Simultaneous quantification of microplastic particles by non-deuterated (NoD) 1H-qNMR from samples comprising different polymer types

Facing microplastic contamination and thereby its impacts on the environment and health will probably be one of the most concerning challenges in our immediate future. Yet, data on these emerging pollutants are still scarce in many aspects leading to the ongoing development and expansion of analytical procedures and approaches. In recent years, despite being used formerly only for qualitative aspects, nuclear magnetic resonance spectroscopy (NMR) was introduced for the quantification of microplastic particles. By the combination of linear regression procedures, internal standards and the integration of proton NMR, the so-called qNMR method allows mass-based quantification of microplastics in a limited amount of time and independent of particle size. Based on this approach, further optimization through the simultaneous dissolution and quantification of multiple polymers is investigated. Individual requirements, known issues and considerations will be demonstrated along with additional possibilities for five polymers: polystyrene (PS), butadiene rubber (BR), polyvinylchloride (PVC), polyethylene terephthalate (PET) and polyamide (PA). The applicability of homopolymer-based calibrations is demonstrated for both the quantification of multiple homopolymers dissolved in a shared solvent system and the quantification of copolymers; for example, a styrene-butadiene copolymer (SBR). Linearities and limits of detection and quantification as well as precision and accuracy comparable to those of solely measured microplastic particles are achieved. The improvement significantly reduces the preparation and measurement time in combination with lowered costs. In addition, enhanced reliability was achieved by implementing hexamethyldisiloxane (HMDSO) as an internal standard in NoD measurements, replacing dichloromethane (DCM).