As a practical alternative to glass, plastic is quickly becoming the material of choice in many laboratories. While glass labware has the potential to crack or shatter, affecting the integrity of resulting data, as well as the safety of the scientist, plastic labware is more durable and often more affordable. As the glass-to-plastic conversion rate in the United States increases, it is important for scientists to ensure they are making informed plastic labware choices that match intended usage. This includes selecting plastics based on chemical compatibility, temperature exposure, and sterilization requirements.
All plastic labware must contain a small amount of stabilizing additives that make the plastic moldable; typically heat stabilizers and antioxidants must be present so the plastic does not break down during molding. While critical to the plastic, it is important to be leery of additives and select only the plastic labware that uses the lowest trace amounts necessary. Other, more elective additives include processing aids such as mold release agents, clarifiers, UV stabilizers, and fillers that can make manufacturing cheaper and faster or add additional properties to the plastic.
The benefits of any additive should be weighed against the risk of leaching from the labware and contaminating lab solutions. As a rule of thumb, less is more regarding additives in high-quality lab-grade plastic. The quality of the plastic resin used in producing labware is reflected in the cost of the products, making this a family of products in which scientists definitely get what they pay for. When priceless samples are on the line, it is worth the additional expense to obtain plasticware from a reputable manufacturer, not to mention, it will often still be less expensive than glass.
It is also important to note that container selection is not a consideration reserved just for plastic. Glass labware contains trace metals often at high levels that can contaminate samples, and chemical stress can occur regardless of material composition. The main differences between glass and plastic include that glass is completely oxygen impermeable, while plastics are not, and plastic leachables tend to be organic in nature, while glass leachables are inorganic. While plastic is the best option for impact resistance, glass is the better choice for direct contact with hotplates or use in ovens.
Plastic and glass labware cleaning and maintenance
Procedures for sterilization and cleaning of these two materials are comparable, though care should be taken to choose autoclavable or gamma-stable plastics if those types of sterilization procedures are to be performed. Another benefit of using plastic labware is that scientists are able to wash beakers and containers without fear of cracking or breaking them. Plastics are resilient and able to absorb much more shock when bumped or dropped, so there is less breakage. Less breakage also means greater safety for samples and scientists as well as reduced costs for labware replacement.
The importance of ergonomics
The ergonomics of plastic labware is another consideration that scientists think about when making the switch. Say a scientist is repeatedly filling a large graduated cylinder with a liquid and pouring it into other containers. With glass, the cylinder will be heavy and harder to control and care is needed to avoid bumping the glass against any hard surface. Plastic labware is more lightweight, will not break if it is dropped or bumped, and is easier to handle than glass.
Differences in quality of plastics
Once scientists have made the decision to convert from glass to plastic, there are still decisions to be made. Not all plastic labware is created alike, and it is important for sample integrity to select only the highest-grade plastic resins with minimal additives. There are many manufacturers that lower production costs by adding higher levels of additives in the form of processing aids, which speed up the molding process. Unfortunately, this can increase leachables and negatively impact samples. Two different plastic beakers may look almost alike but contain completely different levels of additives and vastly different qualities of plastic resin.
To make the decision easier, there are plenty of resources that help scientists choose the best plastic labware for their intended purpose. Since plastics differ in wall strength, temperature endurance, radiation stability, and chemical compatibility, it is always a good idea to cross-reference a solid resource, such as a detailed on-line container selection guide. Mobile applications also exist that serve as helpful resources for scientists on-the-go, or who want easy, instant access to a thorough plastic selection guide. One resource, the Thermo Scientific Nalgene Bottle and Carboy Application by Thermo Fisher Scientific (Waltham, MA), is a highly utilized application in laboratories that have converted at least some of their labware to plastics (http://www.thermoscientific.com/ecomm/servlet/newsdetail_11152_54572_-1?ca=nalgenebottleapp).
Because labware is a fundamental element for all successful laboratories, making informed decisions when selecting it is equally important. From ergonomics and cost, to sample and scientist safety, the benefits of the glass-to-plastic laboratory conversion are numerous. Plastic has enhanced shock resistance and lenience to higher centrifugation speeds than glass tubes, which provides further safety for laboratory employees handling the labware. Also, the elasticity of plastic makes it easier to use in an automated robotic laboratory. Scientists and laboratory executives need to pay special attention to these considerations when choosing exactly which labware is best for their lab.
Lorie Croston is Product Manager, Labware and Specialty Plastics, Thermo Fisher Scientific, 81 Wyman St., Waltham, MA 02454, U.S.A.; e-mail: email@example.com.