Labware - breaking the glass habit

It might be the trusty servant of all scientists, but there is an alternative to the breakable glassware found in the lab

As a part of any laboratory, labware such as beakers, cylinders, funnels, flasks, bottles and carboys, can have great impact on an experiment. With the ability to influence the integrity of resulting data, as well as the safety of personnel, it is vital that careful consideration is given to the selection of labware. As a component of the lab that is often taken for granted, researchers trust these containers with their valuable samples and solutions on a daily basis. But not all are created equally and there is the potential that some actually threaten the integrity of downstream data, with extractables that can compromise research, in some cases rendering results unusable. As such, the labware chosen to enter any workflow should be selected with great care and consideration.

With daily routines comes a certain degree of bumping and knocking that is unavoidable, and in such instances, the labware can also be knocked over, dropped or subjected to an unsteady hand. Thus, these containers need to be composed of a hardy material that is able to absorb shock, rather than break.

Most labware has traditionally been composed of borosilicate laboratory glass. Although adequate function is provided by such materials, there are potential issues that could arise. Glass is a fragile material and is easily broken. While this can be catastrophic in terms of valuable solutions being lost and hazardous materials being released, the act of breakage could also result in shards of glass flying across a busy laboratory space – creating a hazard to personnel within the surrounding environment. If glass labware simply cracks or chips, repair may be possible, but can be costly. If not fixed or replaced, exposed sharp edges can pose an additional hazard.

As a viable alternative to glass, plastic is fast becoming the material of choice for labware. Not only is it less likely to shatter, but the variety of high-quality plastic resins enable users to select a piece that is best suited to their application requirements. Furthermore, with ‘green’ becoming a growing theme throughout industry, it is important for all environmentally-friendly aspects to be taken into account. While glass is generally thought of as recyclable, the borosilicate glass used in the manufacture of glass labware is not, due to its heat-resistant properties. However, plastic alternatives are reusable and extremely durable, reducing the waste of disposable containers. An economical manufacturing practice in combination with the ability to recycle and reuse the containers themselves, proves to be a highly ecological workflow.

Laboratories are often small, busy spaces, making movement between equipment difficult and tight. This movement, in combination with the potential jostling of several containers in a single unit, increases the chance of breakage. Plastic is a lighter, more robust and shock absorbent material than glass, and more likely to crack than shatter upon mechanical stress, reducing the possibility for injuries. Additionally, if a plastic container is dropped, it tends to bounce rather than break, preventing the loss of valuable reagents and solutions, while avoiding a spill of potentially hazardous or infectious solutions.

Although plastic is the safer choice in terms of durability, different manufacturers will incorporate a variety of characteristics when developing their plastic labware. One critical point in ensuring safety is to purchase a bottle with an adequate closure seal to prevent spillages. By using a strong semi-buttress thread design and valve seal, bottles and carboys can be guaranteed leakproof without the use of a cap liners that can corrode, fall out or wrinkle causing leakage. As a result, when stored long-term, for example in a refrigerator or freezer, users can be safe in the knowledge that substances and solutions will not have leaked and adversely affected any other samples. In the production of Thermo Scientific Nalgene bottles and carboys, closures are selected at random for quality control testing throughout the production process. Standard test bottles are filled with water and the closures applied at specific torque values. An air pressure of 2 psig is applied for two minutes and then released. The closures are removed and inspected, and if no water is found on the closure or bottle threads then the closures are judged leakproof (this protocol applies to closures of 83mm or smaller). The same procedure is applied during bottle production to ensure a leakproof sealing system is achieved.

Plastic resins for laboratory use must be selected to minimise additives and reduce potential leachables to ensure the composition of the labware has no impact on the samples or reagents that it contains. Since plastics contain far lower concentrations of trace element extractables than glass, they can be used in more sensitive applications, such as trace metals analysis. There are a broad range of plastic resins to choose from, each with differing properties and benefits, as listed in table 1.

• Polyolefins are high molecular weight hydrocarbons, including low and high density polyethylene (LDPE/HDPE), polypropylene copolymer (PPCO) and polypropylene (PP). All are break-resistant, nontoxic and non-contaminating. They easily withstand exposure to nearly all chemicals at room temperature for up to 24 hours. However, strong oxidising agents eventually cause them to become brittle and all polyolefins can be damaged by long-term exposure to UV light.
• Engineered resins offer exceptional strength and durability in demanding applications. These include polyethylene terephalate G copolymer (PETG/PET) and polycarbonate (PC).
• Specialty resins such as thermoplastic elastomer (TPE) can be moulded into autoclavable parts which are rubber-like in application and performance.
• Fluorocarbon resins have remarkable chemical resistance. Perfluoroalkoxy (PFA) has a low co-efficient of friction, outstanding anti-stick properties and is flame-resistant, while fluorinated ethylene propylene (FEP) can even be boiled in nitric acid. Ethylene-tetrafluoroethylene (ETFE) shares the remarkable chemical and temperature resistance of FEP, but has even greater mechanical strength and impact resistance.

Table 1: Resin reference chart

 

 

 

 

 

 

 

With a range of resin certifications for laboratory, food and pharmaceutical use, an online resin selection tool (available at www.thermoscientific.com/nalgenecontainers) aids users in choosing the optimal container for each application.

With critical importance to sensitive applications requiring the containment of solutions such as pharmaceutical active ingredients or ultra-high purity solutions, resins often need to be validated in-line with various regulatory specifications, including:

• The United States Pharmacopeia (USP) Class VI
• European Pharmacopeia Standards
• Food and Drug Administration (FDA)
• The Coalition of Northeast Governors (CONEG)
• California Proposition 65 – a Californian Law which protects drinking water sources from toxic substances that cause cancer and birth defects and to generally reduce or eliminate exposures to those chemicals. It is administered by Cal/EPA's California Office of Environmental Health Hazard Assessment (OEHHA)

Each container needs to be clean prior to use. As a subjective descriptor, ‘clean’ can mean different things to different people. In a general laboratory setting, clean may simply mean washed with soap and water and rinsed with deionised water.  In a microbiology or cell culture lab, common use of the term might mean that the container is sterile. In a trace analysis or biotech lab, clean may also mean low in particulates, with no detectable trace elements of contaminating compounds. In order to ensure individual expectations are met, it is important to understand how the plastic labware or container is manufactured and processed. For example Thermo Scientific Nalgene containers are available with a variety of clean certifications:

• Certified clean PETG containers are manufactured in a clean room certified to the ISO 14644-1 Class 7 Standard. Containers are also lot-to-lot tested and certified using liquid particle count analysis. These containers are certified non-cytotoxic, non-pyrogenic, non-hemolytic and sterile. By following ANSI/AAMI/ISO 11137 guidelines in establishing an irradiation dose level to support a sterility assurance level (SAL) of 10-6, these containers are ideal for processing and storing critical reagents and bulk intermediates such as vaccines and protein therapeutic preparations.

• Low particulate and low metals certified bottles are manufactured in a general factory environment and processed by a secondary wash to achieve a particulate level of <20 particles/mL at 0.3 µm and greater. Each bottle is double bagged under Class 10 laminar flow hoods inside a Class 10 clean room and a certificate of analysis supplied with each case shipped. These bottles are therefore excellent for high purity chemical storage and ICP-MS reagent and standard storage.

• •    HDPE low particulate bottles are manufactured in a controlled environment and are lot certified to contain <30 particles per mL at 0.3 µm and greater. Each lot is tested and certified using liquid particle count analysis. These bottles can be used in compliance with the regulations for customers who are designing, assembling and certifying their own combination packaging system.

Unlike glass labware, there is an extremely broad variety of plastic containers available, all composed from different resins and optimised for use in a range of applications. Selecting the best plastic for your usage may become a daunting prospect. Only purchase plastic bottles and other labware from a reputable source; some plastics are loaded with additives that can leach into the lab reagents, causing contamination and compromising the integrity of experimental set-ups.

• Look for products made from USP Class VI compliant resins. These have been tested for biological toxicity. In addition, this certification is a good indication of high purity resin use
• Look for suppliers who use pharmaceutical and food grade resins containing minimal additives
• All plastics contain some amount of additives, in the form of antioxidants and heat stabilisers that make plastic mouldable. Lab plastics should however contain the bare minimum necessary, and unnecessary additives like clarifying agents, colorants, fillers, extenders and plasticisers should be avoided
• Avoid any plastics with an oily film on the surface as this is most likely mould release or slip agents which have been added to the resin to make it easier to mould. These types of additives can contaminate solutions: washing will not eliminate this effect as they can continually leach to the surface.

Labware is an essential component in all laboratory workflows, but its importance is often overlooked. With implications to the integrity of resultant data and lab personnel safety, there are many advantages of using plastic instead of glass. However, glass is still in wide use today where it would be suitable and advantageous to substitute plastic. In terms of safety, the more environmentally-friendly option of plastic is slowly coming to the forefront, with many offering leakproof and shatterproof guarantees. With high purity resins, there is a suitable container available to meet nearly any requirements. All you need to do is simply break the glass habit and make the switch to plastic.

Author: Lorie Croston, Thermo Fisher Scientific