Tackling the Microplastics Issue: Identifying Microplastics with the GERSTEL Pyrolyzer in Combination with Gas Chromatography

In recent years, plastic has transitioned from a versatile material in the public’s eye, used for a variety of applications, to a global issue with alarming consequences. Plastic that fails to be disposed of properly is affecting our marine ecosystems and the wildlife that resides there in a very serious way. The presence of all plastic in the world’s oceans is cause for concern for the health of our marine life, but the most alarming problem lies in the issue of microplastics.

Plastics, micro- and nanoplastic pollution in oceans, lakes and other water sources is a well-documented issue. Uptake of these particles by shellfish and fish is one avenue for the pollutants to enter the food chain and cause possible adverse effects. Micro- and nanoplastics are commonly used in commercially available products as abrasives. They end up in the environment from down the drain disposal, and subsequently are not efficiently removed in the wastewater treatment process.

Solving the microplastic crisis will not be an easy feat. With the size of the plastic particles, potential removal methods are difficult to execute. However, the problem simply cannot be ignored and the first step in solving the microplastic crisis is to identify what microplastics are present in bodies of water around the world. Technology from GERSTEL can provide the means necessary to take this first step and provide scientists with solutions to begin tackling the microplastic issue.

The GERSTEL pyrolyzer in combination with gas chromatography mass spectrometry, performed the identification of plastic pollution samples collected from the Great Lakes. Additionally, in a second application, the GERSTEL pyrolyzer was used to efficiently identify pollutants in personal care products.

The GERSTEL Multipurpose Sampler (MPS) in combination with the GERSTEL Thermal Desorption Unit (TDU 2) and programmable temperature vaporizer (PTV) inlet, the CIS 4, provides users with a multitude of analytical options to utilize for sample analysis. The TDU PYRO offers efficient automation and a variety of modes including standard pulsed, sequential and fractionated pyrolysis. The CIS 4 can be used to cryofocus analytes in the inlet or be used as a hot split interface for direct transfer to the column.

To read the full story, please download our application note “Determination of Microplastics using Pyrolysis Gas Chromatography Mass Spectrometry.”

Simplified Method Development:

Flash pyrolysis GC-MS usually consists of running several pieces of the same sample at different pyrolysis temperatures and evaluating the chromatograms for secondary pyrolysis products. This is done in order to choose the optimum pyrolysis temperature for the sample. This can be a time-consuming process and not practical when the amount of sample is limited.

Smart Ramped Pyrolysis (SRP) mode uses a temperature ramp of 5 ºC/s from 300 ºC to 800 ºC. The slow temperature ramp, relative to pulsed pyrolysis, avoids the formation of secondary pyrolysis products. This mode produces chromatograms similar to those obtained using an optimized pulsed temperature. The result is the need to only run a single sample to achieve an optimum pyrogram.

Plastic (netted) and sediment samples from the Great Lakes were analyzed. The sediment samples were aqueous with suspended strands and particles. The plastic samples were non-homogenous plastic particles. The plastic samples and sediment samples were analyzed using SRP mode.

The results showed that the netted samples were composed of mainly polyethylene (PE), polypropylene (PP) and mixed PE/PP. The sediment sample pyrograms showed a mixture of compounds including styrene, methyl methacrylate, siloxanes, phthalic anhydride and a plasticizer bis(2-ethylhexyl) phthalate.

Microplastics in the environment can come from several sources including tires, marine coatings, dust, plastics, and personal care products, among others. Personal care products which contain microplastics include toothpaste, facial cleaners, scrubs, wipes and bath products.

Pyrolysis GC-MS was used to analyze a commercial facial wash product for microplastics. Fractionated pyrolysis, at 120, 300 and 600 ºC, was used to analyze this sample, Figure 1. Fractionated pyrolysis helps to simplify the chromatograms, making analysis of the sample easier. In the top chromatogram (at 100 ºC), a large glycerol peak is present which is added to the product to increase skin smoothness and aid in moisture retention. 1,3-butanediol is a skin conditioner and stabilizer, 2-phenoxyethanol is added as a preservative and the long chain acids are added as moisturizers and anti-microbial agents. The middle chromatogram (at 300 ºC), shows more of the long chain acids along with long chain amides, used as emulsifiers, siloxanes and sulfur dioxide. Sulfur dioxide can be a thermal degradation product of dextran sulfate which is commonly added to cosmetics as a binder/skin conditioning agent. The bottom chromatogram shows a pattern for polyethylene, most likely from beads added as an exfoliant.

In conclusion, the GERSTEL MPS Robotic/TDU/CIS with the TDU PYRO module can be used for the identification of microplastic samples from the environment or commercial products. Smart Ramped Pyrolysis mode can be used in order to simplify methods development, especially for unknown samples and where a sample may be limited. Fractionated pyrolysis can be used in order to simplify a complex chromatogram and identify microplastics in commercial products.