Plastic versus glass in the lab

Plastics are now a viable alternative to glass for containers in the laboratory, not least for their resilience to breakage and low extractable profile.

The ergonomic benefits of plastic lab containers make it a practical and economical choice

Conventional wisdom was that glass and steel containers were the only viable options for pharmaceutical labs. Lorie Croston Product Manager, Labware and Specialty Plastics, at Thermo Fisher Scientific argues, this dynamic has changed and plastics have become a material of choice for drug development.

Scientists have ever-increasing demands for high-quality, versatile and durable containers that will advance their research from the beginning of the drug discovery process through formulation, processing and packaging. New types of non-cytotoxic resins that are now being used in plastic labware do not interact with biological life forms and have extractable and leachable profiles designed for lab use. In many instances, these new state-of-the-art resins are a preferred choice compared with glass.

Many lab personnel do not realise that glass has a high extractable profile, due to its core component, sand, which can vary greatly from one container to the next. The composition of glass can change significantly based on its country of origin; usually China, India or the US. This was particularly true of glassware manufactured after the 2004 tsunami in the Indian Ocean, which significantly impacted local sand composition and caused a higher level of extractables in the glassware produced in this region. Depending upon its manufacturing source, glass lab products can leach ionic compounds, which can affect the consistency of highly valuable pharmaceutical samples.

In the past, glass and steel containers were the only viable options for scientists throughout the production process, limiting workflow at critical stages because of breakage, loss of valuable sample, cost of repairs or the need to replace the container. Advancing protocols require that labs choose non-cytotoxic and sterile containers that are also resilient, leak-proof and have validated consistency of manufacturing materials.

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Plastic is easy to move, strong, lightweight and shatterproof. Plastics are resilient and able to absorb more shock when bumped or dropped providing the benefits of greater safety for scientists, reduced potential for loss of valuable sample and decreased costs for container replacement or lost time due to personnel injury.

Although it provides adequate function, glass is heavy and breakable. Carrying large flasks and cylinders of solutions in glass is cumbersome, especially in busy labs with many users.

The ergonomic benefits of plastic lab containers make it a practical and economical choice. The use of lightweight plastic containers means reduced delivery costs, an increasingly important factor in the drug manufacturing scale-up process. In an automated lab using robotics or requiring a high throughput, a lighter plastic container is shock absorbent if mechanically stressed, reducing the cost of halting research or the scale-up process because of leakage or shattering of glass containers.

Not all labware is created equal and there are important selection criteria to consider: Look for plastic containers that incorporate a variety of features to provide a “leak-proof” guarantee. For example, consider selecting bottles with certified closure seals that are guaranteed to be leak-proof. Leakage may occur with long-term storage in refrigerators or freezers from poorly manufactured closures or containers. Leak-proof plastic containers are manufactured with precise moulding of the bottleneck area and a consistent wall thickness to ensure a tight seal, guaranteeing the security of the sample.

Some types of cap liners can corrode or fall out, so consider choosing containers made with a strong thread design and a valve seal in the neck area. The manufacturing process of the container is equally critical, including leak testing of containers via pressure analysis as part of QC to assure a leak proof sealing system.

There are many types of plastic containers manufactured from different grades and qualities of resin, and chemists and management need to make informed decisions about which type of material to choose. The plastic they select must be made from resins that minimise additives and reduce potential leachables, ensuring that the composition of the container has no impact on the samples or reagents it contains.

Plastics are resilient and able to absorb more shock when bumped or dropped

Make sure to request resin information/data that support pharmaceutical manufacturing during the validation process. Resin validation also enables scientists to work in compliance with regulatory standards.

For chemists working in drug discovery through the complete manufacturing chain, it is highly recommended to purchase plastic containers made from US Pharmacopeial Convention Class VI compliant resins. These have been tested for biological toxicity and include pharmaceutical and food grade resins with minimal additives, such as slip agents or fillers, which can often be used in the lower grade plastics manufacturing process.

Highly useful online resin selection tools and mobile apps guide users who need to choose an optimal container for a variety of different applications. These apps offer easy, 24 hr access to labware products and solutions. Sensitive applications requiring the containment of solutions such as active pharmaceutical ingredients (APIs) or ultra-purity solutions require resins that are validated in-line with various regulatory specifications including:

  • The US Pharmacopeia (USP) Class VI
  • European Pharmacopeia Standards
  • Food and Drug administration (FDA)

It is important for manufacturers to validate that the plastic composition has remained consistent from drug discovery through processing to market. Undergoing the validation process for plastic, glass or steel containers that are intended for storage of APIs is a costly and lengthy process, often taking up to two years.

Look for vendors that provide registries or databases, ensuring that drug manufacturers will be notified in the event that a resin is changed in the type of plastic containers they have selected for research or scale-up production processes.

Containers used in production can vary in capacity from 50 to 2000 litres. A benefit of using plastic containers is that the composition of the material does not change even though the container size might. Once the resin has been validated in one size, the validation holds for many other size variations. This is not the case with glass. Because of the variable nature of its core component, each new size of container must be re-validated, making glass a much less scalable material than plastic.

Safety is always a concern when considering the risk of glass containers shattering in the lab setting. Not only is this a health and safety hazard, it can also be expensive if glass containers are holding valuable APIs. Plastic labware, including beakers, cylinders and funnels will not shatter or break like glass, making them a safer alternative in the lab.

Most plastic lab containers are recyclable and reusable. Traditional glassware made from borosilicate glass has heat-resistant properties that make it non-recyclable. Some recyclable polyethylene resins have become part of highly ecological workflows by reducing the waste of disposable containers. The durable properties of plastic also have the benefit of easy cleaning and reuse when reuse is approved, as plastic labware can be washed without worry of cracking or breaking in the busy lab sink environment.

Despite the multiple benefits associated with using plastic labware, it is important that chemists make informed decisions about the materials best suited to their application. This is because there are many different types of plastics with varying physical and chemical properties, all of which are useful for different applications and solvents.

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