Keeping Your Water Pure and Your Results Reliable

By Kylie Wolfe

What’s the one thing you can’t live without? Water and its simple chemical formula aids our body’s complex systems. It keeps our cells alive and internal temperature in check. It’s a large part of what makes Earth inhabitable — because without it, we couldn’t survive more than a few days.

“We drink it, we bathe in it, we use it to clean,” said Kim Knepper, water service product specialist at Thermo Fisher Scientific. “It’s a staple in our lives and very universal for laboratory work as well.”

Water is an essential part of the lab, but it can be a source of contamination, too. Catching contamination early and maintaining your water’s purity can help you achieve the most accurate results. Whether your water is used for general purposes, analytical testing, or life sciences applications, it’s important to remove impurities before they become problems.

Setting Standards

While there are many sources of error in a lab experiment, there’s one you can control from the start. Don’t let water negatively affect your work — use the following information to help you set standards for water purification and use.

Run water through your system first. When you dispense water from your purification system, make sure it’s displaying the proper purity for your application. You should also discard the first water dispensed from the system and avoid adding additional tubing to the filter. Ideally, the water you use should come directly from the system.

Knepper recommends discarding the first liter of water, especially if it hasn’t been in use for eight or more hours, to “flush the point-of-use filter [and get rid of] any potential impurities that have collected from the atmosphere.” Throughout the day, you only need to dispose of the first 50 to 100 milliliters.

Always empty water that’s been sitting. If you refill a container with purified water, always empty it before adding new water. Do not top it off. Contaminants can accumulate in water that’s been exposed to the air.

“Think about your drinking water bottle,” said Knepper. “When you’re constantly drinking out of it, and you leave some water behind, then you refill it again, you have a little bit of stale water still in there. Eventually the water does not taste as fresh. As a best practice, people should dump out their old water before they refill with fresh drinking water — same thing with the water in a container in the lab.”

Use the right kind of bottle. There are different bottle materials, and they serve different purposes. Depending on your application, make an informed decision between plastic and glass before beginning a new experiment.

“Pure water is not its natural state, and it will absorb anything it can back into it — including CO2 from the air, vapors, and anything that can be leached from the bottle,” said Knepper. “Therefore, if the application is sensitive to organics, use a glass bottle for storage. If the application is sensitive to ions, use a plastic bottle made of inert materials.”

Maintain your water system. Replace filters and cartridges regularly to make sure you’re dispensing water at the level of quality you expect. This will help ensure that water is not a source of error in your experiments.

“It’s no different than changing an oil filter in your car and checking your belts. You want to do the same thing with your water system to ensure it’s able to give you purified water when you need it,” said Knepper.

Acknowledging Impurities

Impurities can range from undesired chemicals to microbial contaminants. Some of the most common include suspended particles, colloids, and inorganic ions. The presence of these contaminants can interfere with instrument operation, clog filters, disrupt ion exchange, and affect cartridge life.

These impurities also come from a variety of places. In the lab, cleaning supplies, gloves, furniture, and even skin can contribute. That’s why it’s especially important to evaluate the quality of your water before you begin an experiment. This requires the right water purification system and proper maintenance — critical steps for your scientific research.

Selecting a Water Purification System

When selecting a water purification system or method, it’s helpful to understand your water source, its contents, and how its impurities can impact your experiments. Consider the amount of water you use and how you’ll be using it. The acronym FAVOR can help you make this assessment.

F – Feed: What is your water source? There are varying levels of water quality, so you should understand what you’re feeding your system, including the types of impurities you need to address.

A – Application: What will you be doing with the water? List your most critical applications and determine which impurities they’ll be most sensitive to. The system you choose should be able to address those concerns.

V – Volume: How much water do you use each day or week? Knowing this answer will help you determine the size of the system needed to keep up with your demand. It’ll also save you from waiting to purify additional water.

O – Orientation: Where do you plan to set up your system? There are different kinds of units, some that can hang on the wall and others that can sit on your benchtop. Knowing where you’d like to place your unit is a great next step.

R – Replacement: What works well for your lab and what doesn’t? If you’ve used water systems in the past, you might have an idea of what you liked or did not like. This will help you zero in on your new system.

Understanding Types of Water

There are so many ways to use water in the lab. Maybe you use it to dilute samples, provide a baseline for analyses, rinse glassware, or fill water baths and incubators. Because of this, there are varying levels of purity to keep in mind.

According to the American Society for Testing and Materials (ASTM), there are three main classifications of water: Type I, Type II, and Type III. They are distinct because of varying levels of resistivity, total organic carbon, sodium, chloride, and silica. Based on these values, each water type is suited for a particular application.

Type I water systems remove a large range of impurities, resulting in the highest purity water. It’s best to use Type I water, also known as ultrapure, for critical analytical and molecular applications like cell culture, chromatography, and mass spectrometry.

Type II water is often used in clinical analyzers, instrument feeds, electrochemistry applications, and sample dilution. It can be added to buffers, media, and reagents and used as a source for Type I systems. Although it isn’t considered ultrapure, it’s still pure enough for routine applications.

Type III water is less pure but the most common. It can be used to feed Type I and Type II water sources or prepare for other lab tasks. Type III water serves a much more general purpose and should be reserved for non-critical applications like glassware washers and autoclaves.

Taking Action

Prioritizing water quality can help you take your results to a new level of accuracy. Make sure to set and follow standards for water purification and use in your lab. This can include rinsing your point-of-use filters and containers and scheduling preventative maintenance. Keep track of the types of impurities you see in your water source and understand which ones need to be filtered out for your applications.

Knowing this information will help you choose the water system that’s right for your research. Even though water can be a source of contamination, it’s also an essential component of your work. Have confidence in its purity with the right systems and standards, keeping water at the center of your science every day.

This content was inspired, in part, by “Contamination in a Microbiological Laboratory,” International Journal of Research Studies in Biosciences, 2018; “Detecting and Managing Water Contaminants in the Laboratory,” Labcompare, October 2014; “There is Something in the Water,” Life in the Lab, August 2018; and “Review of The Impact of Water Quality on Reliable Laboratory Testing and Correlation with Purification Techniques,” Laboratory Medicine, November 2014

Kylie Wolfe is a Thermo Fisher Scientific staff writer.


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