A Time-Gated Raman Spectroscopy and Mass Spectrometry Comparative Chemical Analysis of Plasticizers

Quantitative chemical characterization of postconsumer plastics is challenging because of the large number of polymer chemistries and additives used in formulating plastic products. Plasticizers are an important family of additives used to lower the glass transition temperature and enhance flexibility in polymer formulations. However, their identification and quantification are difficult in recycling and end-of-life processes. This study critically assesses two analytical techniques for their suitability in plasticizer identification: mass spectrometry (high resolution, selectivity, and sensitivity) and time-gated Raman spectroscopy (nondestructive, quicker, and minimal sample preparation). Here, we generate searchable libraries for the identification of 91 common plasticizers using these two techniques, along with the development of reliable tools to measure their spectral similarity. We then analyze the reliability of identifications based on time-gated Raman and/or liquid chromatography-mass spectrometry with atmospheric pressure chemical ionization, explicitly highlighting the advantages and disadvantages of each technique for a given plasticizer chemical family. We have applied these tools to identify and quantify plasticizers in a NIST Standard Reference Material (SRM 2860, Phthalates in Polyvinyl Chloride).