Integrated size- and composition analysis of nanoplastics by hyphenating hydrodynamic chromatography to pyrolysis-gas chromatography-mass spectrometry

To understand the health impact of micro- and nanoplastics (MNPs), methods to quantify the levels of the various particle size ranges as well as techniques to chemically characterize them are needed. Current analytical strategies largely focus either on the size or the chemical composition of these MNPs, without correlating the two. A novel hyphenated method is presented that combines hydrodynamic chromatography (HDC) with pyrolysis-gas chromatography-mass spectrometry (Py–GC–MS) for integrated size- and composition characterization. Because HDC does not use membranes or stationary phases, the need for mobile phase additives is significantly reduced, simplifying combination with Py–GC–MS identification. In the newly developed method, the effluent of the HDC size separation is fractionated and individual fractions are subjected to Py–GC–MS identification. Introduction of the fractions and subsequent pyrolysis is done using a programmable temperature vaporization (PTV) inlet. The PTV introduction step employs a three-stage temperature program: an initial low-temperature hold for water removal, followed by an additive-removal step at moderate temperature, and finally a treatment at high temperature to pyrolyze the MNPs. The PTV Py–GC–MS method showed a good performance in the analysis of various plastics including PET, PA12, PTFE, PTHF and PE. For other plastics like PAN, PVDC and PVC the identification capability of the method was also good, but quantification was compromised by partial losses of the material during additive removal. Application of the HDC–Py–GC–MS method to a PS nanoplastic mixture, as well as to a representative industrial acrylate/styrene nanoplastic sample, highlighted the method’s potential for correlating size and chemical composition.