Glass VS. Plastic in the Lab

Glass vs Plastics in the Lab

Glass has been a key material in the lab for centuries. Glass containers can be heated with flame or frozen. Perfectly transparent, it can be molded into flasks, cylinders,burets, beakers and bottles.

In the modern lab, glass is the only material used for “Class A” volumetric benchware. Glass is also valued for its optical properties and permeability:

Glass can be shaped so that it refracts light into the varying wavelengths of the light spectrum. Spectrophotometers, refractometers, and traditional microscopes, for example, take advantage of this property.

Most pH electrodes and ion specific electrodes are made of glass engineered to permit the penetration of just one ionic species. These electrodes can be extremely accurate. In a nuclear power plant, corrosion of the turbine blades is of great concern. They use a sodium electrode capable of detecting less than one PPB (parts ber billion)

Glass has several disadvantages, of course. It breaks and when it does, it shatters into sharp slivers. In fact, worker protection rules gave birth to plastics in the lab. Back then Nalge Company came up with a trade show give-away which was a box of Bandaids with the slogan “Break the Glass Habit”.

Another disadvantage is that glass can either absorb ions from a sample or contribute ions to a sample , which is a problem in trace metal analysis. That’s why the EPA, when testing for mercury in the PPB level in a lake, won’t accept results from a sample delivered to the lab in a glass container. I-Chem, another Thermo company, make glass bottles coated with a flouropolymer inside so as to make sure the container neither contributes nor absorbs the ionic species of interest.

These days plastics are valued by many scientific disciplines for a host of other reasons besides the fact that it does’t break. As plastics engineers developed new polymers, many were found to have applications for the lab based on the unique characteristics of the new polymer.

Polycarbonate is so strong that its used in making bulletproof windshields, but it has zero chemical resistance…,strong acids go right through it. Flouropolymers are not nearly as rigid and strong as carbonate but is so chemically resistant that concentrated hydrofluoric acid, which can dissolve glass, is no problem.

Even resins like common polystyrene can be manipulated to meet the needs of the lab. The NUNC company (Nalge-Nunc is a Thermo company) in Denmark uses a patented technique to treat the inner surface of a petri dish so that, rather than a flat surface, the bottom is covered with a forest of tiny spikes. This greatly increases the surface area for cell adhesion in cell culturing applications. Some investigators can make their incubators thewnty time more productive with these dishes.

So really its not Glass vs Plastics in the lab, its Glass AND plastics in the lab.


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