Aqueous Chlorination of D-Limonene.

Limonene (1-methyl-4-(1-methylethenyl)-cyclohexene) is one of the most widespread monocyclic terpenes, being both a natural and industrial compound. It is widely present in the environment, including in water supplies. Therefore, it may be subjected to aqueous chlorination at water treatment stations during drinking water preparation. Besides, being a component of numerous body care and cosmetic products, it may present at high levels in swimming pool waters and could also be subjected to aqueous chlorination. Laboratory experiments with aqueous chlorination of D-limonene demonstrated the prevalence of the conjugated electrophilic addition of HOCl molecule to the double bonds of the parent molecule as the primary reaction. The reaction obeys the Markovnikov rule, as the levels of the corresponding products were higher than those of the alternative ones. Fragmentation pattern in conditions of electron ionization enabled the assigning of the structures for four primary products. The major products of the chlorination are formed by the addition of two HOCl molecules to limonene. The reactions of electrophilic addition are usually accompanied by the reactions of elimination. Thus, the loss of water molecules from the products of various generations results in the reproduction of the double bond, which immediately reacts further. Thus, a cascade of addition-elimination reactions brings the most various isomeric polychlorinated species. At a ratio of limonene/active chlorine higher than 1:10, the final products of aqueous chlorination (haloforms) start forming, while brominated haloforms represent a notable portion of these products due to the presence of bromine impurities in the used NaOCl. It is worth mentioning that the bulk products of aqueous chlorination are less toxic in the bioluminescence test on V. fischeri than the parent limonene.

Transformation of resveratrol under disinfection conditions.

Trans-resveratrol becomes more and more popular all over the world as a powerful antioxidant. Since its positive properties, including antioxidant, anti-inflammatory, anti-tumor are indisputable, nowadays trans-resveratrol is used as a component of various products from nutriceutics to body care formulations, where it is supposed to behave as natural antioxidant and anti-aging compound. It is also added to food packaging materials to increase their stability or/and prevent oxidation. Nevertheless, being released to the environment resveratrol easily forms various transformation products with potentially negative environmental and health effects. The present paper deals with transformation of pure resveratrol and its formulation used as UV-protectors in conditions of aquatic chlorination. Over 80 transformation products were tentatively identified using gas chromatography-high resolution mass spectrometry (GC-HRMS) and ultra pressure liquid chromatography-high resolution mass spectrometry (UPLC-HRMS). Chlorinated phenols and biphenyls are the most relevant among them. Estimation of toxicity of resveratrol products was carried out using luminescent bacteria V. fischeri tests.

Identification of avobenzone by-products formed by various disinfectants in different types of swimming pool waters.

The increased use of sunscreens and other cosmetics containing UV filters causes human and environmental burden. Avobenzone is a widely used UV filter. In its pure form it is known to undergo several transformations including photo-isomerisation, photodegradation, and halogenation. Over 60 disinfection by-products were identified as transformation products of avobenzone in different disinfection reactions of chlorination and bromination in fresh and seawater. Two occasional samples of swimming pool water demonstrated the presence of some of these by-products at noticeable levels as judged by GC-MS peak areas. Although the toxicity of the majority of these products remain unknown, chlorinated phenols and acetophenones are known to be rather toxic. Aquatic bromination of avobenzone resulted in the identification of 33 disinfection by-products (DBPs). Many of them contain bromine in the molecular structure. Addition of copper salt slightly decreases conversion rate simultaneously increasing the levels of major brominated products. Photostability of 3 commercial sunscreen products (solar protection factor 30) containing avobenzone was studied under different experimental conditions including UVA/UVB, UVC photostimulation and chlorination. The commercial sunscreen products have completely different enhancing and inhibitory effect on avobenzone degradation under UVC light. The complex composition of commercial products caused also a protective shield in case of chlorinated solutions of commercial formulations exposed to chlorine and UVA/UVB light at the same time.