Christian Piechotta

Bisphenol A (BPA) release from polycarbonate (PC) samples representative for major outdoor applications under environmentally relevant conditions has been characterized by a recently developed artificial accelerated weathering method. It simulates typical environmental stressors through controlled exposure to UVA radiation, rain, temperature, and humidity variations in a weathering chamber. The weathering chamber was modified to a closed-loop water cycle, enabling detection of potential accumulated BPA releases from the investigated samples at ultra-trace levels and excluding contamination. Four PC materials, representative of major outdoor applications, were investigated: (i) Reference PC with low UV absorber content, (ii) coextruded PC sheet with a high UV-absorber content surface layer, (iii) UV-cured coating protected PC for automotive headlamps, (iv) thermally cured polysiloxane hard-coated PC sheet. The artificial weathering tests resulted in consistently low accumulated BPA releases of at most 0.34 mg m⁻² for samples with exposed PC surfaces. Samples with outer surfaces protected by commercial coatings revealed approximately two orders of magnitude lower releases, with cumulative BPA releases of 0.005 mg m⁻² for the UV-cured coating-protected PC and 0.003 mg m⁻² for the polysiloxane hard-coated PC. Across all cases examined, the release of BPA ceased after at most four to six weeks, corresponding to roughly 1–1.5 years of outdoor exposure in Central Europe if correlated based on applied UV radiation dose. Extended weathering for up to 11 weeks confirmed that no further BPA releases occurred after cessation. These results suggest that BPA releases from outdoor PC applications occur only during an initial weathering period and subsequently diminish to virtually zero. The observed release pattern can be plausibly explained by hydrolysis at the PC surface initially triggering minimal BPA releases, while progressive photo-degradation transforms the chemical composition in the topmost surface layer, which is hypothesized to cause the observed cessation of BPA releases.

Bisphenol A (BPA) has been listed as a substance of very high concern (SVHC) due to its endocrine-disrupting properties according to REACH in 2017. European competent authorities have prepared a REACH restriction proposal to reduce BPA levels in the environment. The proposed limit for the concentration of free BPA and other bisphenols in articles is 10 mg kg⁻¹. If exceeded, migration testing can demonstrate that no more than 0.04 mg L⁻¹ is released from the product or material over its lifetime. German authorities are drafting a new restriction proposal after the original was temporarily withdrawn. The residual and migration limits mentioned above were key requirements from the previous restriction proposal. Numerous national and international standards exist for assessing how environmental factors affect the physical and chemical properties of products and materials—such as notch impact strength and tensile strength—but these standards do not cover the release of pollutants. A standardised procedure that covers all aspects of artificial weathering and monitors the subsequent release of pollutants is necessary, especially in the context of the regulation of these substances. An accelerated weathering procedure was established for non-protected samples. This material was not intended for outdoor applications. The testing procedure applied a typical weathering scenario that represents Central European climate conditions. The procedure was validated and applied to samples under distinct quality assurance aspects. Released BPA is quantified via an organic isotope dilution LC-MS/MS method. In parallel, identical samples were weathered outdoors on a weathering rack. Haze and yellowness index are measured to compare outdoor and weathering chamber results.

Since the 1950s, Warfarin has been used globally as both a prescription drug and a rodenticide. Research has shown that warfarin and other rodenticides are present in the environment and food chain. However, emerging contaminants are subject to degradation by biotic and abiotic processes and advanced oxidation processes. In some cases, detecting the parent compound may not be possible due to the formation of structurally changed species. This approach aims to identify hydroxylated transformation products of warfarin in a laboratory setting, even after the parent compound has undergone degradation. Therefore, the Fenton reaction is utilized to insert hydroxylation into the parent compound, warfarin, by hydroxyl and hydroperoxyl radicals generated by Fe²⁺/Fe³⁺ redox reaction with hydrogen peroxide. Using multiple reaction monitoring, a GC–MS/MS method, incorporating isotopically labeled reference compounds, is used to quantify the expected derivatized species. The analytes are derivatized using trimethyl-3-trifluoromethyl phenyl ammonium hydroxide, and the derivatization yield of warfarin is determined by using isotopically labeled reference compounds. The method has a linear working range of 30 to 1800 ng/mL, with detection limits ranging from 18.7 to 67.0 ng/mL. The analytes are enriched using a C18-SPE step, and the recovery for each compound is calculated. The Fenton reaction generates all preselected hydroxylated transformation products of warfarin. The method successfully identifies that 4′-Me-O-WAR forms preferentially under the specified experimental conditions. By further optimizing the SPE clean-up procedures, this GC–MS-based method will be suitable for detecting transformation products in more complex matrices, such as environmental water samples. Overall, this study provides a better understanding of warfarin’s degradation and offers a robust analytical tool for investigating its transformation products.

As a drug and rodenticide, warfarin is used globally. Extensive research has shown that warfarin and other rodenticides are recoverable in the environment and food chain (Fernandez, Santos, Cancela, Laize, & Gavaia, 2014; Gomez-Canela, Barata, & Lacorte, 2014; Nakayama, Morita, Ikenaka, Mizukawa, & Ishizuka, 2019; Rattner, Lazarus, Elliott, Shore, & van den Brink, 2014; Saito-Shida, Nemoto, Matsuda, & Akiyama, 2016; Waddell, Poppenga, & Drobatz, 2013). Current methods for their analytical determination focus on the target component rather than on metabolites or transformation products. Warfarin's phase 1 metabolism is extensively studied. Mono-hydroxylated metabolites are primarily formed (Watanabe et al., 2015; Wong & Davis, 1989). In this study, the use of the Fenton reaction aimed to generate mono-hydroxylated transformation products in the laboratory. A GC-MS/MS method was designed to quantify the expected derivatized metabolites by multiple reaction monitoring. Warfarin, 4'-, 5-, 6-, 7-, and 8-hydroxy warfarin, and isotopically labeled reference compounds were used for this approach. The method has a linear working range of 30 to 1800 pg/µL. Detection limits obtained range between 18.7 to 67.0 pg/µL. In addition, a C18-SPE step was used to enrich the analytes, and the recovery for each compound was calculated. The derivatization yield of warfarin for in-liner derivatization with m-TFPTAH was determined as well. The method was used successfully to show that 4'-O-Me-WAR is preferentially formed under the given experimental conditions. Furthermore, the Fenton reaction has generated all preselected mono-hydroxylated transformation products. The maximum intensities of all target analytes were reached at around 4 minutes and immediately decreased after that. The applicability of GC-MS for determining known metabolites of warfarin was demonstrated. With SPE clean-up, the method is also suitable for detecting metabolites in more complex matrices, for example, environmental water samples in the future.

The potential release of hazardous substances from polymer-based products is currently in the focus of environmental policy. Environmental simulations are applied to expose such products to selected aging conditions and to investigate release processes. Commonly applied aging exposure types such as solar and UV radiation in combination with water contact, corrosive gases, and soil contact as well as expected general effects on polymers and additional ingredients of polymer-based products are described. The release of substances is based on mass-transfer processes to the material surfaces. Experimental approaches to investigate transport processes that are caused by water contact are presented. For tailoring the tests, relevant aging exposure types and release quantification methods must be combined appropriately. Several studies on the release of hazardous substances such as metals, polyaromatic hydrocarbons, flame retardants, antioxidants, and carbon nanotubes from polymers are summarized exemplarily. Differences between natural and artificial exposure tests are discussed and demonstrated for the release of flame retardants from several polymers and for biocides from paints. Requirements and limitations to apply results from short-term artificial environmental exposure tests to predict long-term environmental behavior of polymers are presented.