In our area detect we research and develop new methods and processes for the detection of microplastics.

So far, all analytical methods require time-consuming and complex extraction and sample preparation before the microplastic can be detected. In most water studies, microplastics are examined with plankton nets with a mesh size of about 0.33 mm. (Lindeque et al., 2020 ) Smaller mesh sizes lead to blockages after a short time. In sediment samples, density separation using highly concentrated salt solutions separates floating microplastics from sinking mineral components.

To reduce the number of natural particles and possible false positive results, natural organic substances are chemically decomposed, most often using hydrogen peroxide or potassium hydroxide solutions or, less aggressively, using specific enzymes (e.g. cellulase, protease, chitinase).

It is generally the case that microplastics can be captured in each process step that was not previously present in the sample. It is precisely for this reason that the analytical values ​​obtained must be treated with great caution.
Microplastic particles are identified by their unnatural color (e.g. light blue and multicolored) and / or unnatural shape (e.g. fragments with sharp edges, perfectly spherical), but can easily be confused with other anthropogenic or natural particles (fly ash, particles from street paint, metal vapor, fish scales, ceramic flakes, etc.). The error rate is estimated at 20-70%. (Löder et al., 2015 ) A a more selective method is therefore absolutely necessary in order to reduce or avoid sources of error and to obtain more precise data.

In our research approach detect we combine natural and environmental science know-how with analytical application. The goal is to detect and quantify microplastics in a simple process step in order to subsequently remove the microplastics from the water in a resource-efficient, sustainable and verifiable manner.
The monitoring of microplastics is divided into sampling, sample preparation and detection. In most aquatic studies, microplastics are sampled with plankton nets with a mesh size of approx. 0.33 mm. Smaller mesh sizes lead to clogging after a short time. Particles that are smaller than the mesh cannot be captured and measured. In sediment samples, floating microplastics are separated from sinking mineral components by density separation with highly concentrated salt solutions. Natural organic substances are broken down through the use of specific enzymes or oxidizing agents.

Despite the complex processing, not all natural organic particles can be separated from the microplastic. A Fourier Transform Infrared (FT-IR) or Raman spectroscope equipped with a microscope or a pyrolysis gas chromatography with mass spectrometer is used for the reliable chemical identification of microplastics. Fragments of common plastics with a diameter of only 20 μm have already been measured by means of spectroscopic analyzes. However, repeated attempts are often required to obtain reliable spectra of very small and weathered plastic particles. In addition, all three methods require very expensive instruments and are very time-consuming.
In addition, all three methods require very expensive instruments and are very time-consuming. In addition to spectroscopic methods, a quantitative differential coloring approach based on the lipophilic dye nile red is used. Microplastics in surface water samples can be marked with the lipophilic dye nile red under a microscope and detected via its fluorescence. (Shim et al., 2016)

New approaches in this area deal with polymer-specific interaction analyzes. These are scientifically based developed, tested and validated directly in relation to the application.

A quick test for microplastics in particular would be helpful for simple, cost-effective process control, especially in an industrial context, in order to make processes even more efficient and at the same time protect the environment.