Product Manager, Nalgene Labware and Lab Containers
Working in a lab presents a number of health and safety challenges, especially when working with chemicals and solutions. On one hand, to cope with aggressive chemicals, many researchers use glass labware because of its resistance to most chemicals and solutions. On the other hand, the fragile nature of glass introduces a safety hazard that researchers must take into account. Plastic labware provides a safe alternative to glass and, when chosen and used properly, it can provide years of reliable performance.
It’s important to realize that plastic labware comes not only in many shapes and sizes, but also in various resins. Each plastic resin has its own chemical and physical properties, and these affect what you can and cannot do with the labware—what chemicals you can use, whether you can autoclave it, and if it will retain its protective elastic properties during freezer storage. When selecting plastic labware, you first need to identify a material that is compatible with the chemicals or solutions it will come into contact with in your lab. The second threshold is to check the plastic’s physical properties. In particular, you need to be sure it can handle the temperatures you have in mind.
After you have selected the best labware for your needs, you will need to care for it appropriately and inspect it regularly to achieve the best possible performance. Follow these guidelines to choose the right plastic labware for your applications.
Chemical compatibility
First, you need to think about what kinds of chemicals your plastic labware will come in contact with. Chemicals can affect the strength, flexibility, surface appearance, color, dimensions and weight of plastics. Chemical compatibility depends on what resin the labware is made from and how well the resin resists reacting with the chemical.
For example, polyethylene terephthalate copolyester (PETG) has good resistance to aliphatic alcohols, aldehydes, aliphatic hydrocarbons and dilute acids. But PETG labware is not recommended for use with bases, aromatic or halogenated hydrocarbons, aromatic ketones or concentrated acids; such chemicals can cause immediate damage to the labware.
In contrast, labware made from a fluoropolymer resin like perfluoroalkoxy (PFA) demonstrates excellent resistance to all common laboratory chemicals including halogenated hydrocarbons,aromatic ketones, acids of all strengths, bases, aliphatic alcohols, aldehydes and even strong oxidizing agents.
Temperature, duration of chemical contact and applied stresses like vacuum, pressure or g-forces of centrifugation also play a critical role in chemical resistance ratings for plastics. For example one can successfully put ethanol in a polycarbonate bottle for long term storage. However, if you put ethanol in a polycarbonate centrifuge tube and spin it at 5,000xg, the tube will crack during the first spin. It’s important to check the appropriate chemical compatibility rating charts to determine which materials will be compatible under your specific application conditions. Tool-providers have created different charts for general lab use, centrifugation, filtration and tubing applications.
Temperature resistance
The second area to investigate is the plastic’s physical properties—you need to be sure the labware can handle intended temperatures. Some plastic labware can stand up to hot-water baths and autoclaving, but not all plastics are compatible with temperature extremes. For example, polypropylene can be autoclaved, but if you attempt to autoclave polyethylene, you’ll end up with a puddle of plastic.
You should consider temperatures at the opposite end of the thermometer, as well, particularly if you plan to use the labware for freezer storage of samples or solutions. Some plastics retain their protective elastic and impact resistant properties at low temperatures while others become brittle and will likely to crack if they receive an impact. It is the plastic’s brittleness temperature that needs to be considered. Polycarbonate (PC), low-density polyethylene (LDPE) and high-density polyethylene (HDPE) are all good choices for frozen storage as they all have brittleness temperatures below -100oC. Other plastics can be used at freezing temperatures, but care must be taken to protect them from impact to prevent breakage.
Selection tools
Tools are available to help you select the plastic labware that’s best suited to your needs, based on chemical resistance, temperature exposure and other variables. Thermo Fisher Scientific offers a browser-based tool, the “Nalgene Bottle, Carboy and Vial Selection Guide,” for choosing a lab container that is compatible with specific types of chemicals, within a defined temperature range and time period. The tool also lets users indicate their preferred resin; container volume, shape and size; and desirable product certifications (e.g., sterile, low-particulate). These preferences are used to generate a list of containers that meet all the user-defined criteria, whittled down from 677 Thermo Scientific™ Nalgene™ products.
Another helpful tool is the Nalgene “Chemical Resistance Reference Guide,” available as a printed poster and as a download. The chart on this poster displays Thermo Scientific Nalgene products’ resistance to more than 300 chemicals, ranging from acetaldehyde to zinc sulfide. The poster also displays a physical properties chart and product care and use information.
Care and maintenance
After you’ve chosen your labware, you’ll need to care for it to assure its longevity. Be sure to wash pieces thoroughly after use; store items where they will be protected from UV light, including sunlight and fluorescent lighting; and use the labware only with compatible chemicals. Prolonged exposure to UV radiation ages plastic, and exposure to noncompatible chemicals can cause brittleness, severe crazing, stress cracking, loss of strength, discoloration, deformation, dissolution or permeation loss.
When washing, be sure to use a pH-balanced detergent, such as Thermo Scientific™ Nalgene™ L900™ Liquid Detergent. This environmentally friendly formula is biodegradable and nontoxic. When used as directed, it will not cause crazing, cracking or clouding, and it will make labware last longer.
Autoclaving directions and detailed instructions for cleaning Thermo Scientific Nalgene labware—including trace cleaning, general cleaning and removing RNase or DNAase from plasticware—are available online.
Signs of aging
Before each use, inspect your plastic labware for signs of aging, including:
- Discoloration not removed by washing—yellow, brown, orange or pink.
- Brittleness—loss of flexibility.
- Crazing—spiderweb cracks.
- Stress cracking—vertical cracks or those along bends or flex points.
- Pitting and other permanent surface blemishes.
To avoid product failure during use, promptly replace labware pieces when they begin to show any signs of aging. Aged plastic eventually becomes brittle, losing its protective elastic properties, and it is more likely to break. And be aware that repeated autoclaving will shorten the life of your labware.
Getting the most value from your plastic labware starts with choosing a high-quality brand, followed by determining the chemical and thermal properties you require. Check out our other bench tip articles for more information the benefits of plastic labware as well as useful tips on choosing plastic labware. Careful selection, teamed with proper care and maintenance, will assure many years of service from your labware.
Image: Courtesy of Thermo Fisher Scientific
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