Determination of nucleating agents in plastic materials by GC/MS after microwave-assisted extraction with in situ microwave-assisted derivatization

This work demonstrates the analysis of sorbitol-based nucleating and clarifying agents (NCAs) used as additives for polyolefin-based materials by gas chromatography/mass spectrometry (GC/MS), employing a highly reliable and efficient sample preparation methodology applying microwave irradiation. A derivatization by silylation of the analytes was done to improve the GC-suitability of the analytes. After successful optimization of the conditions for a microwave-assisted derivatization (MAD), the microwave-assisted extraction (MAE) of the analytes from polymer samples was investigated. Tetrahydrofuran (THF) turned out to be the best extraction solvent, as poorly soluble analytes show the highest solubility in this solvent and THF supports the silylation after extraction. This two-step approach and subsequent chromatographic determination resulted in reproducibilities from approximately 2% up to 6% and recoveries from 95.8% up to 104.2% in real samples. In order to reduce the number of sample preparation steps a one-step approach was investigated and optimized, in which MAE and MAD were carried out simultaneously. The developed procedure resulted in remarkably better repeatabilities ranging from 0.05% up to 4% and reproducibilities of up to 10%. The recoveries matched those obtained with the two-step process. Linearities could be achieved in both approaches with R-2 better than 0.99 for all selected analytes over two orders of magnitude. All data indicate the suitability of both presented methods for the reliable determination of sorbitol-based NCAs in polyolefin materials. (C) 2014 Elsevier B.V. All rights reserved.