Development of an LC-MS method for the semiquantitative determination of polyamide 6 contaminations in polyolefin recycl
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RESEARCH PAPER
Development of an LC-MS method for the semiquantitative determination of polyamide 6 contaminations in polyolefin recyclates Andrea Schweighuber 1 & Markus Gall 2 & Jörg Fischer 2 & Yi Liu 3 & Hermann Braun 3 & Wolfgang Buchberger 1 Received: 23 September 2020 / Revised: 9 November 2020 / Accepted: 13 November 2020 # The Author(s) 2020
Abstract Recycling will be of increasing importance in the future, especially for plastic packaging waste mainly consisting of polyolefins. One major problem of recyclates comprises impurities which can have a significant negative impact on future product properties. Polyamide 6 can be found widely as contaminant in recycled polyolefins, leading to a need of quantification methods thereof. In this paper, a method development for the quantitative analysis of polyamide 6 is presented based on analysing ε-caprolactam and related cyclic oligomers as marker compounds in model recyclates of high- and low-density polyethylene and polypropylene compounded with low amounts of polyamide 6. For the method development and tentative identification of the different cyclic compounds, a HPLC-QTOF-MS was used and it was possible to detect six different compounds, ε-caprolactam and the corresponding cyclic di- to hexamer. The quantification was performed with a HPLC-QQQ-MS, equipped with a HILIC column, after sample preparation via microwave-assisted extraction. It could be shown that a good linearity from 0.2 up to 5 wt% polyamide 6 in the different polyolefins can be achieved. The cyclic trimer and tetramer show a low limit of quantification and are therefore well-suited for the quantification, whereas the other cyclic compounds can be then used as qualifiers to avoid false positives. To guarantee the applicability of the method, six real recyclate materials were analysed, whereby in three of them low amounts of polyamide 6 could be detected. Keywords Polyolefins . Recyclates . Polyamide contamination . Liquid chromatography . Mass spectrometry
Introduction In the recent decades, the importance of plastic packaging waste recycling has grown rapidly since the amount of generated waste increased by 19% from 2006 to 2018 in the European Union (EU), leading to a total of 17.8 million tons in 2018. Thereof, 42% were recycled, 39.5% were used for energy recovery and 18.5% were disposed at landfills [1]. To rise the share of recycling, the EU
* Andrea Schweighuber [email protected] 1
Institute of Analytical Chemistry, Johannes Kepler University, 4040 Linz, Austria
2
Institute of Polymeric Materials and Testing, Johannes Kepler University, 4040 Linz, Austria
3
CES – Circular Economy Solutions – Innovation & Technology, Borealis Polyolefine GmbH, 4021 Linz, Austria
legislated the Directive (EU) 2018/852, regulating minimum plastic recycling quotas of 50% by 2025 and of 55% by 2030 respectively [2]. Mechanical recycling is the main recycling technique, including the steps separation, washing, melting and processing. A crucial part herein belongs to the sorting in order to gua
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