RESUMO
Epoxy resin coatings applied to steel constructions for corrosion protection purposes are often exposed to UV-irradiation and weathering during the construction process. Chemical alteration of the hardened coating might lead to i) the release of potentially harmful substances into the environment and ii) delamination of the polyurethane top layer. However, chemical processes and mechanisms occurring on the surfaces of exposed epoxy resin coatings are not fully understood yet. Herein, we present an innovative approach combining time-of-flight secondary ion mass spectrometry (ToF-SIMS) with inductively coupled plasma mass spectrometry (ICP-MS) and liquid chromatography mass spectrometry (LC-MS) enabling the elucidation of underlying chemical processes and the identification of released organic and inorganic photolytic products. IR-spectroscopy and experiments targeting the acidity/pH-value changes on top of weathered surfaces complement our investigations. It was confirmed that UV-A irradiation leads to photooxidative degradation of the epoxy resin and that inorganic photolytic products are exposed on the weathered surfaces. Polar moieties (hydroxyls, carbonyls, carboxyls, amines) and released metalloids form a hydrophilic surface layer, which hinders adhesion and eventually prevents profound chemical linkage of the polyurethane top layer. Thus, an early delamination of the top layer might occur very likely.
RESUMO
An analytical method based on high resolution mass spectrometry coupled with liquid chromatography (LC-HRMS) for 25 quaternary phosphonium compounds (QPCs) and derived phosphine oxides (POs) was developed and validated. To investigate the occurrence and fate of QPCs in the aquatic environment, water, suspended solids and sediments from the rivers Rhine and Elbe (upper and middle Elbe as well as tidal Elbe) were analyzed, as well as samples from tributaries bearing significant loads of QPCs. For the first time, the quaternary phosphonium compound tetrabutylphosphonium (Bu4P+) was detected. In the river Elbe concentrations were determined of up to 4700 ng/L (surface water) and 1000⯵g/kg (sediment), respectively. Analysis of a time series of suspended solids (2005-2015) showed that QPCs have been present in the Elbe and Rhine catchment for at least one decade, with partly rising tendency. A degradation experiment with Rhine sediment revealed that triphenylphosphonium compounds (R-Ph3P+) and Bu4P+ are persistent in contact with sediment and suspended solids and tend to sorb onto sediment particles. Toxicological studies (reactive oxygen species (ROS) after substance exposure, Ames test, Micronucleus test, determination of cytotoxicity) with selected QPCs confirmed that all of them exhibit cytotoxicity and some even genotoxic potential at elevated concentrations, which emphasizes the need for an emission regulation of these compounds.
