion exchange, or a combination of these steps; to further whittle down calcium, sulfate, chloride, ammonia, and carbon dioxide levels. At this point, conductivity testing is performed to ensure the total number of inorganic molecules is low. Organic chemicals are also controlled. The end result is what the USP qualifies as purified water (PW), the go-to water grade for labs throughout the US.

But it doesn’t stop there. To take it even further, finer filtration on the micron level is applied to remove traces of bacterial endotoxins, taking the final product to an even higher level of purity. Water with a rigorously controlled microbial content can be classified as water for injection (WFI) – safe enough to inject directly into a human.

As you might imagine, laboratory and medical grade water needs to be tightly regulated and frequently tested. In this blog series we outline what scientists need to know about water purity. We look at different compliance levels and how to achieve those standards efficiently. We also examine what new methods are available to make successful water testing routine. Trust us — they’re a lot easier than the old-school wet-chemistry assays.


We hope you enjoy the posts. Any and all feedback is welcome, please send us a note to

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